Effects of initial texture on the three-dimensional creep anisotropic behaviors of dilute Mg–Y binary alloy sheets

Abstract

The effects of initial texture on the three-dimensional creep anisotropic behaviors of dilute Mg–2Y(wt%) binary alloys were investigated in this study. Two kinds of sheets were used: one had a concentrated texture (CT sample) and the other had a split texture (ST sample). According to the compressive directions and conventional orthogonal coordinate system for sheet, the samples were named as CT-RD, CT-TD, CT-ND and ST-RD, ST-TD, ST-ND. Compressive creep tests were conducted at 493 K and applied stresses ranged from 40 to 100 MPa. The results showed that both CT and ST samples had evident three-dimensional creep anisotropy. Specifically, the creep resistance was highest in CT-ND sample, followed by ST-ND, ST-TD, CT-TD, CT-RD samples, and lowest in ST-RD sample. Next, the dominant creep mechanisms in all samples were strictly investigated using various characterization methods. For CT-RD and CT-TD samples, the dominant creep mechanisms were similar, including cross-slip and twinning. For CT-ND sample, the dominant creep mechanisms were dislocation climb and pyramidal <c+a> slip. For ST samples, a variety of creep mechanisms were detected, ranging from heavy basal slip to easy activations of cross-slip and twinning. A little bit dislocation climb and pyramidal <c+a> slip acted as plastic accompanying roles in ST samples. Furthermore, the variation of initial texture types led to the variations of dominant creep mechanisms and the different three-dimensional creep anisotropic behaviors. The rank of deteriorating creep resistance was revealed as basal slip > cross-slip > twinning > dislocation climb > pyramidal slip. Finally, it is proposed that future work on the enhancement of creep resistance of Mg alloys with rare earth addition should focus on the inhibition of basal slip and cross-slip.