Microstructural evolution and mechanical properties of 2195 Al-Li alloy processed by rapid solidification and thermo-mechanical processing

Abstract

2195 Al-Li alloy billet was prepared by gas atomization (GA) and hot isostatic pressing (HIP), followed by hot extrusion and different heat treatments. Microstructural evolution and mechanical properties of the alloy were investigated. The results show that the HIPed alloy presents a fine microstructure, but with clear powder boundaries and Mg element segregation. Hot extrusion breaks the powder boundary and eliminates the element segregation, thus improving the mechanical properties of the alloy. After solution and aging treatments, a large number of T1 and θ' phases are precipitated, and the alloy strength is significantly improved. The introduction of pre-deformation before artificial aging produces a high density of fine T1 phase and suppresses the formation of the σ phase. The T8 specimen exhibits an excellent mechanical property with the ultimate tensile strength of 600 MPa, yield strength of 576 MPa, and elongation of 9%. The improved ductility is ascribed to the narrow precipitate free zone, the discontinuous and small grain boundary phase, and the moderate enrichment of the T1 phase at the sub-grain boundaries in the alloy.