Microstructure and mechanical properties of laser beam-welded AA2060 Al-Li alloy

Laser beam welding of a newly developed AA2060 aluminum-lithium (Al-Li) alloy was performed with AlSi12 filler wire. The fusion zone (FZ) consisted of dendritic solidification structure with the LiAlSi and CuAl2 phases and a small quantity of Mg2Si phase at the dendritic and grain boundaries, reducing the precipitation ability in the interior of grains. The microhardness was decreased in the FZ, being 90-120 HV0.1, compared to the based material (BM), being 152 HV0.1, and the variation was consistent with local strength across the joint. The joint transverse tensile strength was 416 MPa and the elongation was 1.2%. The presence of grain boundary phases caused the fracture mode varied from a low-energy intergranular fracture in the FZ to a high-energy transgranular fracture in the BM. The formation of LiAlSi phases in the weld metal, resulting from the addition of Si, helped increase the tensile strength of the joints. The M2060 Al-Li alloy is considered weldable due to the over 80% tensile strength of BM in laser beam welding, which readily meets most applications. (C) 2016 Elsevier B.V. All rights reserved.