Effects of extrusion temperature on microstructure evolution and mechanical properties of heterogeneous Mg-Gd alloy laminates via accumulated extrusion bonding
(1. State Key Laboratory of Mechanical Transmission, College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China)
2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China)
Abstract: The influence of extrusion temperature on microstructure and mechanical properties of heterogeneous Mg-1Gd/Mg-13Gd laminate prepared by accumulated extrusion bonding was investigated. The results reveal that the Mg-1Gd/Mg-13Gd laminate forms a significant difference in grain size between the successive layers when extruded at 330 °C, and this difference gradually disappears as the extrusion temperature increases from 380 to 430 °C. Besides, the growth rate of recrystallized grains in fine-grained layers is faster than that in coarse-grained layers. Moreover, the diffusion ability of Gd element increases with elevating extrusion temperatures, promoting the increase and coarsening of precipitates in fine-grained layers. Tensile tests indicate that the sample extruded at 380 °C has a superior combination of strength and ductility. This is mainly attributed to the synergy of the heterogeneous texture between coarse and fine-grained layers, hetero-deformation induced strengthening and hardening. The fine-grained layers facilitate the activation of prismatic áa？ slips, while coarse-grained layers make it easier to active basal áa？ and pyramidal ác+a？ slips, especially for the sample extruded at 380 °C. The activation of pyramidal ác+a？ slips contributes to coordinating further plastic deformation.
Key words: Mg-Gd alloys; heterogeneous structure; texture; mechanical properties; slip modes