Synergistic improvement in strength and plasticity of cold-drawn MP159 alloy via {111} gradient texture

The mechanisms underlying the simultaneous enhancement of yield strength and elongation in a cold-drawn MP159 alloy were investigated. Interrupted tensile tests, routine and in-situ electron backscatter diffraction (EBSD) were carried out to study the deformation behavior of MP159 alloy. The results reveal that the {111} gradient texture (GT) forms at the cross section of the cold-drawn sample, which can effectively enhance the strength-plasticity combination. The mechanical properties were enhanced via two synergistic mechanisms: (i) the self-equilibrium effect arising from the back stress induced by strain partitioning between the soft and hard regions, and (ii) the accumulation of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) at inter-region boundaries. With respect to plasticity, the stress drop rate after necking is decreased by {111} GT. In this way, the plasticity is further improved via the residual work-hardening capability in hard regions. Furthermore, the high yield strength of MP159 alloy is attributed to a combination of substructures, texture, and {111} GT.