Sequencing the Twinning-Detwinning Microstructural Footprint from Normal, Oblique, Converging, and Diverging Rarefaction Waves in AZ31B-H24 Magnesium at the Extremes

Materials under extreme dynamic loading such as in ballistic and planetary impacts undergo elevated pressures, temperatures, and strain rates. It is well known that extreme dynamic loading can lead to profound changes in microstructure, microstructure evolution, and consequently residual mechanical properties. Experimental techniques for ascertaining the macroscopic response of materials to shock loading are well established, but insight into fundamental mechanisms of deformation requires the ability to characterize the microstructure and its evolution in real-time (in-situ) and post-mortem (ex-situ). Majority of plate impact shock experiments utilize planar free surfaces to study microstructure evolution in condensed matter. For this research, we seek to study the twinning-detwinning behavior of AZ31B-H24 magnesium alloy via shock recovery experiments using flyers with planar, concave, convex, and oblique free surfaces. These experiments will guide in understanding the role of the shear component of the rarefaction wave at the fundamental level. Samples were shock compressed to approximately 0.8 GPa and 1.7 GPa respectively along the plate normal, transverse, rolling, and off-axis directions, then released back to ambient conditions. The as-received and residual microstructures were characterized and sequenced to understand the role of shear waves on the evolution of crystallographic texture. The acquired results will provide insight into the complex twinning-detwinning behavior of this AZ31B-H24 magnesium alloy under shock compression and release.