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Crystals
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Microstructure Characterization and Design of Alloys
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Microstructure Characterization and Design of Alloys

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Metals and Alloys".

Deadline for manuscript submissions: closed (10 August 2022) | Viewed by 67389

Special Issue Editors

Prof. Dr. Maria Cecilia Poletti

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Guest Editor
Institute of Materials Science, Joining and Forming, Graz University of Technology, Kopernikusgasse 24-1, A-8010 Graz, Austria
Interests: plastic deformation of light alloys, steels, Ni based alloys and MMCs; creep behaviour of Cr-steels and Ni alloys; precipitation, dissolution and phase transformation kinetics; control of the microstructure by thermomechanical processing
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Silvana Sommadossi

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Guest Editor
Materials Characterization, Institute for Research in Engineering Sciences and Technologies (IITCI CONICET-UNCo), Comahue National University, Buenos Aires 1400, 8300 Neuquén, Argentina
Interests: phase identification; phase transformation Kinetics; diffusion, trasient liquid phase bonding (TLPB); Pb-free solders; Cu- and Ni-based alloys; intermetallics; characterization techniques
Dr. Ricardo H. Buzolin

E-Mail Website1 Website2
Guest Editor
Christian Doppler Laboratory for Design of High-Performance Alloys by Thermomechanical Processing, Kopernikusgasse 24-1, 8010 Graz, Austria
Interests: mechanical behaviour of materials; mechanical testing; microstructure design; material characterization; materials processing; advanced materials, titanium alloys; magnesium alloys

Special Issue Information

There is a worldwide effort to produce sustainable materials to provide solutions to issues such as recyclability, low carbon emission and polluted-free processing routes. Materials manufacture involves the selection of its chemical composition up to the design of a proper processing route for the desired engineering application. Simultaneously, the enhancement of mechanical properties such as elongation, mechanical strength, creep and fatigue resistance, or thermal, electrical and magnetic properties of alloys are also the goal. Materials behaviour are closely related to its microstructure and reaching its optimum depend on a suitable processing route design. Therefore, characterization techniques are crucial to find the relationships between the materials properties and the microstructure features and phases. In-situ techniques allows the investigation of the kinetics and sequence of microstructure formation. Advanced characterization techniques of diffraction and electron microscopy such as synchrotron sources, high-resolution transmission electron microscopy, or atom probe provide insights that, when combined to conventional characterization techniques, enable to determine the microstructure feature and phases in details.

The purpose of the Special Issue “Microstructure characterization and design of alloys” of Crystals is to provide an international forum for ground-breaking investigations on the design of alloys focused on its microstructure characterization. Scientific contributions on alloy design using computational or experimental approaches, microstructure characterization of alloys using conventional or advanced techniques, the correlations between microstructure and material properties and material properties predictions by using computational tools involving modelling and simulation are welcome to this issue. In addition, articles dealing artificial intelligence materials and its applications to alloy design are also welcome.

Prof. Dr. Maria Cecilia Poletti
Prof. Dr. Silvana Sommadossi
Dr. Ricardo H. Buzolin
Guest Editors

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Keywords

  • Alloy design
  • Processing route (i.e., thermomechanical treatments, additive manufacturing, power metallurgy, bonding process, etc.)
  • Microstructure characterization
  • In-situ techniques and microstructural evolution
  • Advanced characterization techniques
  • Electron microscopy
  • Microstructure prediction (modelling and simulation)
  • Thermodynamic calculations of alloys
  • Precipitation

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Published Papers (24 papers)

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Research

13 pages, 7785 KiB  
Article
Effects of Nb on Elevated-Temperature Properties of Fire-Resistant Steel
by Yadong Li, Rongchun Wan, Xing Wang, Hui Zhao and Xun Gong
Crystals 2022, 12(12), 1842; https://doi.org/10.3390/cryst12121842 - 16 Dec 2022
Cited by 4 | Viewed by 1646
Abstract
Objective: Two kinds of fire-resistant steel with different Nb content (Nb-free and 0.03 wt.%) were prepared for studying the effects of Nb addition on the elevated-temperature strength of fire-resistant steel. Methods: Two stages of heat treatment were carried out on the steels to [...] Read more.
Objective: Two kinds of fire-resistant steel with different Nb content (Nb-free and 0.03 wt.%) were prepared for studying the effects of Nb addition on the elevated-temperature strength of fire-resistant steel. Methods: Two stages of heat treatment were carried out on the steels to obtain different microstructures. Typical microstructures, dislocation, and precipitates morphology of steels were observed by SEM and TEM. The dislocation density was calculated by the X-ray data from the microstructures. High temperature and room temperature mechanical properties of steels were determined by tensile testing. Results: The results showed that the YS of N2-HR steel (addition of 0.03 wt.% Nb) at RT and 600 °C was higher than N1-HR steel (Nb-free) by about 81 and 30 MPa, respectively. This indicates that Nb is an alloying element as effective as Mo in increasing the elevated-temperature strength of fire-resistant steel. The dominant strengthening mechanisms of Nb addition on elevated-temperature yield strength are precipitation strengthening and bainite strengthening. Conclusions: Theoretical analysis shows that there are two precipitation strengthening stages in fire-resistant steel: (1) increasing dislocation density during hot rolling, and (2) blocking dislocation movement and recovery in tensile testing. The results also show that the effect of fine grain strengthening is not obvious at high temperature, but is obvious at room temperature. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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12 pages, 2114 KiB  
Article
Comparative Study of TiMn and TiAlV Alloys via the Nanoindentation Technique
by Shafaq Asrar, Ambreen Azmat, Iftikhar Ahmed Channa, Jaweria Ashfaq, Faraz Sufyan, Sarmad Feroze, Ali Dad Chandio, Muhammad Ali Shar and Abdulaziz Alhazaa
Crystals 2022, 12(11), 1537; https://doi.org/10.3390/cryst12111537 - 28 Oct 2022
Cited by 1 | Viewed by 2486
Abstract
There are two common categories of implants that are used in medical sciences, i.e., orthopedic and dental ones. In this study, dental implant materials are focused such as Ti6Al4V alloys that are used for the replacement of lost teeth due to their high [...] Read more.
There are two common categories of implants that are used in medical sciences, i.e., orthopedic and dental ones. In this study, dental implant materials are focused such as Ti6Al4V alloys that are used for the replacement of lost teeth due to their high strength and biocompatibility. However, they cause infections in nearby tissues due to elemental release (potentially Al and V). Thus, manganese is selected to be incorporated into the alloy since it is also present in the human body in the form of traces. Different sets of implants were produced, i.e., Ti5Mn and Ti10Mn (where 5 and 10 describe the percentage of Mn) by using the powder metallurgy technique. This was followed by characterization techniques, including X-ray fluorescence spectroscopy (XRF), X-ray diffractometer (XRD), optical microscope (OM), and nanoindenter. The very aim of this study is to compare the microstructural evolutions, density, and mechanical properties of reference alloys and the ones produced in this study. Results show the microstructure of Ti6Al4V consists of the alpha (α) and beta (β) phases, while Ti5Mn and Ti10Mn revealed the beta (β) phases. The Ti5Mn alloy showed excellent mechanical properties than that of the Ti6Al4V counterpart. Extensive discussion is presented in light of the observed results. The relative density of Ti5Mn alloy was found to be enhanced than that of reference alloy. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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14 pages, 3791 KiB  
Article
Study on the Influence of Grain Size and Microstructure on the Mechanical Properties of Fe-6.5 wt%Si High Silicon Steel Prepared by CVD Method
by Dongdong Ye, Zhou Xu, Changdong Yin, Yiwen Wu, Jianjun Chen, Rui Chen, Jiabao Pan, Yajuan Chen and Rui Li
Crystals 2022, 12(10), 1470; https://doi.org/10.3390/cryst12101470 - 17 Oct 2022
Viewed by 2009
Abstract
As a soft magnetic material with excellent performance, silicon steel is widely used in motors and transformers, but its mechanical properties drop sharply when the silicon content is too high. Therefore, it is of great significance to study its influence on mechanisms to [...] Read more.
As a soft magnetic material with excellent performance, silicon steel is widely used in motors and transformers, but its mechanical properties drop sharply when the silicon content is too high. Therefore, it is of great significance to study its influence on mechanisms to improve the product quality of silicon steel. In this paper, Fe-6.5 wt%Si silicon steel was prepared by vacuum tube furnace, combined with a metallographic experiment, and scanning electron microscope analysis to explore the influence of silicon infiltration temperature and time on grain and grain boundary size, and the tensile test of silicon infiltration 120 s at 1200 °C was obtained by the tensile test’s extension parameter. Given the difficulty in adjusting the size and structure of grains and grain boundaries in the test, this paper discusses the influence of different microstructures on the mechanical properties of silicon steel through tensile simulation. The tensile results show that grain refinement helps to improve the strength and elongation of silicon steel, and columnar grains can slightly increase their strength but greatly reduce the strain rate of silicon steel. This method can greatly reduce the research and development time of Fe-6.5 wt%Si silicon steel and can be used to improve the comprehensive performance of silicon steel. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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16 pages, 6118 KiB  
Article
The Effect of Microstructural Evolution on the Brazeability of Two-Layer Al Sheets
by Ting Yuan, Mingming Zuo, Zhipeng Yuan, Jingzhen Wang, Zili Liu, Quancheng Zhang and Yiyou Tu
Crystals 2022, 12(10), 1387; https://doi.org/10.3390/cryst12101387 - 29 Sep 2022
Cited by 2 | Viewed by 1678
Abstract
In this study, the microstructural evolution and the interaction between the clad and the core alloys that occurs during the brazing process of two-layer Al sheets with equiaxed grains were examined. The study was carried out using optical microscopy (OM), scanning electron microscopy [...] Read more.
In this study, the microstructural evolution and the interaction between the clad and the core alloys that occurs during the brazing process of two-layer Al sheets with equiaxed grains were examined. The study was carried out using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and glow discharge optical emission spectrometry (GDOES). The effects of microstructure on the brazing performances of two-layer sheets were clarified. Although the grains were fine and equiaxed before brazing, three typical microstructural evolutions happened during brazing, corresponding to three kinds of interactions between the clad and core alloys of the aluminum brazing sheets. In the alloys, which had either relatively uniform grain growth or no grain growth, the interaction between the clad alloy and the core alloy was weak; accordingly, they showed a smooth surface, an even microstructure, faint element mutual diffusion, and eventually good brazeability. Meanwhile, in the alloy with obvious abnormal grain growth (AGG), strain-induced liquid-film migration (SILFM) occurred when the energy was too low to cause strain-induced boundary migration (SIBM). This led to rough and uneven surface morphology, significant mutual diffusion, and surface segregation of elements; eventually, this produced the worst brazeability. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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8 pages, 2438 KiB  
Article
Effects of Quenching Medium on Microstructure and Mechanical Properties of High Chromium Cast Iron
by Yi Li, Peng-Xiao Zhu, Cai Tang and Zhi Sun
Crystals 2022, 12(10), 1332; https://doi.org/10.3390/cryst12101332 - 21 Sep 2022
Cited by 5 | Viewed by 1980
Abstract
The cooling properties of different cooling mediums were studied and heat treatment of high chromium cast iron was carried out by different cooling mediums. The results showed that the maximum cooling rate, cooling rate at 300 °C and the quenching liquid cooling capacity [...] Read more.
The cooling properties of different cooling mediums were studied and heat treatment of high chromium cast iron was carried out by different cooling mediums. The results showed that the maximum cooling rate, cooling rate at 300 °C and the quenching liquid cooling capacity of water at 20 °C was 193.6 °C/s, 88.6 °C/s and 2431.1, respectively. With the increase in PAG concentration, the maximum cooling rate and the cooling rate at 300 °C of the coolant decreased. The microstructure of high chromium cast iron treated by water cooling, 10% PAG coolant and 20% coolant was white carbide + tempered martensite + retained austenite, and its impact toughness and fracture toughness were gradually improved. The water-cooled high chromium cast iron had the highest Rockwell hardness of 66.2 HRC, good wear resistance of 0.6103 g and the greatest friction coefficient of 0.4233, the high chromium cast iron treated with 10% PAG had the best wear resistance of 0.5715 and the lowest friction coefficient 0.4182, the high chromium cast iron treated with 20% PAG had the lowest Rockwell hardness 58.1 HRC and the worst wear resistance 0.8213 g. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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13 pages, 4886 KiB  
Article
Contrasting Effects of Laser Shock Peening on Austenite and Martensite Phase Distribution and Hardness of Nitinol
by Rajesh Dora Tamiridi, Rajendra Goud, Prabhakaran Subramaniyan, Kalainathan Sivaperuman, Anand Kumar Subramaniyan, Indrajit Charit and Srikant Gollapudi
Crystals 2022, 12(9), 1319; https://doi.org/10.3390/cryst12091319 - 18 Sep 2022
Cited by 3 | Viewed by 2143
Abstract
Laser shock peening of cold rolled Nitinol was carried out at high power density (7 and 9 GW/cm2) and high overlap ratio (90%). Tensile surface residual stresses were generated in the peened material. An enhancement in surface microhardness from 351 for [...] Read more.
Laser shock peening of cold rolled Nitinol was carried out at high power density (7 and 9 GW/cm2) and high overlap ratio (90%). Tensile surface residual stresses were generated in the peened material. An enhancement in surface microhardness from 351 for unpeened material to 375 and 394 VHN for the 7 and 9 GW/cm2 samples, respectively, was also observed. However, at a depth of 50 μm, the hardness of the peened material was lower than that of the as-received material. These contrasting observations were attributed to the change in the austenitic phase fraction brought about by laser interactions. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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29 pages, 21098 KiB  
Article
Microstructure Analysis of Al-7 wt% Si Alloy Solidified on Earth Compared to Similar Experiments in Microgravity
by András Roósz, Arnold Rónaföldi, Yuze Li, Nathalie Mangelinck-Noël, Gerhard Zimmermann, Henri Nguyen-Thi, Mária Svéda and Zsolt Veres
Crystals 2022, 12(9), 1226; https://doi.org/10.3390/cryst12091226 - 31 Aug 2022
Cited by 2 | Viewed by 1738
Abstract
During ground-based solidification, buoyancy flow can develop by the density difference in the hypoeutectic type of the alloys, such as Al-7 wt% Si alloy. Buoyancy flow can affect the thermal field, solute distribution in the melt, and the position and amount of the [...] Read more.
During ground-based solidification, buoyancy flow can develop by the density difference in the hypoeutectic type of the alloys, such as Al-7 wt% Si alloy. Buoyancy flow can affect the thermal field, solute distribution in the melt, and the position and amount of the new grains. As solidification is a very complex process, it is not very easy to separate the different effects. Under microgravity conditions, natural convection does not exist or is strongly damped due to the absence of the buoyancy force. Therefore, experiments in microgravity conditions provide unique benchmark data for pure diffusive solidification conditions. Compared to the results of the ground-based and microgravity experiments, it is possible to get information on the effect of gravity (buoyancy force). In the framework of the CETSOL project, four microgravity solidification experiments were performed on grain refined (GF) and non-grain refined Al-7 wt% Si alloy onboard the International Space Station in the Materials Science Laboratory. These experiments aimed to study the effect of the solidification parameters (solid/liquid front velocity vSL, temperature gradient GSL) on the grain structure and dendritic microstructures. The microgravity environment eliminates the melt flow, which develops on Earth due to gravity. Four ground-based (GB) experiments were performed under Earth-like conditions with the same (similar) solidification parameters in a vertical Bridgman-type furnace having four heating zones. The detailed analysis of the grain structure, amount of eutectic, and secondary dendrite arm spacing (SDAS) for different process conditions is reported and compared with the results of the microgravity experiments. GB experiments showed that the microstructure was columnar in the samples that do not contain GF material or in case the solid/liquid (vSL front velocity was slow (0.02 mm/s)). In contrast, in the sample which contained GF material, progressive columnar/equiaxed transition (PCET) was observed at vSL = 0.077 mm/s and GSL = 3.9 K/mm. The secondary (SDAS) dendrite arm spacing follows the well-known power law, SDAS=K[t0]13, where K is a constant, and t0 is the local solidification time for both GB and µg experiments. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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16 pages, 8378 KiB  
Article
Stress Relaxation during Artificial Aging of an AlSi7Cu0.5Mg Cast Alloy
by René Wang, Dinesh Ram, Bernhard Stauder, Ricardo Fernández Gutiérrez, Elisabetta Gariboldi and Maria Cecilia Poletti
Crystals 2022, 12(8), 1168; https://doi.org/10.3390/cryst12081168 - 19 Aug 2022
Cited by 2 | Viewed by 2266
Abstract
After casting and solidification, Al cast cylinder heads undergo a sequence of heat treatments to achieve the desired material properties. This sequence comprises solution heat treatment (SHT), quenching, and artificial aging. Internal stresses are formed due to temperature gradients in the complex geometry [...] Read more.
After casting and solidification, Al cast cylinder heads undergo a sequence of heat treatments to achieve the desired material properties. This sequence comprises solution heat treatment (SHT), quenching, and artificial aging. Internal stresses are formed due to temperature gradients in the complex geometry of the cylinder heads during quenching from the SHT temperature to room temperature. Especially high tensile stresses can produce damage during service. However, part of these internal stresses relaxes during the aging treatment. This work aims to systematically measure the relaxation of the stresses, as well as to phenomenologically model the amount and rate of relaxation. Cast specimens of AlSi7Cu0.5Mg are heat-treated in a furnace before relaxation in a creep testing machine. SHT and SHT plus aging at 180, 200, and 230 °C for 0 h, 0.5 h, 1 h, 4 h, and 6 h are carried out before testing. The relaxation of the stress at constant temperature and strain over 5 h is recorded at three different testing temperatures (180 °C, 200 °C, and 230 °C). The relaxation process is strongly dependent on the testing temperature: at 180 °C and 200 °C the equilibrium stress was already reached after around 1 h, and at 230 °C the equilibrium was reached after 3.5 h. The initial stress values do not influence the relaxation rate. A phenomenological relaxation model is developed to calculate the stress decrement over time and the equilibrium stress in the AlSi7Cu0.5Mg-alloy. The model allows for calculating the levels of residual stress at any time during artificial aging as a function of the thermal history of the alloy, the relaxation temperature, and the initial stress level. Complete relaxation of the initial stress is not reached within 5 h. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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12 pages, 5261 KiB  
Article
Effect of Lost-Foam Casting Process on Properties of Spiral Blade
by Yi Li, Pengxiao Zhu, Cai Tang and Zhi Sun
Crystals 2022, 12(8), 1075; https://doi.org/10.3390/cryst12081075 - 31 Jul 2022
Cited by 2 | Viewed by 1884
Abstract
The wear failure mode of a paver spiral blade was simulated by EDEM software. High-manganese steel, medium chromium alloy steel, and high chromium alloy steel were selected as matrix materials; SiC particles and WC particles were selected as surface particle reinforcement materials; and [...] Read more.
The wear failure mode of a paver spiral blade was simulated by EDEM software. High-manganese steel, medium chromium alloy steel, and high chromium alloy steel were selected as matrix materials; SiC particles and WC particles were selected as surface particle reinforcement materials; and the spiral blade was prepared by the EPC process. The performance and wear mechanism of the spiral blade prepared by EPC were analyzed by microstructure, hardness, impact, pin disk, erosion wear test, and wear morphology. Modeling with EDEM software and applying the discrete element analysis method of particle system could simulate the actual working situation of the spiral blade of the paver well. Through the simulation, it was found that the wear amount of the spiral blade of the paver from the spiral shaft to the outside of the spiral blade was increasing. SiC and WC particle-reinforced wear-resistant coatings were prepared on the surfaces of high-manganese steel, medium chromium alloy steel, and high chromium alloy steel by the EPC method. The wear-resistant coating of high-manganese steel was 5.05 mm, the coating of medium chromium alloy steel was 5.98 mm, and the coating of high chromium alloy steel was 7.02 mm. The higher the chromium content, the better the diffusion with SiC and WC particles. In the process of the wear test, the soft phase in the coating was first worn away and concaved, and the hard phase protruded to bear the wear. After wear, it was found that the sample with high chromium alloy steel as matrix and SiC and WC particles as wear-resistant coating had the best wear resistance. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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21 pages, 14899 KiB  
Article
The Effect of Scandium on the Microstructure of the Aluminium Alloy AA 6086
by Sandi Žist, Matej Steinacher, Tonica Bončina, Mihaela Albu, Jaka Burja, Maja Vončina and Franc Zupanič
Crystals 2022, 12(7), 973; https://doi.org/10.3390/cryst12070973 - 12 Jul 2022
Cited by 5 | Viewed by 2480
Abstract
The investigation studied the effects of 0.2 wt.% and 1 wt.% scandium (Sc) additions on the microstructure of the aluminium alloy AA 6086 in different conditions. The alloys were produced by casting into a metallic mould, followed by various heat treatments. The alloys [...] Read more.
The investigation studied the effects of 0.2 wt.% and 1 wt.% scandium (Sc) additions on the microstructure of the aluminium alloy AA 6086 in different conditions. The alloys were produced by casting into a metallic mould, followed by various heat treatments. The alloys were examined using light microscopy, scanning and transmission electron microscopy, microchemical analysis, differential scanning calorimetry and X-ray diffraction. The phase compositions and solidification sequences were modelled using the CALPHAD approach, which reasonably agreed with the experimental results. The addition of Sc to AA 6086 strongly reduced the grain size of the Al-rich solid solution and induced the appearance of Sc-rich phases AlSc2Si2 and L12-Al3X. Other phases identified in the Sc-free alloy were also found in the Sc-modified alloys. Homogenisation caused the dissolution of most phases and the formation of different types of dispersoids. In the alloy with 0.2% Sc, the distribution of dispersoids was not uniform. The plate-like AlMnCrSi dispersoids formed mainly at the dendrite centres, together with spherical L12 precipitates, while smaller α-AlMnSi and tetragonal t-Al3Zr dispersoids were created elsewhere. The addition of 0.2% Sc did not considerably affect the strengthening of AA 6086. The precipitation during isothermal ageing was slightly delayed and shifted to higher temperatures during continuous heating. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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14 pages, 4513 KiB  
Article
Effect of Forced Melt Flow on Al–Si Eutectic-Alloy Microstructures
by Kassab Al-Omari, András Roósz, Arnold Rónaföldi and Zsolt Veres
Crystals 2022, 12(5), 731; https://doi.org/10.3390/cryst12050731 - 19 May 2022
Cited by 3 | Viewed by 2136
Abstract
Al–Si eutectic alloys are industrially important; they play a significant role in the casting-manufacturing of most materials. The properties of the materials are governed by their microstructure, which can be tuned by adjusting the solidification process parameters. Herein, the effect of forced melt [...] Read more.
Al–Si eutectic alloys are industrially important; they play a significant role in the casting-manufacturing of most materials. The properties of the materials are governed by their microstructure, which can be tuned by adjusting the solidification process parameters. Herein, the effect of forced melt flow on the microstructure of an Al–Si eutectic alloy during unidirectional solidification was investigated experimentally. Al–12.6-wt%-Si alloy samples were solidified in a vertical Bridgman-type furnace equipped with a rotating magnetic inductor to induce flow in the melt. The samples were subjected to different magnetic induction conditions during the solidification experiments. The diameter of the samples was 8 mm, and their length was 120 mm. The eutectic alloy samples were solidified unidirectionally at a growth rate of v ≈ 0.1 mm/s and a temperature gradient of G ≈ 6 K/mm. The inter-lamellar distances (λ), lengths, and orientation angles of the Si lamellae were investigated using new measurement methods. The experimental results reveal that applying the rotating magnetic field (RMF) during the solidification has a distinct effect on the microstructure of Al–Si eutectic alloys. Indeed, the RMF refines the eutectic structure, reduces the interlamellar distances, and increases the diversity of the Si lamella angle’s orientations. However, the successive stirring process has a negligible effect on the lengths and angles of Si lamellae. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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14 pages, 3905 KiB  
Article
Deformation Mechanism and Structural Changes in the Globular Ti-6Al-4V Alloy under Quasi-Static and Dynamic Compression: To the Question of the Controlling Phase in the Deformation of α+β Titanium Alloys
by Pavlo E. Markovsky, Jacek Janiszewski, Olexander Dekhtyar, Matthew Mecklenburg and Sergey V. Prikhodko
Crystals 2022, 12(5), 645; https://doi.org/10.3390/cryst12050645 - 1 May 2022
Cited by 5 | Viewed by 2842
Abstract
The deformation mechanism of the Ti-6Al-4V (wt.%) alloy with globular structure was studied under conditions of quasi-static and high-strain compression with rates 10−3 s−1 and 2.1–3.3 × 103 s−1, respectively. High-strain compression was conducted using a Split Hopkinson [...] Read more.
The deformation mechanism of the Ti-6Al-4V (wt.%) alloy with globular structure was studied under conditions of quasi-static and high-strain compression with rates 10−3 s−1 and 2.1–3.3 × 103 s−1, respectively. High-strain compression was conducted using a Split Hopkinson Pressure Bar (SHPB). The details of the deformation mechanism were evaluated based on the analysis of the deformation hardening curves using the strain hardening exponent concept developed for titanium alloys in tension conditions. The used approach allowed us to identify the stages of plastic deformation observed and the controlling phase in deformation of two-phase alloy through the assessment of the strengthening index, n. It has been found that three deformation stages can be identified in quasi-static conditions. However, when the alloy is compressed at a high strain rate, the third deformation stage does not develop due to the high process rate. Further analysis of deformation curves reveals the leading role of the β-phase under the quasi-static conditions and the essential contribution of the second, α-phase, at a high compression rate. The findings on the deformation mechanism based on the analysis of hardening curves were supported by a detailed structural study. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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18 pages, 31207 KiB  
Article
Microstructure and Properties after Friction Stir Processing of Twin-Roll Cast Al–Mn–Cu–Be Alloy
by Matjaž Macerl, Franc Zupanič, Lara Hočuršćak, Damjan Klobčar, András Kovács and Tonica Bončina
Crystals 2022, 12(5), 630; https://doi.org/10.3390/cryst12050630 - 27 Apr 2022
Cited by 3 | Viewed by 1969
Abstract
We studied the effect of friction stir processing (FSP) on the microstructure and properties of high-speed twin-roll cast strips made of an experimental Al–Mn–Cu–Be alloy. The samples were examined using light, scanning, and transmission electron microscopy, microchemical analysis, X-ray diffraction, and indentation testing. [...] Read more.
We studied the effect of friction stir processing (FSP) on the microstructure and properties of high-speed twin-roll cast strips made of an experimental Al–Mn–Cu–Be alloy. The samples were examined using light, scanning, and transmission electron microscopy, microchemical analysis, X-ray diffraction, and indentation testing. During FSP, the rotational speed varied, while other parameters remained constant. The uniformity of the microstructure increased with the growing rotational speed. In the stir zone, several processes took place, and the most important were: recrystallisation of the matrix grains, fragmentation of the primary intermetallic particles Al15Mn3Be2 and their more uniform distribution in the stir zone, fracture, and dispersion of the eutectic icosahedral quasicrystalline phase (IQC), transformation of tiny Al15Mn3Be2 and IQC particles into the τ1-Al26Mn6Cu4 phase and precipitation of Al–Mn–Cu precipitates. In the thermomechanically affected zone, new dislocations formed as well as dispersion of the IQC eutectic phase and recrystallisation of the matrix grains. In the heat-affected zone, dissolution of θ’-Al2Cu precipitates occurred. The hardness variation was not severe between the stir and heat-affected zones. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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19 pages, 5739 KiB  
Article
The Influence of Microstructure on the Electromagnetic Behavior of Carbon Steel Wires
by Isadora Maria Oliveira Anício Costa, Marianna Batková, Ivan Batko, Abdelkader Benabou, Christophe Mesplont and Jean-Bernard Vogt
Crystals 2022, 12(5), 576; https://doi.org/10.3390/cryst12050576 - 20 Apr 2022
Cited by 8 | Viewed by 3069
Abstract
This paper describes the relations between microstructure, mechanical properties, and electromagnetic behavior of carbon steel wires submitted to different thermomechanical treatments. The electrical resistivity and bulk magnetic properties are determined through resistivity measurements down to 2 K and magnetic hysteresis loop measurements. In [...] Read more.
This paper describes the relations between microstructure, mechanical properties, and electromagnetic behavior of carbon steel wires submitted to different thermomechanical treatments. The electrical resistivity and bulk magnetic properties are determined through resistivity measurements down to 2 K and magnetic hysteresis loop measurements. In addition, magnetic domains are imaged by magnetic force microscopy despite the complex microstructures. The electromagnetic properties are mainly related to changes in the volume fraction, morphology, and distribution of the cementite phase within the α-ferrite matrix. Electrical conductivity and magnetic permeability increase in the order of martensite, tempered martensite, pearlite, proeutectoid ferrite-pearlite, spheroidite, and ferrite microstructures. The increase in carbon concentration enhances the electrons localization at atomic sites, assisting the covalent character of Fe–C interatomic bonds and thereby reducing conductivity. Moreover, the α-Fe3C interfaces that act as a physical barrier for dislocation slip in ferrite, affecting also the main free-paths for conductive electrons and magnetic domain walls displacements within the materials. As the electromagnetic behavior of steels results from individual contributions of microstructural elements that are often intrinsically related to one another, a careful interpretation of both electrical and magnetic responses is critical for a proper application of quality and process monitoring methods of carbon steel wires. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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11 pages, 4575 KiB  
Article
Mechanical and Conductive Performance of Aged 6xxx Aluminum Alloy during Rotary Swaging
by Hongmei Jin, Renguo Guan and Di Tie
Crystals 2022, 12(4), 530; https://doi.org/10.3390/cryst12040530 - 10 Apr 2022
Cited by 11 | Viewed by 2336
Abstract
Thermomechanical treatment consisting of heat treatment and deformation is an effective processing route for precipitation-hardened 6xxx alloy (Al-Mg-Si-Cu system), and precipitates and dislocations produced during the process can significantly change its mechanical and conductive performance. We therefore investigated the microstructural evolution of precipitates [...] Read more.
Thermomechanical treatment consisting of heat treatment and deformation is an effective processing route for precipitation-hardened 6xxx alloy (Al-Mg-Si-Cu system), and precipitates and dislocations produced during the process can significantly change its mechanical and conductive performance. We therefore investigated the microstructural evolution of precipitates in a representative 6xxx alloy during thermomechanical treatment. When the precipitates encountered the accumulated dislocations, the precipitates were bent and broken into dispersed smaller particles. The strength of the alloy was significantly improved by the proliferation of dislocations and precipitates and desired electrical conductivity was obtained as well. Our results prove that peak aging plus cold rotary swaging is an efficient processing route for simultaneously improving the mechanical and conductive performance of 6xxx alloy. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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18 pages, 6051 KiB  
Article
Influence of Solidification Parameters on the Amount of Eutectic and Secondary Arm Spacing of Al–7wt% Si Alloy Solidified under Microgravity
by András Roósz, Arnold Rónaföldi, Yuze Li, Nathalie Mangelinck-Noël, Gerhard Zimmermann, Henri Nguyen-Thi, Mária Svéda and Zsolt Veres
Crystals 2022, 12(3), 414; https://doi.org/10.3390/cryst12030414 - 17 Mar 2022
Cited by 5 | Viewed by 2302
Abstract
During the solidification of hypoeutectic Al–7% Si alloy, density differences develop in the melt due to variations in concentration and temperature. On Earth, melt flow can occur due to gravity, which then affects the solidification process. The microgravity environment strongly eliminates convection in [...] Read more.
During the solidification of hypoeutectic Al–7% Si alloy, density differences develop in the melt due to variations in concentration and temperature. On Earth, melt flow can occur due to gravity, which then affects the solidification process. The microgravity environment strongly eliminates convection in the melt and allows investigation of the solidification process in purely diffusive circumstances. In this study, four solidification experiments were performed on grain-refined and non-grain-refined Al–7 wt% Si alloy on-board the International Space Station (ISS) in the Materials Science Lab (MSL) to study the effect of solidification parameters (solid/liquid front velocity (v) and temperature gradient (G)) on the grain structure and dendritic microstructure. The grain structure has been analyzed in detail in some earlier studies. The aim of this work was to carry out detailed analysis of the macrosegregation caused by the diffusion of Si from the initial mushy zone during the homogenization step and the subsequent solidification phase of the experiments as well as the correlated distribution of eutectic along the solidification direction. The secondary dendrite arm spacing (SDAS) for different process conditions was also studied. For these two issues, microgravity experimental results were compared to simulation results. The macrosegregation was calculated by the finite difference method. Because the steady-state solidification conditions were never reached, the solidification process was characterized by the average front velocity and temperature gradient. Considering the actual liquidus temperature (TL) caused by macrosegregation, the SDAS was calculated as a function of the average processing parameters and the actual liquidus temperature with the classical Kirkwood’s equation. As a result, good agreement was obtained between the calculated and measured SDAS. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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15 pages, 5424 KiB  
Article
Microstructures and Mechanical Properties of Ductile Cast Iron with Different Crystallizer Inner Diameters
by Jiaojiao Bai, Haifeng Xu, Yuhui Wang, Xingpin Chen, Xiaodan Zhang, Wenquan Cao and Yang Xu
Crystals 2022, 12(3), 413; https://doi.org/10.3390/cryst12030413 - 17 Mar 2022
Cited by 10 | Viewed by 7068
Abstract
Five types of ductile cast irons (DCIs) were fabricated by crystallizers with different inner diameters, as well as five different austempered ductile cast irons (ADIs) after the same isothermal quenching process. The effects of amount, diameter, and morphology of graphite on the mechanical [...] Read more.
Five types of ductile cast irons (DCIs) were fabricated by crystallizers with different inner diameters, as well as five different austempered ductile cast irons (ADIs) after the same isothermal quenching process. The effects of amount, diameter, and morphology of graphite on the mechanical properties of DCI and ADI and the effect of the original as-cast microstructure on the microstructure after austempering were studied. The microstructures were characterized by optical microscopy, scanning electron microscopy, and X-ray diffraction. Their mechanical properties were examined by tensile, U-shaped impact, and hardness tests. As the diameter of the crystallizer increases from 60 mm to 150 mm, the diameter of the nodular graphite increases from ~10 to ~50 μm, and the nodularity rate decreases from 100 to 70%. The average ultimate tensile strength increases from ~500 MPa in the as-cast state to 1100 MPa in the austempered state and the hardness increases from ~180 HB to 400 HB. The elongation in cast state decreases from 11 to 4.6% and the elongation in ADI state decreases from 7 to 4.5%. Through the research in this paper, it can be seen that ADIs with different matrix microstructures can be obtained from different original as-cast microstructures through the same isothermal quenching process, and different casting crystallizers can be selected according to different performance requirements, which can reduce the nitrite pollution and reduce cost. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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19 pages, 6475 KiB  
Article
A Comparative Analysis of the Tribological Behavior of Hard Layers Obtained by Three Different Hardened-Surface Processes on the Surface of AISI 4140 Steel
by Pablo Alfredo Ruiz-Trabolsi, Alexis Chino-Ulloa, José Guadalupe Miranda-Hernández, Raúl Tadeo-Rosas, Rafael Carrera-Espinoza, Julio César Velázquez and Enrique Hernández-Sánchez
Crystals 2022, 12(2), 298; https://doi.org/10.3390/cryst12020298 - 20 Feb 2022
Cited by 8 | Viewed by 2815
Abstract
This work compares the tribological behavior of surface layers obtained by three different hardening processes. The layers were formed on the surface of AISI 4140 steel by applying three different thermochemical treatments. Wear resistance was evaluated using a standardized tribological machine for abrasive [...] Read more.
This work compares the tribological behavior of surface layers obtained by three different hardening processes. The layers were formed on the surface of AISI 4140 steel by applying three different thermochemical treatments. Wear resistance was evaluated using a standardized tribological machine for abrasive wear, according to the limits established by the ASTM G65 “Standard Test Method for Measuring Abrasion Using Dry Sand/Rubber Wheel Apparatus”. According to the results, the boride layers exhibited the highest wear resistance, as compared to nitrided and carburized layers. In contrast, the carburized layers presented the highest loss of volume. Scanning electron microscopy (SEM) was used to analyze the worn surfaces to examine the wear mechanisms. Abrasive wear was identified in all the samples, as the main abrasive wear mechanism. The mean values of the coefficient of friction (CoF) of the hardened surfaces were 0.39, 0.55, and 0.65 for carburizing, nitriding, and boriding samples, respectively, indicating that the wear process may not always be related to a low CoF. The results suggest that the highest hardness is normally associated with high wear resistance, but the coefficient of friction could be not directly related to the hardness of the materials. Finally, a statistical study demonstrates the random nature of the layers obtained by three different hardening processes. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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15 pages, 4931 KiB  
Article
Crystallographic Analysis of Plate and Lath Martensite in Fe-Ni Alloys
by Pascal Thome, Mike Schneider, Victoria A. Yardley, Eric J. Payton and Gunther Eggeler
Crystals 2022, 12(2), 156; https://doi.org/10.3390/cryst12020156 - 21 Jan 2022
Cited by 12 | Viewed by 5799
Abstract
In the present work, we use an advanced EBSD method to analyze the two prominent types of martensite microstructures that are found in the binary Fe-Ni system, lath martensite (27.5 at.% Ni) and plate martensite (29.5 at.% Ni). We modify, document, and apply [...] Read more.
In the present work, we use an advanced EBSD method to analyze the two prominent types of martensite microstructures that are found in the binary Fe-Ni system, lath martensite (27.5 at.% Ni) and plate martensite (29.5 at.% Ni). We modify, document, and apply an analytical EBSD procedure, which was originally proposed by Yardley and Payton, 2014. It analyzes the distributions of the three KSI-angles (ξ1, ξ2, and ξ3, KSI after Kurdjumov and Sachs), which describe small angular deviations between crystal planes in the unit cells of martensite and austenite—which are related through specific orientation relationships. The analysis of the angular distributions can be exploited to obtain high-resolution, color-coded micrographs of martensitic microstructures, which, for example, visualize the difference between lath and plate martensite and appreciate the microstructural features, like midribs in large plate martensite crystals. The differences between the two types of martensite also manifest themselves in different distributions of the KSI-angles (wider for lath and narrower for plate martensite). Finally, our experimental results prove that local distortions result in scatter, which is larger than the differences between the orientation relationships of Kurdjumov/Sachs, Nishiyama/Wassermann, and Greninger/Troiano. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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9 pages, 4661 KiB  
Article
Microstructure Evolution of Mg-Sn-Y Alloy Solidified under High Pressure and Temperature Gradient
by Chunming Zou, Rong Zhang, Zunjie Wei and Hongwei Wang
Crystals 2022, 12(2), 149; https://doi.org/10.3390/cryst12020149 - 21 Jan 2022
Cited by 1 | Viewed by 2413
Abstract
The microstructures of Mg-1Sn-2.5Y (wt%) alloys solidified under high pressures were investigated. In addition, a mathematical model was established to analyze the effects of solidification pressure and cooling rate on the average grain size. The results show that the alloy was solidified under [...] Read more.
The microstructures of Mg-1Sn-2.5Y (wt%) alloys solidified under high pressures were investigated. In addition, a mathematical model was established to analyze the effects of solidification pressure and cooling rate on the average grain size. The results show that the alloy was solidified under high pressure and temperature gradient using the cooling rate difference in the high pressure chamber, resulting in the formation of the outer equiaxed zone, the columnar zone, and the equiaxed zone in the sample. With an increase in the solidification pressure, the columnar-to-equiaxed transition was inhibited in Mg-1Sn-2.5Y alloy. In the outer fine equiaxed zone and the columnar zone, the solubility of Sn in the Mg matrix increased with an increase in solidification pressure. The average secondary dendrite arm spacing decreased from 14–17 μm under 1 GPa to 9–11 μm under 1.5 GPa. Increases in pressure and cooling rate resulted in a reduction in average grain size. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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6 pages, 4411 KiB  
Communication
Crystallographic Orientation Relationship between α and β Phases during Non-Equilibrium Heat Treatment of Cu-37 wt. % Zn Alloy
by Akbar Heidarzadeh, Mousa Javidani and Lyne St-Georges
Crystals 2022, 12(1), 97; https://doi.org/10.3390/cryst12010097 - 13 Jan 2022
Cited by 1 | Viewed by 2227
Abstract
The crystallographic orientation relationship between α and β phases during the non-equilibrium heat treatment of a Cu-37 wt. % Zn alloy was investigated. With this aim, Cu-37 wt. % Zn alloy plates with a thickness of 2 mm were heated at 810 °C [...] Read more.
The crystallographic orientation relationship between α and β phases during the non-equilibrium heat treatment of a Cu-37 wt. % Zn alloy was investigated. With this aim, Cu-37 wt. % Zn alloy plates with a thickness of 2 mm were heated at 810 °C for 1 h and then were quenched in water. The microstructure and texture of heat-treated samples were analyzed using optical microscopy and electron backscattered diffraction. By this non-equilibrium heat treatment, β phase was formed on both the grain boundaries and grain interiors. In addition, the Σ3 twin boundaries acted as preferred areas for α→β transformation. The orientation imaging microscopy results revealed a Kurdjumov–Sachs (K–S) orientation relationship between α and β phases. Furthermore, the details of microstructural evolution and texture analysis were discussed. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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10 pages, 3782 KiB  
Article
Effect of Continuous Annealing Temperature on the Microstructure, Mechanical Properties and Texture of Annealed Drawn and Ironed Plate
by Zhiying Mo, Xiaohong Chu, Pengfei Gao, Dengcui Yang, Heng Cui, Yuan Fang, Haixu Li, Xiandong Yin and Zhengzhi Zhao
Crystals 2021, 11(12), 1569; https://doi.org/10.3390/cryst11121569 - 16 Dec 2021
Cited by 6 | Viewed by 3038
Abstract
To improve the production process and produce high-quality annealed drawn and ironed (DI) plate, continuous annealing experiments were carried out at 620 °C, 640 °C, 680 °C, and 720 °C, and the effect of continuous annealing temperature on the microstructure, mechanical characteristics, and [...] Read more.
To improve the production process and produce high-quality annealed drawn and ironed (DI) plate, continuous annealing experiments were carried out at 620 °C, 640 °C, 680 °C, and 720 °C, and the effect of continuous annealing temperature on the microstructure, mechanical characteristics, and texture of annealed DI plate were clarified. The microstructure was tested with a scanning electron microscope (SEM); the mechanical properties and weighted average of the plastic strain ratio (r¯) were measured using a tension test; and the texture characterizations were tested by X-ray powder diffractometer (XRD) and electron backscatter diffraction (EBSD). The results reveal that, with the increase of the annealing temperature, the average grain size grew from 5.14 μm to 6.56 μm, the yield strength and tensile strength decreased, and the elongation increased. The rolling textures drastically reduced after annealing. When annealed at a lower temperature of 620 °C, the texture content of {111} <110> was the highest. When the annealing temperature increased to 640 °C, 680 °C and 720 °C, the texture content of {111} <112> was higher than that of {111} <110>. The mechanical properties of the DI plate that was annealed at 640 °C are the best, with a higher r¯ value and a lower planar anisotropy value. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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28 pages, 35379 KiB  
Article
Influence of V and Zn in FeCrCuMnTi High-Entropy Alloys on Microstructures and Uniaxial Compaction Behavior Prepared by Mechanical Alloying
by Subbarayan Sivasankaran, Fahad A. Al-Mufadi and Hany R. Ammar
Crystals 2021, 11(11), 1413; https://doi.org/10.3390/cryst11111413 - 19 Nov 2021
Cited by 5 | Viewed by 2171
Abstract
The densification behavior of FeCrCuMnTi (HEA1), FeCrCuMnTiV (HEA2), and FeCrCuMnTiVZn (HEA3) equiatomic high-entropy alloys (HEAs) was explored using different uniaxial quasi-static controlled compaction (1 mm/min). These HEAs were synthesized by mechanical alloying (MA, speed: 300 rpm, BPR: 10:1, time: 25 h). Various phase [...] Read more.
The densification behavior of FeCrCuMnTi (HEA1), FeCrCuMnTiV (HEA2), and FeCrCuMnTiVZn (HEA3) equiatomic high-entropy alloys (HEAs) was explored using different uniaxial quasi-static controlled compaction (1 mm/min). These HEAs were synthesized by mechanical alloying (MA, speed: 300 rpm, BPR: 10:1, time: 25 h). Various phase formations, structural characteristics (crystallite size, lattice strain, and lattice constant), thermo-dynamic calculations, powder surface morphologies, detailed microstructural evolutions, and chemical compositions were examined using X-ray diffraction, high-resolution scanning electron microscopy, and high-resolution transmission electron microscopy. The XRD results revealed the formation of multiple solid solutions (FCC, BCC, and HCP) due to the variation in entropy, and the presence of high-strength elements (Cr, Ti, and V) in the developed HEA alloys. The synthesized powders were consolidated into bulk green samples with different compaction pressures starting from 25 to 1100 MPa under as-milled and milled under stress recovery conditions (150 °C, 1 h). The incorporation of V in the FeCrCuMnTi HEA resulted in improved densification due to a greater reduction in particle size, and high configurational entropy. Furthermore, the stress-recovered powder samples produced more relative density owing to the elimination of lattice strain. Several linear and non-linear compaction models were applied to predict densification behavior. The non-linear Cooper and Eaton model produced the highest regression coefficients compared to the other models. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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14 pages, 30764 KiB  
Article
Additive Manufacturing of Compositionally-Graded AISI 316L to CoCrMo Structures by Directed Energy Deposition
by Niklas Sommer, Philipp Kluge, Florian Stredak, Sascha Eigler, Horst Hill, Thomas Niendorf and Stefan Böhm
Crystals 2021, 11(9), 1043; https://doi.org/10.3390/cryst11091043 - 30 Aug 2021
Cited by 7 | Viewed by 3326
Abstract
In the present study, compositionally-graded structures of AISI 316L and CoCrMo alloy are manufactured by powder-based laser-beam directed energy deposition (DED-LB). Through a process-integrated adjustment of powder flow, in situ alloying of the two materials becomes feasible. Thus, a sharp and a smooth [...] Read more.
In the present study, compositionally-graded structures of AISI 316L and CoCrMo alloy are manufactured by powder-based laser-beam directed energy deposition (DED-LB). Through a process-integrated adjustment of powder flow, in situ alloying of the two materials becomes feasible. Thus, a sharp and a smooth transition with a mixture of both alloys can be realized. In order to investigate the phase formation during in situ alloying, a simulation approach considering equilibrium calculations is employed. The findings reveal that a precise compositional as well as functional gradation of the two alloys is possible. Thereby, the chemical composition can be directly correlated with the specimen hardness. Moreover, phases, which are identified by equilibrium calculations, can also be observed experimentally using scanning electron microscopy (SEM) and energy-dispersive X-ray-spectroscopy (EDS). Electron backscatter diffraction (EBSD) reveals epitaxial grain growth across the sharp transition region with a pronounced <001>-texture, while the smooth transition acts as nucleus for the growth of new grains with <101>-orientation. In light of envisaged applications in the biomedical sector, the present investigation demonstrates the high potential of an AISI 316L/CoCrMo alloy material combination. Full article
(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)
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