EBSD Observation for Reversible Behavior of Deformation Twins in AZ31B Magnesium Alloy
01 Aug 2009-Materials Transactions (The Japan Institute of Metals and Materials)-Vol. 50, Iss: 8, pp 2118-2120
TL;DR: A bending device used for SEM-EBSD systems has been developed by as mentioned in this paper, which enables one to intermittently observe changes in microstructures induced by deformation in the same viewing area.
Abstract: A bending device used for SEM-EBSD systems has been developed by the authors, which enables one to intermittently observe changes in microstructures induced by deformation in the same viewing area. Alternate compression-tension loading was applied to a sheet specimen of AZ31B magnesium alloy by bending the specimen. Twins were formed by compression straining. They remained after un-loading. Applying tensile straining lead to the disappearance of all the twins. Most of twins were those of {10\\bar12} types. Anisotropy in mechanical properties of magnesium alloys would be affected by this twinning and de-twinning behaviors.
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TL;DR: In this article, the deformation dynamics and the effect of deformation history on plastic deformation in a wrought magnesium alloy were investigated using real-time in-situ neutron diffraction measurements under a continuous-loading condition and elastic-viscoplastic selfconsistent (EVPSC) polycrystal modeling.
75 citations
15 Aug 2012-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors present the work-hardening behaviors of a rolled AZ31B magnesium alloy sheet during in-plane cyclic loading, and the overall trend of the stress-strain curve was as follows.
Abstract: This paper presents the work-hardening behaviors of a rolled AZ31B magnesium alloy sheet during in-plane cyclic loading. The overall trend of the stress–strain curve was as follows. As established before, the yield stress under compression was considerably less than that under tension, and an inflected shape was observed in the stress–strain curve during the subsequent tension. Furthermore, an asymmetric evolution of work-hardening was observed as follows. The rate of work-hardening in the late stage of compression became gradually large with an increase in the number of cycles. Owing to this increase in the rate of work-hardening, the stress at the end of compression increased as the number of cycles increased. On the other hand, the rate of work-hardening in the late stage of tension became small as the number of cycles increased, yielding a decrease in the stress at the end of tension with the increase in the number of cycles. The results were almost the same when the cyclic loading test was carried out after tensile strain was applied to the sheet. On the other hand, when the cyclic loading test was carried out after compressive strain was applied, the increase in the rate of work-hardening in the late stage of compression was significantly more pronounced, whereas the inflected shape of the curve during tension was considerably less pronounced. The mechanisms of the above macroscopic behaviors were investigated in terms of twinning.
62 citations
TL;DR: In this paper, an extruded ZK60 magnesium alloy was subjected to fully-reversed strain-controlled cyclic loading at a strain amplitude of 4.0% in the extrusion direction in ambient air.
41 citations
TL;DR: In this article, the damping capacity of extruded pure magnesium was examined to understand the role played by preexisting twins introduced by pre-strain, which was characterized by bending vibration decay.
38 citations
01 Jan 2012
TL;DR: In this paper, an overview of twinning in magnesium base alloys with a focus on recent advances made using new techniques such as electron backscattering diffraction, advanced phenomenological models and atomistic modelling is presented.
Abstract: :
In magnesium and its alloys, twinning plays a critical role in determining many characteristics of the mechanical response. The present chapter provides an overview of twinning in magnesium base alloys with a focus on recent advances made using new techniques such as electron backscattering diffraction, advanced phenomenological models and atomistic modelling. The present chapter is organized to first present the reader with a picture of the fundamental features of twinning. Next, the manner in which twinning affects the mechanical response is examined. Finally, the scope to manipulate twinning with the metallurgical ‘tools’ of alloying and processing is considered.
32 citations
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TL;DR: In this article, the authors present room-temperature deformation mechanisms in polycrystalline Mg alloys and show that dislocation slip of basal and prismatic alloys can occur nearly at the same ease when the basal planes are tilted in such a way that the Schmid-factor ratio (equivalent to the critically resolved shear stress (CRSS) ratio) of prismatic to basal slip is larger than a value ranging from 1.5 to 2.
Abstract: This article presents room-temperature deformation mechanisms in polycrystalline Mg alloys. Dislocation slip of basal 〈a〉 and prismatic 〈a〉 types are shown to occur nearly at the same ease when the basal planes are tilted in such a way that the Schmid-factor ratio (equivalent to the critically resolved shear stress (CRSS) ratio) of prismatic 〈a〉 to basal 〈a〉 slip is larger than a value ranging from 1.5 to 2.0, depending on the initial texture distribution and grain size. Grain-boundary sliding (GBS) also occurs at room temperature up to 8 pct of total strain, enhanced by plastic anisotropy as well as by the increasing number of grain-boundary dislocations. Twinning plays an important role in both flow and fracture behaviors. Twins are induced mostly by stress concentrations caused by the anisotropic nature of dislocation slip. Twins can be classified into two types based on their shape: a wide lenticular type and a narrow banded type. The wide twins are
$$\{ 10\bar 12\} $$
twins appearing in the early stage of deformation and accompany little change of surface height. The narrow twins are
$$\{ 10\bar 11\} $$
or
$$\{ 30\bar 32\} $$
appearing in the late stage of deformation and accompany a substantial change in surface height. The formation of the narrow twins seems to give rise to highly localized shear deformation within the twin, leading to strain incompatibility and to final failure.
610 citations
TL;DR: In this paper, large stress-strain hysteresis loops are observed in sand-cast material in a variety of tempers under tension or compression, and in high-pressure diecast material with different cross-section thickness tested in tension.
245 citations
TL;DR: In this article, the effects of the mechanical anisotropy on the fatigue behavior and deformed microstructure of a commercially extruded Mg-Al-Zn alloy having an average grain size of about 15 mm were investigated.
Abstract: Tensile, compression and fatigue tests were carried out on a commercially extruded Mg-Al-Zn alloy having an average grain size of about 15 mm. The tensile and compression tests at room temperature showed that the yield strength in tension was much higher than that in compression. The lower yield strength in compression resulted from its texture. The effects of the mechanical anisotropy on the fatigue behavior and its deformed microstructure were also investigated under a stress ratio of R ¼ 0:1 and � 1. The fatigue strength, stress amplitude, at N ¼ 10 7 cycles under R ¼� 1 and 0.1 was about 120 and 90 MPa, respectively. The mechanical properties and the deformed microstructure observations indicated that the formation of deformation twins was related to the between maximum stress and the yield strength in tension and compression: the deformation twins were formed in the sample (maximum stress is higher than the yield strength) and showed no deformation twins in the sample (maximum stress is lower than the yield strength). [doi:10.2320/matertrans.MRP2007292]
21 citations