Analysis for twinning and slip in face-centered cubic crystals under axisymmetric co-deformation

Abstract

The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals (f.c.c.) for twinning on {111} 112 and slip on {111} 110 systems. The influence of ξ , the ratio of critical resolved shear stress for twinning to slip, on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically. The Taylor factors and the anisotropy of yield strength for three important orientations [100], [110] and [111] in orientation space were analyzed. It is found that the yield strength asymmetry for the case of axisymmetric deformation of tension and compression can be explained based on the microscopic theory of crystal plasticity. The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation. The deformation texture formation and development of f.c.c. crystals with low stacking fault energy for axisymmetric tension can be explained qualitatively on the basis of analyzed results.

Achieving strong and stable nanocrystalline Al alloys through compositional design

“…The Al-Fe alloy has a strong out-of-plane (111) texture and the nanograins experienced in-plane rotation; hence, the texture along Si[2 11 ], the in-plane test direction, is either polycrystalline or approximates to < 112 > . In either ca se, the Taylor factor along the in-plane direction is proximately equal to 3.06 [125,126]. The ratio of two Taylor factors is 1.2, in accordance with the experimentally measured 1.25, suggestive of a texture-determined anisotropy under the compression mode.…”

“…Taylor factor is intimately associated with the SFE as well as the ratio, ξ, of critical resolved shear stresses for twinning and slips for FCC metals. Taylor factors were estimated using criterion of maximum work principle of Bishop-Hill [123,124] and were well depicted by Chen et al [125] For Al and its alloys with ultrahigh SFE, ξ is greater than 2/ √ 3 and the Taylor factor for [111] direction is ~ 3.67. The Al-Fe alloy has a strong out-of-plane (111) texture and the nanograins experienced in-plane rotation; hence, the texture along Si[2 11 ], the in-plane test direction, is either polycrystalline or approximates to < 112 > .…”