Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
4.4
2.9
Journals
Metals
Special Issues
Mechanical Behavior of Metallic Materials under Different Loading Conditions
share announcement

Mechanical Behavior of Metallic Materials under Different Loading Conditions

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Failure Analysis".

Deadline for manuscript submissions: closed (30 September 2022) | Viewed by 30869

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Martin Heilmaier

E-Mail Website
Guest Editor
Materials Science & Engineering, Metallic Materials, Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
Interests: high temperature alloys; intermetallics; high entropy alloys; strengthening mechanisms; creep; directional solidification; powder metallurgy
Prof. Dr. Martina Zimmermann

E-Mail Website1 Website2
Guest Editor
1. Fraunhofer Institute for Material and Beam Technology, Dresden, Germany
2. Technical University Dresden, Dresden, Germany
Interests: deformation behavior of metals and composites; fatigue behavior; microstructure/Properties correlation; damage mechanisms; failure analysis; lightweight structures and joinings

Special Issue Information

Dear Colleagues,

Metallic materials are most frequently used in structural applications under various loading conditions. This Special Issue is dedicated to Prof. Hans-Jürgen Christ, University Siegen, Germany, who, throughout his career, has made seminal contributions to the fatigue and fracture of metals and alloys at various loading rates, temperatures, and within harsh environments. Therefore, we seek contributions that present new results and findings on the deformation behavior of single- and multi-phase (particle-strengthened) metallic materials, including metal matrix composites, particularly research addressing underlying microstructural mechanisms and consequences of material design and application. In addition, papers that address monotonic and cyclic deformation behavior (including the VHCF regime) at low and elevated temperatures in various environments, and studies on fracture mechanisms, are welcome.

Prof. Dr. Martin Heilmaier
Prof. Dr. Martina Zimmermann
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • metals
  • alloys
  • particle strengthening
  • fatigue (LCF, HCF, VHCF)
  • creep
  • fracture mode

Published Papers (17 papers)

Download All Papers
Order results
Result details
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:

Research

12 pages, 4444 KiB  
Article
Influence of a Pronounced Pre-Deformation on the Attachment of Melt Droplets and the Fatigue Behavior of Laser-Cut AISI 304
by André T. Zeuner, Thomas Wanski, Sebastian Schettler, Jonas Fell, Andreas Wetzig, Robert Kühne, Sarah C. L. Fischer and Martina Zimmermann
Metals 2023, 13(2), 201; https://doi.org/10.3390/met13020201 - 19 Jan 2023
Cited by 2 | Viewed by 1073
Abstract
Laser cutting is a suitable manufacturing method for generating complex geometries for sheet metal components. However, their cyclic load capacity is reduced compared to, for example, milled components. This is due to the influence of the laser-cut edge, whose characteristic features act as [...] Read more.
Laser cutting is a suitable manufacturing method for generating complex geometries for sheet metal components. However, their cyclic load capacity is reduced compared to, for example, milled components. This is due to the influence of the laser-cut edge, whose characteristic features act as crack initiation sites, especially resolidified material in the form of burr and melt droplets. Since sheet metal components are often formed into their final geometry after cutting, another important factor influencing fatigue behavior is the effect of the forming process on the laser-cut edge. In particular, the effect of high degrees of deformation has not yet been researched in detail. Accordingly, sheets of AISI 304 were processed by laser cutting and pre-deformed. In the process, α’-martensite content was set to be comparable despite different degrees of deformation. It was found that deformation to high elongations caused a large part of the melt adhesions to fall off, but those still attaching were partially detached and thus formed an initial notch for crack initiation. This significantly lowered the fatigue strength. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

11 pages, 4394 KiB  
Article
Very High Cycle Fatigue Behavior of Austenitic Stainless Steels with Different Surface Morphologies
by Marek Smaga, Annika Boemke, Dietmar Eifler and Tilmann Beck
Metals 2022, 12(11), 1877; https://doi.org/10.3390/met12111877 - 3 Nov 2022
Cited by 4 | Viewed by 1901
Abstract
The fatigue behavior of the two austenitic stainless steels AISI 904L and AISI 347 with different surface morphologies, (i) conventionally turned and finally polished, (ii) cryogenic turned using CO2 snow, as well as (iii) cryogenic turned and finally polished, was investigated using [...] Read more.
The fatigue behavior of the two austenitic stainless steels AISI 904L and AISI 347 with different surface morphologies, (i) conventionally turned and finally polished, (ii) cryogenic turned using CO2 snow, as well as (iii) cryogenic turned and finally polished, was investigated using an ultrasonic fatigue testing system up to the very high cycle fatigue regime using an ultrasonic fatigue testing system. The AISI 904L is stable against deformation-induced phase formation while the AISI 347 is in the metastable state and shows martensite formation induced by cryogenic turning as well as mechanical loading. For the detailed characterization of the surface morphology, confocal microscopy, scanning electron microscopy, and X-ray diffraction methods were used. The specimens from stable austenite failed in the high cycle fatigue and very high cycle fatigue regime. Opposed to this, the metastable austenite achieved true fatigue limits up to load cycle N = 1 × 109 and failed only in the high cycle fatigue regime. Furthermore, due to surface modification, an increase of fatigue strength of metastable AISI 347 was observed. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Graphical abstract

14 pages, 2974 KiB  
Article
In-Situ Characterization of Microstructural Changes in Alloy 718 during High-Temperature Low-Cycle Fatigue
by Sebastian Barton, Maximilian K.-B. Weiss and Hans Jürgen Maier
Metals 2022, 12(11), 1871; https://doi.org/10.3390/met12111871 - 2 Nov 2022
Cited by 1 | Viewed by 1501
Abstract
Components made of nickel-based alloys are typically used for high-temperature applications because of their high corrosion resistance and very good creep and fatigue strength, even at temperatures around 1000 °C. Corrosive damage can significantly reduce the mechanical properties and the expected remaining service [...] Read more.
Components made of nickel-based alloys are typically used for high-temperature applications because of their high corrosion resistance and very good creep and fatigue strength, even at temperatures around 1000 °C. Corrosive damage can significantly reduce the mechanical properties and the expected remaining service life of components. In the present study, a new method was introduced to continuously determine the change in microstructure occurring as a result of exposure to high temperature and cyclic mechanical loading. For this purpose, the conventional low-cycle fatigue test procedure was modified and a non-destructive, electromagnetic testing technique was integrated into a servohydraulic test rig to monitor the microstructural changes. The measured values correlate with the magnetic material properties of the specimen, allowing the microstructural changes in the specimen’s subsurface zone to be analyzed upon high-temperature fatigue. Specifically, it was possible to show how different loading parameters affect the maximum chromium depletion as well as the depth of chromium depletion, which influences the magnetic properties of the nickel-based material. It was also observed that specimen failure is preceded by a certain degree of microstructural change in the subsurface zone. Thus, the integration of the testing technology into a test rig opens up new possibilities for improved prediction of fatigue failure via the continuous recording of the microstructural changes. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

21 pages, 7951 KiB  
Article
Crashworthiness Analysis of Square Aluminum Tubes Subjected to Oblique Impact: Experimental and Numerical Study on the Initial Contact Effect
by Konstantina D. Karantza and Dimitrios E. Manolakos
Metals 2022, 12(11), 1862; https://doi.org/10.3390/met12111862 - 1 Nov 2022
Cited by 8 | Viewed by 1527
Abstract
This study investigates the crashworthiness behavior of square aluminum thin-walled tubes subjected to both axial and oblique impact loading, emphasizing the effects of crushing angle and initial contact between impactor and tube on the plastic collapse initiation and energy absorption capacity. A parametric [...] Read more.
This study investigates the crashworthiness behavior of square aluminum thin-walled tubes subjected to both axial and oblique impact loading, emphasizing the effects of crushing angle and initial contact between impactor and tube on the plastic collapse initiation and energy absorption capacity. A parametric study in crushing angle is conducted until 15°, while the two examined types of initial contact between impactor and tube consist of a contact-in-edge case and a contact-in-corner one, aiming to capture the effect of initial contact on both plastic collapse and energy absorption. Both experimental quasi-static tests and numerical simulation via finite element modeling in LS-DYNA software are carried out for the evaluation of the crushing response of the tested tubes. The 5° oblique cornered crushing revealed the greatest energy absorption, reflecting the most efficient loading case as significant tearing failure occurred around the tube corners in axial crushing due to a higher peak crushing force, while the increase in crushing angle caused a drop in energy absorption and peak force regarding the oblique loading. Finally, an initial contact-in-corner case revealed higher energy absorption compared to both axial and edged oblique loading, while peak force showed a slight decrease with crushing angle in that case. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

13 pages, 6425 KiB  
Article
Surface or Internal Fatigue Crack Initiation during VHCF of Tempered Martensitic and Bainitic Steels: Microstructure and Frequency/Strain Rate Dependency
by Ulrich Krupp and Alexander Giertler
Metals 2022, 12(11), 1815; https://doi.org/10.3390/met12111815 - 26 Oct 2022
Cited by 2 | Viewed by 1657
Abstract
By means of comparing the VHCF response of heat-treated alloy steel, several factors governing the transition from surface (type I) to internal (type II) VHCF failure, and, in the case of internal inclusion and non-inclusion type II VHCF failure, are discussed: differences in [...] Read more.
By means of comparing the VHCF response of heat-treated alloy steel, several factors governing the transition from surface (type I) to internal (type II) VHCF failure, and, in the case of internal inclusion and non-inclusion type II VHCF failure, are discussed: differences in strength, differences in grain size and strength gradients. Therefore, the steel grades (i) 50CrMo4 (0.5 wt%C–1.0 wt%Cr–0.2 wt%Mo) in two different tempering conditions (37HRC and 57HRC) but of the same prior austenite grain size, and (ii) 16MnCrV7 7 (0.16 wt%C–1.25 wt%Mn–1.7 wt%Cr) in the bainitic and martensitic thermomechanical treatment state, were studied. It is concluded that steels of moderate strength (37HRC) exhibit a real endurance limit (109 cycles), while the fatigue strength of high strength (43–57HRC) or coarse-grained steels (37HRC) decreases with increasing number of load cycles. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

20 pages, 8322 KiB  
Article
Influence of Surface Mechanical Attrition Treatment (SMAT) on Microstructure, Tensile and Low-Cycle Fatigue Behavior of Additively Manufactured Stainless Steel 316L
by Thomas Wegener, Tao Wu, Fei Sun, Chong Wang, Jian Lu and Thomas Niendorf
Metals 2022, 12(9), 1425; https://doi.org/10.3390/met12091425 - 29 Aug 2022
Cited by 4 | Viewed by 2316
Abstract
Direct Energy Deposition (DED), as one common type of additive manufacturing, is capable of fabricating metallic components close to net-shape with complex geometry. Surface mechanical attrition treatment (SMAT) is an advanced surface treatment technology which is able to yield a nanostructured surface layer [...] Read more.
Direct Energy Deposition (DED), as one common type of additive manufacturing, is capable of fabricating metallic components close to net-shape with complex geometry. Surface mechanical attrition treatment (SMAT) is an advanced surface treatment technology which is able to yield a nanostructured surface layer characterized by compressive residual stresses and work hardening, thereby improving the fatigue performances of metallic specimens. In the present study, stainless steel 316L specimens were fabricated by DED and subsequently surface treated by SMAT. Both uniaxial tensile tests and uniaxial tension-compression low-cycle fatigue tests were conducted for as-built and SMAT processed specimens. The microstructure of both conditions was characterized by roughness and hardness measurements, scanning electron microscopy and transmission electron microscopy. After SMAT, nanocrystallites and microtwins were found in the top surface layer. These microstructural features contribute to superior properties of the treated surfaces. Finally, it can be concluded that the mechanical performance of additively manufactured steel under static and fatigue loading can be improved by the SMAT process. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

14 pages, 4207 KiB  
Article
Influence of Plastic Strain Control on Martensite Evolution and Fatigue Life of Metastable Austenitic Stainless Steel
by Matthias Droste, Sebastian Henkel, Horst Biermann and Anja Weidner
Metals 2022, 12(7), 1222; https://doi.org/10.3390/met12071222 - 19 Jul 2022
Cited by 2 | Viewed by 1449
Abstract
Metastable austenitic stainless steel was investigated during fatigue tests under strain control with either constant total or constant plastic strain amplitude. Two different material conditions with coarse-grained and ultrafine-grained microstructure were in focus. The influence of plastic strain control of the fatigue test [...] Read more.
Metastable austenitic stainless steel was investigated during fatigue tests under strain control with either constant total or constant plastic strain amplitude. Two different material conditions with coarse-grained and ultrafine-grained microstructure were in focus. The influence of plastic strain control of the fatigue test on both the martensitic phase transformation as well as on the fatigue lives is discussed. In addition, an approach for calculating the Coffin–Manson–Basquin parameters to estimate fatigue lives based on strain-controlled tests at constant total strain amplitudes is proposed for materials undergoing a strong secondary hardening due to martensitic phase transformation. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

18 pages, 16065 KiB  
Article
Characterization of the Isothermal and Thermomechanical Fatigue Behavior of a Duplex Steel Considering the Alloy Microstructure
by Steven Schellert, Julian Müller, Arne Ohrndorf, Bronslava Gorr, Benjamin Butz and Hans-Jürgen Christ
Metals 2022, 12(7), 1161; https://doi.org/10.3390/met12071161 - 7 Jul 2022
Viewed by 1215
Abstract
Isothermal and thermomechanical fatigue behavior of duplex stainless steel (DSS) X2CrNiMoN22-5-3 was investigated. The aim of this work was to understand the fatigue behavior by correlation of the isothermal and thermomechanical fatigue behavior with microstructural observations. Fatigue tests at plastic-strain-amplitude of 0.2% were [...] Read more.
Isothermal and thermomechanical fatigue behavior of duplex stainless steel (DSS) X2CrNiMoN22-5-3 was investigated. The aim of this work was to understand the fatigue behavior by correlation of the isothermal and thermomechanical fatigue behavior with microstructural observations. Fatigue tests at plastic-strain-amplitude of 0.2% were carried out at 20, 300 and 600 °C, while in-phase (IP) and out-of-phase (OP) thermomechanical fatigue (TMF) experiments were performed between 300 and 600 °C. During the 20 °C fatigue test, a continuous softening was observed. Transmission electron microscopy examinations reveal pronounced planar slip behavior in austenite. At 300 °C, deformation concentrates in the ferrite, where strong interactions between CrxN and dislocations were observed that explain the pronounced cyclic hardening. DSS studied exhibits softening throughout the whole isothermal fatigue test at 600 °C. In ferrite, during the 600 °C fatigue test, the G phase, γ′ austenite precipitated, and an unordered dislocation arrangement was observed. The stress responses of the TMF tests can be correlated to those of the isothermal fatigue tests. In IP mode, a positive mean stress resulted in premature failure. No γ′ austenite but the formation of subgrains in the ferrite phase was observed after TMF tests. The plastic deformation of the austenite at high temperatures results in an unordered dislocation arrangement. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

18 pages, 4386 KiB  
Article
Effects of Non-Metallic Inclusions and Mean Stress on Axial and Torsion Very High Cycle Fatigue of SWOSC-V Spring Steel
by Ulrike Karr, Bernd M. Schönbauer, Yusuke Sandaiji and Herwig Mayer
Metals 2022, 12(7), 1113; https://doi.org/10.3390/met12071113 - 28 Jun 2022
Cited by 4 | Viewed by 1739
Abstract
Inclusion-initiated fracture in high-strength spring steel is studied for axial and torsion very high cycle fatigue (VHCF) loading at load ratios of R = −1, 0.1 and 0.35. Ultrasonic S-N tests are performed with SWOSC-V steel featuring intentionally increased numbers and sizes of [...] Read more.
Inclusion-initiated fracture in high-strength spring steel is studied for axial and torsion very high cycle fatigue (VHCF) loading at load ratios of R = −1, 0.1 and 0.35. Ultrasonic S-N tests are performed with SWOSC-V steel featuring intentionally increased numbers and sizes of non-metallic inclusions. The fatigue limit for axial and torsion loading is considered the threshold for mode I cracks starting at internal inclusions. The influence of inclusion size and Vickers hardness on cyclic strength is well predicted with Murakami and Endo’s area parameter model. In the presence of similarly sized inclusions, stress biaxiality is considered by a ratio of torsion to axial fatigue strength of 0.86. Load ratio sensitivity is accounted for by the factor ((1 − R)/2)α, with α being 0.41 for axial and 0.55 for torsion loading. VHCF properties under torsion loading cannot appropriately be deduced from axial data. In contrast to axial loading, the defect sensitivity for torsion loading increases significantly with superimposed static mean load, and no inclusion-initiated fracture is found at R = −1. Size effects and the stress gradient effective under torsion loading are considered to explain smaller crack initiating inclusions found in torsion ultrasonic fatigue tests. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

16 pages, 10503 KiB  
Article
Influence of Residual Stresses on the Crack Initiation and Short Crack Propagation in a Martensitic Spring Steel
by Anna Wildeis, Hans-Jürgen Christ and Robert Brandt
Metals 2022, 12(7), 1085; https://doi.org/10.3390/met12071085 - 24 Jun 2022
Cited by 7 | Viewed by 1798
Abstract
The crack initiation and short crack propagation in a martensitic spring steel were investigated by means of in-situ fatigue testing. Shot peened samples as well as untreated samples were exposed to uniaxial alternating stress to analyze the impact of compressive residual stresses. The [...] Read more.
The crack initiation and short crack propagation in a martensitic spring steel were investigated by means of in-situ fatigue testing. Shot peened samples as well as untreated samples were exposed to uniaxial alternating stress to analyze the impact of compressive residual stresses. The early fatigue damage started in both sample conditions with the formation of slip bands, which subsequently served as crack initiation sites. Most of the slip bands and, correspondingly, most of the short fatigue cracks initiated at or close to prior austenite grain boundaries. The observed crack density of the emerging network of short cracks increased with the number of cycles and with increasing applied stress amplitudes. Furthermore, the prior austenite grain boundaries acted as obstacles to short crack propagation in both sample conditions. Compressive residual stresses enhanced the fatigue strength, and it is assumed that this beneficial effect was due to a delayed transition from short crack propagation to long crack propagation and a shift of the crack initiation site from the sample surface to the sample interior. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

11 pages, 3672 KiB  
Article
Effect of Wall Thickness and Surface Conditions on Creep Behavior of a Single-Crystal Ni-Based Superalloy
by Selina Körber, Silas Wolff-Goodrich, Rainer Völkl and Uwe Glatzel
Metals 2022, 12(7), 1081; https://doi.org/10.3390/met12071081 - 24 Jun 2022
Cited by 5 | Viewed by 1458
Abstract
The influence of wall thickness and specimen surface on the creep behavior of the single-crystal nickel-based superalloy MAR M247LC is studied. Specimens with wall thicknesses of 0.4, 0.8, 1 and 2 mm, with and without casting surface, are compared to specimens of the [...] Read more.
The influence of wall thickness and specimen surface on the creep behavior of the single-crystal nickel-based superalloy MAR M247LC is studied. Specimens with wall thicknesses of 0.4, 0.8, 1 and 2 mm, with and without casting surface, are compared to specimens of the same wall thickness prepared from bulk material. Creep behavior turned out to be independent from surface conditions even for the thinnest specimens. The thickness debit effect is not pronounced for short creep rupture times (≤100 h at 980 °C), whereas it is significant for creep rupture times longer than ~200 h at 980 °C. The thickness debit effect is time-dependent and caused by oxidation and diffusion-controlled mechanisms. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

14 pages, 2796 KiB  
Article
A New Approach to Estimate the Fatigue Limit of Steels Based on Conventional and Cyclic Indentation Testing
by David Görzen, Pascal Ostermayer, Patrick Lehner, Bastian Blinn, Dietmar Eifler and Tilmann Beck
Metals 2022, 12(7), 1066; https://doi.org/10.3390/met12071066 - 22 Jun 2022
Cited by 7 | Viewed by 1886
Abstract
For a reliable design of structural components, valid information about the fatigue strength of the material used is a prerequisite. As the determination of the fatigue properties, and especially the fatigue limit σw, requires a high experimental effort, efficient approaches to [...] Read more.
For a reliable design of structural components, valid information about the fatigue strength of the material used is a prerequisite. As the determination of the fatigue properties, and especially the fatigue limit σw, requires a high experimental effort, efficient approaches to estimate the fatigue strength are of great interest. Available estimation approaches using monotonic properties, e.g., Vickers hardness (HV), and in some cases the cyclic yield strength, only allow a rough estimation of σw. The approaches solely based on monotonic properties lead to substantial deviations of the estimated σw in relation to the experimentally determined fatigue limit as they do not consider the cyclic deformation behavior. In this work, an estimation approach was developed, which is based on a correlation analysis of the fatigue limit σw, HV, and the cyclic hardening potential obtained in instrumented cyclic indentation tests (CIT). For this, eleven conditions from five different low-alloy steels were investigated. The CIT enable an efficient and quantitative determination of the cyclic hardening potential, i.e., the cyclic hardening exponentCHT eII, and thus, the consideration of the cyclic deformation behavior in an estimation approach. In this work, a strong correlation of σw with the product of HV and |eII| was observed. In relation to an existing estimation approach based solely on HV, considering the combination of HV and |eII| enables the estimation of σw with an enormously increased precision. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

12 pages, 30315 KiB  
Article
VHCF Behavior of Inconel 718 in Different Heat Treatment Conditions in a Hot Air Environment
by Sebastian Schöne, Sebastian Schettler, Martin Kuczyk, Martin Zawischa and Martina Zimmermann
Metals 2022, 12(7), 1062; https://doi.org/10.3390/met12071062 - 21 Jun 2022
Cited by 2 | Viewed by 1180
Abstract
The very high cycle properties of Inconel 718 in two different heat treatment conditions were investigated at a test temperature of 500 °C. One condition was optimized for fatigue strength and displayed a finer-grained microstructure, while the second batch had a more coarse-grained [...] Read more.
The very high cycle properties of Inconel 718 in two different heat treatment conditions were investigated at a test temperature of 500 °C. One condition was optimized for fatigue strength and displayed a finer-grained microstructure, while the second batch had a more coarse-grained microstructure. For the high-temperature ultrasonic fatigue testing, a new test concept was developed. The method is based on the principle of a hot-air furnace and thus differs from the conventionally used induction heaters. The concept could be successfully evaluated in the course of the investigations. The materials’ microstructure was analyzed before and after fatigue testing by means of metallographic and electron backscatter diffraction (EBSD)analysis. The results show a significant influence of the heat treatment on the fatigue strength caused by the specific microstructure. Further, a difference in crack propagation behavior due to microstructural influences and non-metallic precipitations was observed. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

12 pages, 8601 KiB  
Article
Comparison of the Internal Fatigue Crack Initiation and Propagation Behavior of a Quenched and Tempered Steel with and without a Thermomechanical Treatment
by Amin Khayatzadeh, Stefan Guth and Martin Heilmaier
Metals 2022, 12(6), 995; https://doi.org/10.3390/met12060995 - 10 Jun 2022
Cited by 1 | Viewed by 1457
Abstract
Previous studies have shown that a thermomechanical treatment (TMT) consisting of cyclic plastic deformation in the temperature range of dynamic strain aging can increase the fatigue limit of quenched and tempered steels by strengthening the microstructure around non-metallic inclusions. This study considers the [...] Read more.
Previous studies have shown that a thermomechanical treatment (TMT) consisting of cyclic plastic deformation in the temperature range of dynamic strain aging can increase the fatigue limit of quenched and tempered steels by strengthening the microstructure around non-metallic inclusions. This study considers the influence of a TMT on the shape, size and position of crack-initiating inclusions as well as on the internal crack propagation behavior. For this, high cycle fatigue tests on specimens with and without TMT were performed at room temperature at a constant stress amplitude. The TMT increased the average lifetime by about 40%, while there was no effect of the TMT on the form or size of critical inclusions. Surprisingly, no correlation between inclusion size and lifetime could be found for both specimen types. There is also no correlation between inclusion depth and lifetime, which means that the crack propagation stage covers only a small portion of the overall lifetime. The average depth of critical inclusions is considerably higher for TMT specimens indicating that the strengthening effect of the TMT is more pronounced for near-surface inclusions. Fisheye fracture surfaces around the critical inclusions could be found on all tested specimens. With increasing fisheye size, a transition from a smooth to a rather rough and wavy fracture surface could be observed for both specimen types. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

12 pages, 5492 KiB  
Article
The Effect of Temperature and Phase Shift on the Thermomechanical Fatigue of Nickel-Based Superalloy
by Ivo Šulák, Karel Hrbáček and Karel Obrtlík
Metals 2022, 12(6), 993; https://doi.org/10.3390/met12060993 - 10 Jun 2022
Cited by 4 | Viewed by 1729
Abstract
In this paper, the minimum temperature and phase shift effects on the thermo–mechanical fatigue (TMF) behavior of Inconel 713LC are investigated. TMF tests were performed under 0° (in-phase-IP) and +180° (out-of-phase-OP) phase shifts between mechanical strain and temperature. Cylindrical specimens were cycled at [...] Read more.
In this paper, the minimum temperature and phase shift effects on the thermo–mechanical fatigue (TMF) behavior of Inconel 713LC are investigated. TMF tests were performed under 0° (in-phase-IP) and +180° (out-of-phase-OP) phase shifts between mechanical strain and temperature. Cylindrical specimens were cycled at constant mechanical strain amplitude with a strain ratio of Rε = −1. Tests were performed with temperature ranges of 300–900 °C and 500–900 °C. The heating and cooling rate was 5 °C/s. Fatigue hardening/softening curves and fatigue life data were assessed. Results show that out-of-phase loading was less damaging than in-phase loading. Scanning electron microscopy (SEM) examination of metallographic sections indicated that the life-reducing damage mechanism was intergranular cavitation under in-phase loading. Transmission electron microscopy (TEM) revealed honeycomb structures for IP loading. The plastic strain localization into persistent slip bands was typical for OP loading. For out-of-phase loading, fatigue damage appeared to be dominant. The increase in the temperature range led to a significant decrease in fatigue life. The reduction of fatigue life was far more pronounced for out-of-phase loading. This can be ascribed to the accelerated crack propagation at high tensile stress under out-of-phase loading as well as the amount of accommodated plastic strain deformation. Based on the SEM scrutiny of metallographic sections and TEM observations of dislocation arrangement, the prevailing damage mechanisms were documented and the lifetime behavior was accordingly discussed. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

6 pages, 1353 KiB  
Communication
Revealing the Role of Cross Slip for Serrated Plastic Deformation in Concentrated Solid Solutions at Cryogenic Temperatures
by Aditya Srinivasan Tirunilai, Klaus-Peter Weiss, Jens Freudenberger, Martin Heilmaier and Alexander Kauffmann
Metals 2022, 12(3), 514; https://doi.org/10.3390/met12030514 - 17 Mar 2022
Cited by 1 | Viewed by 1686
Abstract
Serrated plastic deformation is an intense phenomenon in CoCrFeMnNi at and below 35 K with stress amplitudes in excess of 100 MPa. While previous publications have linked serrated deformation to dislocation pile ups at Lomer–Cottrell (LC) locks, there exist two alternate models on [...] Read more.
Serrated plastic deformation is an intense phenomenon in CoCrFeMnNi at and below 35 K with stress amplitudes in excess of 100 MPa. While previous publications have linked serrated deformation to dislocation pile ups at Lomer–Cottrell (LC) locks, there exist two alternate models on how the transition from continuous to serrated deformation occurs. One model correlates the transition to an exponential LC lock density–temperature variation. The second model attributes the transition to a decrease in cross-slip propensity based on temperature and dislocation density. In order to evaluate the validity of the models, a unique tensile deformation procedure with multiple temperature changes was carried out, analyzing stress amplitudes subsequent to temperature changes. The analysis provides evidence that the apparent density of LC locks does not massively change with temperature. Instead, the serrated plastic deformation is likely related to cross-slip propensity. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Figure 1

19 pages, 6077 KiB  
Article
Low Cycle Fatigue Performance of Additively Processed and Heat-Treated Ti-6Al-7Nb Alloy for Biomedical Applications
by Maxwell Hein, David Kokalj, Nelson Filipe Lopes Dias, Dominic Stangier, Hilke Oltmanns, Sudipta Pramanik, Manfred Kietzmann, Kay-Peter Hoyer, Jessica Meißner, Wolfgang Tillmann and Mirko Schaper
Metals 2022, 12(1), 122; https://doi.org/10.3390/met12010122 - 8 Jan 2022
Cited by 10 | Viewed by 3103
Abstract
In biomedical engineering, laser powder bed fusion is an advanced manufacturing technology, which enables, for example, the production of patient-customized implants with complex geometries. Ti-6Al-7Nb shows promising improvements, especially regarding biocompatibility, compared with other titanium alloys. The biocompatible features are investigated employing cytocompatibility [...] Read more.
In biomedical engineering, laser powder bed fusion is an advanced manufacturing technology, which enables, for example, the production of patient-customized implants with complex geometries. Ti-6Al-7Nb shows promising improvements, especially regarding biocompatibility, compared with other titanium alloys. The biocompatible features are investigated employing cytocompatibility and antibacterial examinations on Al2O3-blasted and untreated surfaces. The mechanical properties of additively manufactured Ti-6Al-7Nb are evaluated in as-built and heat-treated conditions. Recrystallization annealing (925 °C for 4 h), β annealing (1050 °C for 2 h), as well as stress relieving (600 °C for 4 h) are applied. For microstructural investigation, scanning and transmission electron microscopy are performed. The different microstructures and the mechanical properties are compared. Mechanical behavior is determined based on quasi-static tensile tests and strain-controlled low cycle fatigue tests with total strain amplitudes εA of 0.35%, 0.5%, and 0.8%. The as-built and stress-relieved conditions meet the mechanical demands for the tensile properties of the international standard ISO 5832-11. Based on the Coffin–Manson–Basquin relation, fatigue strength and ductility coefficients, as well as exponents, are determined to examine fatigue life for the different conditions. The stress-relieved condition exhibits, overall, the best properties regarding monotonic tensile and cyclic fatigue behavior. Full article
(This article belongs to the Special Issue Mechanical Behavior of Metallic Materials under Different Loading Conditions)
►▼ Show Figures

Graphical abstract

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-17
Back to TopTop