Loading Orientation Dependence of the Formation Behavior of Deformation Kink Bands in the Mg-Based Long-Period Stacking Ordered (LPSO) Phase

Abstract

The variation in the deformation behavior of a directionally solidified (DS) Mg-based long-period stacking ordered (LPSO)-phase crystal depending on the loading orientation was examined. The frequency of formation of the beak-like shape of the deformation band, which is known as one of the important deformation mechanisms in the LPSO phase, monotonically decreased as the inclination angle of the loading orientation with respect to the crystal growth direction in the DS crystal increased, and was accompanied by a decrease in the yield stress due to the activation of basal slip. Deformation bands formed along a direction approximately perpendicular to the grain boundary independent of the loading orientation. The crystal rotation axes selected in the deformation bands were perpendicular to [0001] in almost all grains, independent of the loading orientation. However, the rotation axes in the bands were not fixed but varied between h10 10i and h11 20i; this variation was correlated with the loading axis. These observed features strongly suggest that the deformation bands formed in the LPSO phase are predominantly deformation kink bands and that the formation mechanism itself does not vary with the loading orientation but instead its details. The selectivity of the crystal rotation axis in the kink band is strongly affected by the loading orientation.

Kinking in LPSO Mg-Zn-Y Alloys and Other Layered Materials

“…As it was noted in Ref. [40] kink bands develop macroscopically along a direction approximately perpendicular to grain boundary independent of the loading direction, and basal slip is increased with an increase in the orientation angle (Fig. 21).…”

“…In some works, these types are distinguished as kink band, ortho-and ridge kinks [37]. Other works distinguish pre-kink, kink [38], high-angle boundaries [39], and beak-like structures [40]. Despite such a large number of different names for deformation structures, many of them are similar in meaning.…”

“…An experimental illustration of the formation of large ridge kinks up to 600 μm was given in Ref. [40], where the effect of load orientation on the microstructure behavior of polycrystalline rectangular specimens is examined. Six different loading axes were chosen.…”

Two-Directional Micro-Laue Diffraction Mapping to Observe Kink Deformation in Long-Period Stacking-Ordered Mg–Zn–Y Alloys under Compression

“…14) We think the grain that deformed first might have a slightly bigger tilt angle from the h11 20i direction than that of the other grains. 11) As mentioned above, the change in sample height with sample load can be analyzed by using Figs. 3 and 4.…”