This DoD project investigates and characterizes the microstructural evolution of magnesium and magnesium alloys under high temperatures and severe plastic deformation. Electron backscatter detection, X-ray diffraction, and conventional microscopy are being used together with serial sectioning to study the microstructure of magnesium following thermo-mechanical processing.
Interest is being shown in Mg due to its light weight and high potential strength. However, traditional mechanical processing is difficult due to Mg’s anisotropic material properties. A severe plastic deformation (SPD) method called Equal Channel Angular Extrusion (ECAE) has had good results with Mg above approximately 0.5 homologous temperature. This project investigates the effects temperature, strain-rate, and processing route on the microstructural evolution of Mg and an aluminum containing Mg alloy called AZ31 following ECAE processing. Electron backscatter detection, X-ray diffraction, and microscopy are used to characterize the microstructures. In addition, a serial sectioning system using femtosecond laser ablation is being developed which will be used to construct a 3-D model of Mg.
Of particular interest in the thermo-mechanical processing of Mg is a recovery-like process called dynamic recrystallization (DRX). During DRX, new grains nucleate and grow, generally resulting in grains with fewer dislocations than the parent grains and a change in texture. DRX occurs readily in Mg at many of the temperatures and strain-rates used in ECAE and is a significant factor in the resultant mechanical properties, but the process and mechanisms involved are poorly understood. To remedy this, in-situ diffraction experiments will be performed during ECAE to provide insight into orientation evolution and grain growth during DRX.