Revealing the role of heterostructural parameters in hetero-deformation induced stress of Mg-13Gd alloy

Heterostructured materials as a new class of materials have excellent mechanical properties due to heterodeformation induced (HDI) strengthening and hardening. However, how do heterostructural parameters affect the evolution of geometrically necessary dislocations (GNDs) and HDI stress remains unclear. In this paper, heterostructured Mg-13Gd (wt.%) alloy was prepared by pre-aging and different extrusion temperature under small extrusion ratio, which fabricates various heterostructural parameters (including grain size, texture, precipitates, Gd solute atoms and misorientation). With increasing extrusion temperature, these heterostructural parameters gradually disappear. Heterogeneous texture between coarse and fine grains leads to their variation difference of GNDs density. Meanwhile, the accumulation of GNDs is more serious at the domain boundaries in coarse grains due to larger dislocation storage space. Compared with the homogeneous sample, the segregation behavior of Gd solute atoms and the chain-like precipitates at domain boundaries as well as sub-grain boundaries in coarse grains of heterogeneous sample are found more effective in developing GNDs pile-up, leading to higher HDI stress. These findings contribute to the design of heterostructured materials to optimize HDI strengthening and hardening.