Effect of texture on elastic precursor decay in magnesium alloy AZ31B.

The role of texture in the dynamic yielding behaviour of magnesium alloy AZ31B has been studied in a series of instrumented plate-impact experiments. Specimens with thicknesses between 0.45 and 2 mm were cut parallel and perpendicular to the material extrusion direction and shock loaded to impact stresses around 3 GPa. Frequency-shifted photon doppler velocimetry was performed to capture breakout of the weak shockwave at the rear free-surface. Significant decay of the elastic precursor wave is observed over the examined thickness range. It is shown that shock compression along the extrusion direction (longitudinal loading) exhibits a markedly higher Hugoniot elastic limit (HEL) when compared to the perpendicular direction (transverse loading). Microstructural analysis via Electron Backscatter Diffraction (EBSD) demonstrates a strong basal texture in the material, with the c-axes of the HCP lattice aligned perpendicular to the extrusion direction. It is indicated that the peak elastic stress can be linked to the distribution of angles between the loading direction and the c- and a-axes of the grains, and by extension to the Schmid factors in the three primary slip systems. The present results demonstrate the importance of texture in the time-dependent inelastic deformation of common alloys with highly anisotropic crystal structures such as Mg AZ31B. [ABSTRACT FROM AUTHOR]