Investigations of microstructure, impact toughness, and fatigue failure behavior of bulk UFG Al-Li 8090 alloy processed by multi-axial forging

This study investigates the profound influence of multi-axial forging (MAF) on the microstructural characteristics, high cycle fatigue properties, and impact toughness behaviour of the bulk ultrafine-grained aluminum-lithium (Al-Li) 8090 alloy. The solution-treated Al-Li 8090 alloy was subjected to MAF at both liquid nitrogen temperature (LNT) and room temperature for 2, 4, and 6 forging cycles, resulting in cumulative true strains of 1.2, 2.4, and 3.6, respectively. The MAFed sample at LNT after 6 cycles displayed a well-defined ultrafine-grained microstructure, exhibiting grain sizes ranging from 100 to 400 nm. Detailed electron backscatter diffraction analysis confirmed significant grain refinement with increasing MAF cycles for various conditions. The high-cycle fatigue strength exhibited a progressive enhancement with the increasing number of cycles and was observed to be maximum for the CF cycle-6 condition (131 MPa), attributing to the effective suppression of dynamic recovery at cryogenic temperatures.