Hot Deformation Characteristics and Dynamic Recrystallization Mechanisms of a Semi-Solid Forged AZ91D Magnesium Alloy

Abstract

Magnesium alloys show great promise in high-speed transport, aerospace, and military technology; however, their widespread adoption encounters challenges attributed to limitations such as poor plasticity and strength. This study examines the high-temperature deformation of semi-solid forged AZ91D magnesium alloy through a combination of experiments and simulations, with a focus on comprehending the influence of deformation conditions on dynamic recrystallization (DRX). The findings disclose that conspicuous signs of DRX manifest in the yield stress curve as strain increases. Additionally, decreasing the strain rate and temperature correlates with a reduction in both yield stress and peak strain, and the activation energy is 156.814 kJ/mol, while the critical strain and peak strain remain relatively consistent (εc=0.66208εp). Microstructural changes during high-temperature deformation and the onset of DRX are thoroughly examined through experimental methods. Moreover, a critical strain model for DRX and a predictive model for the volume fraction of DRX were formulated. These equations and models, validated through a combination of experiments and simulations, serve as invaluable tools for predicting the mechanical behavior and microstructural evolution, which also establishes a foundation for accurately predicting the deformation behavior of this alloy. By analyzing the hot deformation characteristics and dynamic compression mechanism of the newly developed semi-solid forging AZ91D magnesium alloy, a numerical simulation model can be effectively established. This model objectively reflects the changes and distributions of stress, strain, and rheological velocity, providing a scientific basis for selecting subsequent plastic deformation process parameters and designing mold structures.