Effect of post-heat treatment on microstructure and mechanical properties of laser welded Al-Cu-Mg alloy

Abstract

A new approach was developed to improve strength of Al-Cu-Mg alloy laser welded joints that typically within 61–90 % of that of the base metal due to a change in the microstructure and phase composition of the weld one. This result was achieved by optimization of post weld heat treatment (PWHT) included quenching and subsequent artificial aging. For the first time, the spatial distribution and evolution of the phase composition were studied at all PWHT stages using high-resolution scanning electron microscopy and synchrotron X-ray analysis. It was found that the Al-Cu-Mg solid solution was homogenized, as well as the S(Al2CuMg) strengthening and (partly) θ(Al2Cu) phases were formed. After PWHT, ultimate tensile strength was 428 MPa, yield strength was 302 MPa, and elongation was 19.6 %, which were 99 %, 98 % and 95 %, respectively, of those of the base metal.