Hot tensile deformation behavior of extruded LAZ532 alloy with heterostructure

Abstract

Hot tensile test was performed at deformation conditions of 150–°C300 °C and 8.33 × 10−5 s−1~1.67 × 10−3 s−1, respectively, to systematically study the microstructure development and deformation mechanism of extruded Mg–5Li–3Al–2Zn (LAZ532) alloy with a heterostructure of both the fibrous extrusion zones (FEZs) and non-fibrous extrusion zones (non-FEZs) coexisted. The results showed that the peak stresses decreased gradually, while the fracture strains increased gradually with the decrease of strain rates or the increase of deformation temperatures, and the alloy exhibited superplastic characteristics at deformation conditions of 300 °C and 8.33 × 10−5 s−1~1.67 × 10−3 s−1. By microstructure observation, the alloy showed that in the initial deformation stage, the deformation of the grains in the FEZs was prior to that in the non-FEZs. In the middle deformation stage, the deformation of the grains in the FEZs was dominated by intragranular slip and accompanied with grain boundary slip (GBS), while the deformation of the grains in the non-FEZs was dominated by GBS and accompanied with intragranular slip. In the later deformation stage, the continuous dynamic recrystallization (CDRX) generated in the coarse lamellar grains in the FEZs due to dislocation pile-up, in contrast, the discontinuous dynamic recrystallization (DDRX) generated at the grain boundaries in the non-FEZs. Moreover, based on theoretical calculation and result analysis, the activation energy was about 110.0 kJ/mol, and the hot tensile deformation mechanism was each other alternating and coordinated deformation mechanism among GBS, intragranular slip and dynamic recrystallization (DRX).