Superplastic deformation behavior of fine-grained AZ80 magnesium alloy prepared by friction stir processing

Abstract

Friction stir processing (FSP) is a new severe plastic deformation technique where microstructure refinement, homogenization, and densification occur simultaneously. In this study, the microstructure and superplastic deformation behavior of AZ80 magnesium alloy prepared by FSP were investigated. FSP led to remarkable grain refinement and modification of texture for AZ80 magnesium alloy. A maximum elongation of 606% was obtained at 3 × 10−4 s−1 and 350 ℃. When superplastic deformation was conducted at 3 × 10-3 s−1 and 300 ℃, or at 1 × 10-4 s−1 and 400 ℃, the superplasticity was relatively lower, thus exhibiting a lower strain rate sensitivity. The coarsening of both grains and β-Mg17Al12 precipitates deteriorated superplastic elongation. Applied deformation promoted the premature dissolution of β precipitates at 400 ℃ during superplastic deformation. Moreover, superplastic deformation weakened and spread the basal texture. Although the activation of prismatic and pyramidal slips is beneficial for superplastic deformation, grain boundary sliding is the main superplastic deformation mechanism.

Keywords

• Friction stir processing
• Magnesium alloy
• Microstructure
• Superplasticity
• Grain refinement