The Role of Texture, Temperature and Strain Rate in the Activity of Deformation Twinning

Abstract

Plastic deformation in cubic metals is relatively simple due to the high crystallographic symmetry of the underlying structure. Typically, one unique slip mode can provide arbitrary deformation. This is not true in lower symmetry hexagonal metals, where prismatic and basal slip (the usual favored modes) are insufficient to provide arbitrary deformation. Often, either pyramidal slip and/or deformation twinning must be activated to accommodate imposed plastic deformation. The varied difficulty of activating each of these deformation mechanisms results in a highly anisotropic yield surface and subsequent mechanical properties. Further, the relative activity of each deformation mode may be manipulated through control of the initial crystallographic texture, opening new opportunities for the optimization of mechanical properties for a given application.

Kinking Nonlinear Elasticity and the Deformation of Magnesium

“…[11,32] The same is true of highly oriented microstructures loaded parallel to their basal planes. [19,20,24,27,28,33] In contradistinction to the large anisotropies observed when highly oriented microstructures are loaded parallel to their basal planes, [19,20,24,27,28,33] in cast Mg alloys with random texture, the differences between the stressstrain curves obtained in compression or tension are small. [13][14][15] Along the same lines, Mg and its alloys are characterized by high damping and the related phenomenon of pseudoelasticity.…”

“…The plateau has been associated with the twinning of easy-to-twin grains, which initially results in softening. [27,33] Such twins presumably rotate grains such that their basal planes are in a better position to form IKBs, which, in turn, increases W d . As more twins form, they presumably result in the work hardening observed at the end of the plateau, which, in turn, results in a reduction in the domain size which increases the threshold stress and thus decreases W d .…”

“…[27,28,69] The response of Ti 3 SiC 2 at room temperature is fully reversible until failure, i.e., there is no plastic deformation. Plastic deformation is only observed at temperatures higher than the brittle-toplastic transition, at which point the fracture toughness drops, but the strain to failure, due to cavitation and microcracking, is greatly enhanced.…”

Effects of Temperature and Strain Rate on the High-Temperature Workability of Strip-Cast Mg-3Al-1Zn Alloy

“…[11] These twin formations are also related to the initial texture formation of as-received materials. [12] If the strong basal texture is formed in conventionally rolled sheet, ''twinning anisotropy'' is usually reported to occur. [13] If the compressive axis of the specimen is parallel to the normal direction (ND) of conventionally rolled sheet, most basal planes are in the state of the condition of c-axis compression.…”

Simulation of strain-softening behaviors in an AZ31 Mg alloy showing distinct twin-induced reorientation before a peak stress

“…However, their low workability using conventional processing conditions limits broader application [10]. Although strain-hardening behaviors of Mg and its alloys have been studied extensively [12][13][14][15][16][17][18][19][20][21][22][23][24], strain-softening behaviors are less understood. Most studies have focused on identifying mechanisms of DRX during elevated temperature deformation.…”