The Effect of Initial Texture on Deformation Behaviors of Mg Alloys Under Erichsen Test
11 Mar 2018-pp 223-229
TL;DR: In this paper, the role of difference in initial textures and grain sizes in Mg alloys sheets was investigated to understand the deformation and fracture mechanisms in mg alloy during Erichsen test and the evolution of the microstructure and microtexture of the deformed Mg alloy was analyzed via an electron backscattered diffraction (EBSD) technique.
Abstract: Deformation and fracture behaviors of AZ31 and E-form Mg alloys sheets were investigated during Erichsen test. Formability of Mg alloys was discussed in terms of Erichsen index (IE) and tests were conducted at room temperature using conventional Erichsen tester. The role of difference in initial textures and grain sizes in Mg alloys sheets was investigated to understand the deformation and fracture mechanisms in Mg alloys during Erichsen test. The evolution of the microstructure and microtexture of the deformed Mg alloys was analyzed via an electron back-scattered diffraction (EBSD) technique. Crystal plasticity finite element method (CPFEM) was used to predict the micromechanical deformation behavior of Mg alloys during Erichsen test. EBSD analysis revealed that deformation twins along with shear localization by dislocation slip were the main deformation mechanisms during Erichsen test. E-form Mg alloys with a weaker basal texture show higher IE compared to AZ31 alloy with a stronger basal texture.
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27 Jun 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the heterogeneity of both deformation and twinning behaviors through the thickness direction in E-form Mg alloy sheets was investigated via conventional Erichsen testing at room temperature.
Abstract: The heterogeneity of both deformation and twinning behaviors through the thickness direction in E-form Mg alloy sheets was investigated via conventional Erichsen testing at room temperature (RT). The microtexture heterogeneity through the thickness direction of the E-form Mg alloy sheets deformed by different punch strokes (PSs) is discussed in terms of deformation twinning and de-twinning. The evolution of the microtexture, twin and KAM (kernel average misorientation) of E-form Mg alloy sheets deformed by different PSs was analyzed via electron back-scattered diffraction (EBSD) technique. A crystal plasticity finite element method (CPFEM) based on a random mapping (RM) scheme was used to simulate the heterogeneities of the strain/stress states of E-form Mg alloy sheets through the thickness direction during an Erichsen test. The evolution of the strain/stress that developed in E-form Mg alloy sheets during Erichsen testing was analyzed for different regions through the thickness direction under different PSs. EBSD analysis revealed that tension (TTWs), compression (CTWs) and double (DTWs) twins were the main deformation mechanisms in the upper portions. However, in the lower portions, a change in the sign of strain/stress components during Erichsen testing resulted in a significant formation of TTWs in the early stages and in a de-twinning of TTWs in the later stages.
20 citations
21 Aug 2020
TL;DR: In this paper, 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.
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 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.
5 citations
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TL;DR: In this paper, a combination of experimental and simulation techniques were used to investigate the plastic behavior of wrought magnesium alloy and found that an increased activity of non-basal dislocations provides a self-consistent explanation for the observed changes in the anisotropy with increasing temperature.
Abstract: Mechanistic explanations for the plastic behavior of a wrought magnesium alloy are developed using a combination of experimental and simulation techniques. Parameters affecting the practical sheet formability, such as strain hardening rate, strain rate sensitivity, the degree of anisotropy, and the stresses and strains at fracture, are examined systematically by conducting tensile tests of variously oriented samples at a range of temperatures (room temperature to 250 °C) and strain rates (10−5–0.1 s−1). Polycrystal plasticity simulations are used to model the observed anisotropy and texture evolution. Strong in-plane anisotropy observed at low temperatures is attributed to the initial texture and the greater than anticipated non-basal cross-slip of dislocations with 〈a〉 type Burgers vectors. The agreement between the measured and simulated anisotropy and texture is further validated by direct observations of the dislocation microstructures using transmission electron microscopy. The increase in the ductility with temperature is accompanied by a decrease in the flow stress, an increase in the strain rate sensitivity, and a decrease in the normal anisotropy. Polycrystal simulations indicate that an increased activity of non-basal, 〈c + a〉, dislocations provides a self-consistent explanation for the observed changes in the anisotropy with increasing temperature.
1,427 citations
25 Nov 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The extrusion behavior, texture and tensile ductility of five binary Mg-based alloys have been examined and compared to pure Mg in this article, and the five alloying additions examined were Al, Sn, Ca, La and Gd.
Abstract: The extrusion behaviour, texture and tensile ductility of five binary Mg-based alloys have been examined and compared to pure Mg. The five alloying additions examined were Al, Sn, Ca, La and Gd. When these alloys are compared at equivalent grain size, the La- and Gd-containing alloys show the best ductilities. This has been attributed to a weaker extrusion texture. These two alloying additions, La and Gd, were found to also produce a new texture peak with 〈 1 1 2 ¯ 1 〉 parallel to the extrusion direction. This “rare earth texture” component was found to be suppressed at high extrusion temperatures. It is proposed that the 〈 1 1 2 ¯ 1 〉 texture component arises from oriented nucleation at shear bands.
669 citations
TL;DR: In this article, a crystal-mechanics-based constitutive model was developed for polycrystalline hcp materials and evaluated for the room-temperature deformation of the magnesium alloy AZ31B.
Abstract: A crystal-mechanics-based constitutive model, which accounts for both slip and twinning, has been developed for polycrystalline hcp materials. The model has been implemented in a finite-element program. The constitutive model is evaluated for the room-temperature deformation of the magnesium alloy AZ31B. By using comparisons between model predictions and macroscopically-measured stress-strain curves and texture evolution, we have deduced information about the dominant slip and twinning systems active at room temperature, and the values of the single-crystal parameters associated with slip and twin system deformation resistances. Our calculations show that the two main crystallographic mechanisms: (i) slip on basal (0001) 〈11 2 0〉, prismatic {10 1 0} 〈11 2 0〉, and pyramidal {10 1 1} 〈11 2 0〉 systems, and (ii) twinning on pyramidal {10 1 2} 〈 1 011〉 systems, play the dominant role in the deformation of magnesium at room temperature. However, to match the observed stress-strain curves, it is found necessary to account for non-crystallographic grain boundary related effects. We approximately account for these grain-boundary region accommodation effects by adding a suitably-weighted isotropic term to the flow rule. The isotropic plasticity term serves the important function of bounding the stress levels in the numerical calculations; it does not contribute to the crystallographic texture evolution. Overall, we show that a simple non-hardening crystal-mechanics-based constitutive model is able to reproduce the experimentally-measured stress–strain curves and crystallographic texture evolution in simple tension and compression on specimens made from an initially-textured rod, as well as plane strain compression experiments on specimens made from an initially-textured plate.
537 citations
25 Oct 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, Mg-Ce alloy was hot-rolled and its mechanical properties were investigated by conducting tensile and Erichsen tests at room temperature and 433 K. This was attributed to a reduction in basal texture intensity and the splitting of the basal plane by the addition of a small amount of Ce.
Abstract: Mg–0.2 wt%(0.035 at.%)Ce alloy was hot-rolled and its mechanical properties were investigated by conducting tensile and Erichsen tests at room temperature and 433 K. The rolled Mg–Ce alloy exhibited greater elongation to failure and higher stretch formability than the rolled pure Mg. This was attributed to a reduction in basal texture intensity and the splitting of the basal plane by the addition of a small amount of Ce (0.2 wt%). Also, the small amount of Ce strongly affected the recrystallization behavior during hot rolling. Microstructural observation revealed that the prismatic slip was activated in the Mg–Ce alloy. The enhancement of the non-basal slip by the addition of Ce was not attributed to a reduction in the c/a ratio. An increase in stacking fault energy due to the addition of Ce is suggested to play a vital role in the activation of the non-basal slip.
229 citations
TL;DR: In this article, the tensile tests and the Erichsen tests at room temperature have been performed on seven kinds of Mg alloys: Mg-1.5Zn, Mg 1.5Mn alloys.
Abstract: The tensile tests and the Erichsen tests at room temperature have been performed on seven kinds of Mg alloys: Mg-1.5Zn, Mg-1.5Zn0.1Ca, Mg-3Zn, Mg-3Zn-0.1Ca, Mg-3Al, Mg-3Al-0.1Ca and Mg-1Al-1Zn-0.1Ca-0.5Mn alloys. In the Mg-Zn alloys, the 0.2% proof stress at 90 � , which was the angle between the tensile direction and the RD, was decreased by addition of Ca, while the 0.2% proof stress at 0 � was increased by addition of Ca. Also, an increase in elongation to failure by addition of Ca at 90 � was larger than that at 0 � . However, such variations in tensile properties by addition of Ca were not found in the Mg-Al alloy. The stretch formability for the Mg-Zn alloys was significantly enhanced by addition of Ca, while the stretch formability of the Mg-Al alloy was not enhanced by addition of Ca. These results by the mechanical testing are ascribed to the variations in basal texture by addition of Ca. [doi:10.2320/matertrans.M2011048]
164 citations