Spall response and failure mechanisms associated with a hot-extruded AMX602 Mg alloy

Normal plate impact experiments were conducted to study the spall behavior of AMX602 magnesium alloy fabricated via Spinning Water Atomization Process (SWAP), which was followed by cold compaction and hot extrusion. Incipient spall damage in the specimens was measured at different shock conditions using 51 mm and 105 mm diameter bore gas guns. The Hugoniot Elastic Limit (HEL) was measured to be approximately 187 ± 11 MPa. The spall strengths extracted from the free surface velocity profiles of the shocked specimens was found to increase by 8% for shock stresses ranging from 1.61 to 4.53 GPa. The experimental data also revealed some inherent scatter in the spall strength data due to microstructural heterogeneity. Post-test fractographic analysis of the shock-recovered specimens suggests that the initiation of spall was most likely associated with intermetallic Al2Ca-bearing precipitates forming during the hot extrusion process. The subsequent spall failure propagated via cavitation events that involved the nucleation of nano- and micrometer-sized voids with very limited plastic growth.