Work-hardening behaviors of magnesium alloy sheet during in-plane cyclic loading

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.

Anisotropic deformation behavior under various strain paths in commercially pure titanium Grade 1 and Grade 2 sheets

“…These authors reported that the cyclic hardening/softening behavior varied as the strain amplitudes and cycles changed. Similar results [20][21][22][23] were observed for Mg alloys, which have the same hcp crystal structure as Ti. Plane-strain compression tests were performed by Ayman et al [14].…”

“…This mechanism may be explained in terms of an analogy with Mg alloy sheets as follows. It was reported that in a Mg alloy sheet, a retardation of the beginning of the second rapid increase in work-hardening, i.e., the expansion of plateau region, was observed during compression in cyclic loading [21,35]. This work-hardening behavior occurred for the following reason.…”

“…To prevent buckling during in-plane compression of the sheets, comb-shaped dies were utilized to apply compressive forces through the thickness. The experimental apparatus and comb-shaped dies were the same as those used in our previous works [9,21]. A compressive stress of 3.6 MPa was applied to the thickness direction of the sample.…”

“…The stress-strain curves of Mg alloy sheets are significantly different between tension and compression [21,31,[40][41][42]. Moreover, a sigmoidal curve occurs when a Mg alloy sheet is subjected to compression followed by tension, whereas this curve does not occur under tension followed by compression [20,21,41].…”

“…Moreover, a sigmoidal curve occurs when a Mg alloy sheet is subjected to compression followed by tension, whereas this curve does not occur under tension followed by compression [20,21,41].…”