Effect of the structure and the phase composition on the mechanical properties of Al–Cu–Li alloy laser welds

Abstract

Abstract The purpose of these investigations was to study the effect of heat treatment on the structure and the phase composition of laser welded joints of the Al-2.8Cu-1.7Li alloy (V-1461 grade), providing the maximum tensile strength. To study the phase composition of the weld metal, synchrotron radiation was applied using a ‘Mega Science’ facility. This enabled to assess the phase distribution across the weld metal before and after heat treatment. It was found using high-resolution scanning and transmission electron microscopy, energy dispersive X-ray analysis, and synchrotron X-ray diffractometry that the T1(Al2CuLi) and T2(Al6CuLi3) main phases had been formed in the weld metal and at the interfaces with the matrix. Ultimate tensile strength of the welded joints was about 341 MPa, which was 62% of that of the base metal. Subsequent heat treatment of the welded samples, included hardening and artificial aging, caused the homogenization of the Al–Cu–Li alloy solid solution, as well as the formation of the δ′(Al3Li) hardening phase. Also, the T1 and T2 phases were formed partially. After quenching, tensile strength of the welded joints improved and was about 85% of that of the base metal. After artificial aging, it was about 510 MPa and approached tensile strength of the base metal (93%).