Influence of grain size and stacking-fault energy on deformation twinning in fcc metals

Abstract

This article investigates the microstructural variables influencing the stress required to produce deformation twins in polycrystalline fcc metals. Classical studies on fcc single crystals have concluded that the deformation-twinning stress has a parabolic dependence on the stacking-fault energy (SFE) of the metal. In this article, new data are presented, indicating that the SFE has only an indirect effect on the twinning stress. The results show that the dislocation density and the homogeneous slip length are the most relevant microstructural variables that directly influence the twinning stress in the polycrystal. A new criterion for the initiation of deformation twinning in polycrystalline fcc metals at low homologous temperatures has been proposed as ( tw Ϫ 0 )/G ϭ C(d/b) A , where tw is the deformation twinning stress, 0 is the initial yield strength, G is the shear modulus, d is the average homogeneous slip length, b is the magnitude of the Burger's vector, and C and A are constants determined to have values of 0.0004 and Ϫ0.89, respectively. The role of the SFE was observed to be critical in building the necessary dislocation density while maintaining relatively large homogeneous slip lengths.

Modeling the deformation behavior of Hadfield steel single and polycrystals due to twinning and slip

“…Then, the strain hardening changes with the reciprocal of the mfp of dislocations. Experimental work by ElDanaf et al [13] indicates an inverse dependence of the dislocation density evolution on the mfp (homogeneous deformation zone size) consistent with the model adopted in the present work.…”

“…materials is the lack of a physical basis for the relation between the length scale (i.e. grain size or homogeneous deformation zone [13]) and the dislocation density evolution [14]. The hardening associated with the evolution of dislocation density is represented with a statistical storage term (athermal component) proportional to the square root of dislocation density and a dynamic recovery term proposed by Mecking and Kocks [15], leading to a well-known Voce type hardening law.…”

Crystallographically degenerate B2 precipitation in a plastically deformed fcc-based complex concentrated alloy

“…The latter observation suggests that the secondary twins have been intersected by other deformation entities (e.g. dislocations, fine-scale tertiary twins) during the cold-rolling process [18,19]. A careful examination of the secondary twins (dotted rectangle in Figure 4(d)) also implies that they have emanated from a wider variant (#1).…”

Ductility Sensitivity to Stacking Fault Energy and Grain Size in Cu–Al Alloys

“…[19][20][21] In contrast, fully recrystallized twinning-induced plasticity steels and Cu-Al alloys with grain sizes smaller than 1 μm have been fabricated by cold rolling and annealing process, [18,22,23] which makes it feasible to study the ductility and deformation mechanisms from the finegrained regime to the coarse-grained regime.…”

“…[12,13,18,20,26,28] After characterizing the microstructures after tensile tests, the deformation patterns of the Cu-Al alloys with different SFEs and grain sizes were summarized and schematically shown in Figure 2. When the SFE is higher than 30 mJ/m 2 , only dislocation configurations were detected during tensile test in this study when the grain size is larger than about 1 μm.…”