Analyses on Compression Twins in Magnesium

Abstract

The orientation relationships between the compression twins and their matrices in magnesium were investigated using EBSD technique. Schmid factor analyses were applied to determine the orientation dependency of compression twins and the condition for double twinning. Results show that thin compression twin bands of f10 1 11g type lose easily their exact twin relation of 56 h11 2 20i to $40 h11 2 20i due to the instability of twin orientation and immobility of twin boundaries. And the basal orientation with TD-rotation tends to induce tension twinning in compression twins.

Orientational analysis of static recrystallization at compression twins in a magnesium alloy AZ31

“…Because of this, it is necessary to describe how static recrystallization in magnesium proceeds without the change of deformation texture which was often observed during both dynamic and static recrystallization. The present study extends our previous investigations of the orientations of compression twins/shear bands and the morphological difference between the two types of twins and their Schmid factor distributions [32,33]. In this work, we further inspect the nucleation and texture evolution of static recrystallization by means of SEM, EBSD, and X-ray diffraction analyses.…”

“…In the condition of plane strain compression, the Schmid factors of 6 twin variants 3 located in the same semicircle of the (0002) pole figure as matrix A should form more easily than the variants 5 and 6 in the other semicircle. However, the orientations of 2 and 3 are rather unstable and should rotate either through basal slip toward B or through tension twinning toward the center region C (for a detailed and quantitative analysis, see [33]). In addition, the formation of twin variants 5 and 6, or of double twins, establishes an accommodation within grains under external stress/strain.…”

“…At a higher temperature, the shear bands developed from compression twins are much wider and better evolved and thus may be detected with X-ray diffraction. In our previous work [32,33], we analyzed the orientation changes in compression twins using the EBSD technique. Here, we give only a brief summary of these previous works.…”

Tailoring Microstructure and Properties of Fine Grained Magnesium Alloys by Severe Plastic Deformation

“…These twins nucleate in a lenticular shape and then grow in thickness tending to occupy the entire grain eventually . Another type of twinning, which is associated with contraction along the c ‐axis (“contraction twins”), occurs in Mg alloys on plane . With increasing strain, such twins usually grow in number density rather than in size.…”

Slip dislocation and twin nucleation mechanisms in hcp metals

“…25% strain at room temperature [2], and under low compression at high temperature, above 400 o C [3].In magnesium and its alloys{10 11} twins are less frequent than tensile{10 12} twins. However, they were observed, for instance, in AZ31 alloy under uniaxial compression of samples with basal texture [4].…”