Crystals

Editorial

Jump to: Research

2 pages, 164 KiB

Open AccessEditorial

Processing and Characterization of Magnesium-Based Materials

by Domonkos Tolnai

Crystals 2021, 11(2), 96; https://doi.org/10.3390/cryst11020096 - 22 Jan 2021

Cited by 1 | Viewed by 1089

Abstract

Mg-based materials have become increasingly attractive for industries, where weight saving is of importance (e [...] Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

Research

Jump to: Editorial

14 pages, 4788 KiB

Open AccessArticle

Influence of Volume Fraction of Long-Period Stacking Ordered Structure Phase on the Deformation Processes during Cyclic Deformation of Mg-Y-Zn Alloys

by Daria Drozdenko, Gergely Farkas, Pavol Šimko, Klaudia Fekete, Jan Čapek, Gerardo Garcés, Dong Ma, Ke An and Kristián Máthis

Crystals 2021, 11(1), 11; https://doi.org/10.3390/cryst11010011 - 25 Dec 2020

Cited by 11 | Viewed by 2235

Abstract

Deformation mechanisms in extruded Mg-Y-Zn alloys with different volume fractions of the long-period stacking ordered (LPSO) structure have been investigated during cyclic loading, i.e., compression followed by unloading and reverse tensile loading. Electron backscattered diffraction (EBSD) and in situ neutron diffraction (ND) techniques [...] Read more.

Deformation mechanisms in extruded Mg-Y-Zn alloys with different volume fractions of the long-period stacking ordered (LPSO) structure have been investigated during cyclic loading, i.e., compression followed by unloading and reverse tensile loading. Electron backscattered diffraction (EBSD) and in situ neutron diffraction (ND) techniques are used to determine strain path dependence of the deformation mechanisms. The twinning-detwinning mechanism operated in the α-Mg phase is of key importance for the subsequent hardening behavior of alloys with complex microstructures, consisting of α-Mg and LPSO phases. Besides the detailed analysis of the lattice strain development as a function of the applied stress, the dislocation density evolution in particular alloys is determined. Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

► Show Figures

Figure 1

22 pages, 8300 KiB

Open AccessArticle

Restoration Mechanisms at Moderate Temperatures for As-Cast ZK40 Magnesium Alloys Modified with Individual Ca and Gd Additions

by Ricardo Henrique Buzolin, Leandro Henrique Moreno Guimaraes, Julián Arnaldo Ávila Díaz, Erenilton Pereira da Silva, Domonkos Tolnai, Chamini L. Mendis, Norbert Hort and Haroldo Cavalcanti Pinto

Crystals 2020, 10(12), 1140; https://doi.org/10.3390/cryst10121140 - 16 Dec 2020

Cited by 1 | Viewed by 2504

Abstract

The deformation behaviour of as-cast ZK40 alloys modified with individual additions of Ca and Gd is investigated at 250 °C and 300 °C. Compression tests were carried out at 0.0001 s⁻¹ and 0.001 s⁻¹ using a modified Gleeble system during in-situ [...] Read more.

The deformation behaviour of as-cast ZK40 alloys modified with individual additions of Ca and Gd is investigated at 250 °C and 300 °C. Compression tests were carried out at 0.0001 s⁻¹ and 0.001 s⁻¹ using a modified Gleeble system during in-situ synchrotron radiation diffraction experiments. The deformation mechanisms are corroborated by post-mortem investigations using scanning electron microscopy combined with electron backscattered diffraction measurements. The restoration mechanisms in α-Mg are listed as follows: the formation of misorientation spread within α-Mg, the formation of low angle grain boundaries via dynamic recovery, twinning, as well as dynamic recrystallisation. The Gd and Ca additions increase the flow stress of the ZK40, which is more evident at 0.001 s⁻¹ and 300 °C. Dynamic recovery is the predominant restoration mechanism in all alloys. Continuous dynamic recrystallisation only occurs in the ZK40 at 250 °C, competing with discontinuous dynamic recrystallisation. Discontinuous dynamic recrystallisation occurs for the ZK40 and ZK40-Gd. The Ca addition hinders discontinuous dynamic recrystallisation for the investigated temperatures and up to the local achieved strain. Gd addition forms a semi-continuous network of intermetallic compounds along the grain boundaries that withstand the load until their fragmentation, retarding discontinuous dynamic recrystallisation. Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

► Show Figures

Figure 1

18 pages, 9985 KiB

Open AccessArticle

GTN Model-Based Material Parameters of AZ31 Magnesium Sheet at Various Temperatures by Means of SEM In-Situ Testing

by Thorsten Henseler, Shmuel Osovski, Madlen Ullmann, Rudolf Kawalla and Ulrich Prahl

Crystals 2020, 10(10), 856; https://doi.org/10.3390/cryst10100856 - 23 Sep 2020

Cited by 12 | Viewed by 3324

Abstract

Magnesium alloys are primarily associated with complex forming mechanisms, which yield ductility at high temperatures. In sheet metal forming, high triaxiality stress states that favor the ductile damage mechanisms of void formation and growth are known to malleable metals. The formulation of coupled [...] Read more.

Magnesium alloys are primarily associated with complex forming mechanisms, which yield ductility at high temperatures. In sheet metal forming, high triaxiality stress states that favor the ductile damage mechanisms of void formation and growth are known to malleable metals. The formulation of coupled damage models has so far failed, due to the incomplete experimental determination of damage parameters for magnesium AZ31 thin sheet. A quantitative investigation was conducted to determine the ductile damage behavior of twin-roll cast, hot rolled, and annealed AZ31 thin sheet. Results on the mechanisms of void nucleation-, coalescence- and growth-rate were established at temperatures ranging from room temperature to 350 °C. In-situ tensile tests were carried out in a scanning electron microscope with three different specimen types: Simple tension specimens, notched specimens for high triaxiality stress state testing, and shear specimens. Through a comparative analysis of local strains measured by digital image correlation and local void volume fractions determined through post-mortem analysis of specimen cross-sections, GTN (Gurson–Tvergaard–Needleman) model-based material parameters were determined by experiment, representing a novel departure in the magnesium research landscape. The procedure developed in this context should also be transferable to other metals in the form of thin sheets. Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

► Show Figures

Graphical abstract

12 pages, 2972 KiB

Open AccessArticle

Relationship among Initial Texture, Deformation Mechanism, Mechanical Properties, and Texture Evolution during Uniaxial Compression of AZ31 Magnesium Alloy

by Hui Su, Zhibing Chu, Chun Xue, Yugui Li and Lifeng Ma

Crystals 2020, 10(9), 738; https://doi.org/10.3390/cryst10090738 - 21 Aug 2020

Cited by 5 | Viewed by 2461

Abstract

Cuboid samples with significant initial texture differences were cut from extruded AZ31 Mg alloy samples, whose long axis and bar extrusion direction ED were 0° (sample E0), 45° (sample E45), and 90° (sample E90). The relationship among the initial texture, deformation mechanism, mechanical [...] Read more.

Cuboid samples with significant initial texture differences were cut from extruded AZ31 Mg alloy samples, whose long axis and bar extrusion direction ED were 0° (sample E0), 45° (sample E45), and 90° (sample E90). The relationship among the initial texture, deformation mechanism, mechanical properties, and texture evolution of the AZ31 Mg alloy was investigated systematically using a compression test, microstructure characterization, and the Viscoplastic Self-Consistent (VPSC) model. Results revealed a close relationship among them. By influencing the activation of the deformation mechanism, the deformation under different initial textures resulted in obvious mechanical anisotropy. Compared with E0 and E90, the initial texture of E45 was more conducive to the improvement of reforming ability after pre-compression. Meanwhile, the initial texture significantly affected the microstructure characteristics of the material, especially the number and morphology of the {10–12} tensile twins. Texture results showed that the priority of deformation mechanism depended on the initial texture and led to the difference in texture evolution. Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

► Show Figures

Graphical abstract

14 pages, 9198 KiB

Open AccessArticle

Thermomechanical Processing of AZ31-3Ca Alloy Prepared by Disintegrated Melt Deposition (DMD)

by Kamineni Pitcheswara Rao, Kalidass Suresh, Yellapregada Venkata Rama Krishna Prasad and Manoj Gupta

Crystals 2020, 10(8), 647; https://doi.org/10.3390/cryst10080647 - 27 Jul 2020

Cited by 5 | Viewed by 1864

Abstract

Mg-3Zn-1Al (AZ31) alloy is a popular wrought alloy, and its mechanical properties could be further enhanced by the addition of calcium (Ca). The formation of stable secondary phase (Mg,Al)₂Ca enhances the creep resistance at the expense of formability and, therefore, necessitates [...] Read more.

Mg-3Zn-1Al (AZ31) alloy is a popular wrought alloy, and its mechanical properties could be further enhanced by the addition of calcium (Ca). The formation of stable secondary phase (Mg,Al)₂Ca enhances the creep resistance at the expense of formability and, therefore, necessitates the establishment of safe working window(s) for producing wrought products. In this study, AZ31-3Ca alloy has been prepared by the disintegrated melt deposition (DMD) processing route, and its hot deformation mechanisms have been evaluated, and compared with similarly processed AZ31, AZ31-1Ca and AZ31-2Ca magnesium alloys. DMD processing has refined the grain size to 2–3 μm. A processing map has been developed for the temperature range 300–450 °C and strain rate range 0.0003–10 s⁻¹. Three working domains are established in which dynamic recrystallization (DRX) readily occurs, although the underlying mechanisms of DRX differ from each other. The alloy exhibits flow instability at lower temperatures and higher strain rates, which manifests as adiabatic shear bands. A comparison of the processing maps of these alloys revealed that the hot deformation mechanisms have not changed significantly by the increase of Ca addition. Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

► Show Figures

Figure 1

9 pages, 4130 KiB

Open AccessArticle

Microstructure Evolution and Mechanical Properties of AZ31 Magnesium Alloy Sheets Prepared by Low-Speed Extrusion with Different Temperature

by Wenyan Zhang, Hua Zhang, Lifei Wang, Jianfeng Fan, Xia Li, Lilong Zhu, Shuying Chen, Hans Jørgen Roven and Shangzhou Zhang

Crystals 2020, 10(8), 644; https://doi.org/10.3390/cryst10080644 - 26 Jul 2020

Cited by 16 | Viewed by 3033

Abstract

AZ31 magnesium alloy sheets were prepared by low-speed extrusion at different temperatures, i.e., 350 °C, 400 °C, and 450 °C. The microstructure evolution and mechanical properties of extruded AZ31 magnesium alloy sheets were studied. Results indicate that the low-speed extrusion obviously improved the [...] Read more.

AZ31 magnesium alloy sheets were prepared by low-speed extrusion at different temperatures, i.e., 350 °C, 400 °C, and 450 °C. The microstructure evolution and mechanical properties of extruded AZ31 magnesium alloy sheets were studied. Results indicate that the low-speed extrusion obviously improved the microstructure of magnesium alloys. As the extrusion temperature decreased, the grain size for the produced AZ31 magnesium alloy sheets decreased, and the (0001) basal texture intensity of the extruded sheets increased. The yield strength and tensile strength of the extruded sheets greatly increased as the extrusion temperature decreased. The AZ31 magnesium alloy sheet prepared by low-speed extrusion at 350 °C exhibited the finest grain size and the best mechanical properties. The average grain size, yield strength, tensile strength, and elongation of the extruded sheet prepared by low-speed extrusion at 350 °C were ~2.7 μm, ~226 MPa, ~353 MPa, and ~16.7%, respectively. These properties indicate the excellent mechanical properties of the extruded sheets prepared by low-speed extrusion. The grain refinement effect and mechanical properties of the extruded sheets produced in this work were obviously superior to those of magnesium alloys prepared using traditional extrusion or rolling methods reported in other related studies. Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

► Show Figures

Figure 1

13 pages, 3363 KiB

Open AccessArticle

Anisotropic Plastic Behavior in an Extruded Long-Period Ordered Structure Mg₉₀Y_6.5Ni_3.5 (at.%) Alloy

by Gerardo Garces, Rafael Barea, Andreas Stark and Norbert Schell

Crystals 2020, 10(4), 279; https://doi.org/10.3390/cryst10040279 - 7 Apr 2020

Cited by 4 | Viewed by 1983

Abstract

The Mg₉₀Y_6.5Ni_3.5 alloy composed almost completely of the Long-Period-Stacking-Ordered (LPSO) phase has been prepared by casting and extrusion at high temperature. An elongated microstructure is obtained where the LPSO phase with 18R crystal structure is oriented with its [...] Read more.

The Mg₉₀Y_6.5Ni_3.5 alloy composed almost completely of the Long-Period-Stacking-Ordered (LPSO) phase has been prepared by casting and extrusion at high temperature. An elongated microstructure is obtained where the LPSO phase with 18R crystal structure is oriented with its basal plane parallel to the extrusion direction. Islands of α-magnesium are located between the LPSO grains. The mechanical properties of the alloy are highly anisotropic and depend on the stress sign as well as the relative orientation between the stress and the extrusion axes. The alloy is stronger when it is compressed along the extrusion direction. Under this configuration, the slip of <a> dislocations in the basal plane is highly limited. However, the activation of kinking induces an increase in the plastic deformation. In the transversal extrusion direction, some grains deform by the activation of basal slip. The difference in the yield stress between the different stress configurations decreases with the increase in the test temperature. The evolution of internal strains obtained during in-situ compressive experiments reveals that tensile twinning is not activated in the LPSO phase. Full article

(This article belongs to the Special Issue Processing and Characterization of Magnesium-Based Materials)

► Show Figures