Microstructure and Mechanical Properties of Wire + Arc Additively Manufactured 2050 Al–Li Alloy Wall Deposits

Abstract

Aluminum–Lithium (Al–Li) alloy is a topic of great interest owing to its high strength and light weight, but there are only a few applications of Al–Li alloy in wire + arc additive manufacturing (WAAM) process. To identify its feasibility in WAAM process, a special AA2050 Al–Li alloy wire was produced and employed in the production of straight-walled components, using a WAAM system based on variable polarity gas tungsten arc welding (VP-GTAW) process. The influence of post-deposited heat treatment on the microstructure and property of the deposit was investigated using optical micrographs (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), hardness and tensile properties tests. Results revealed that the microstructures of AA2050 aluminum deposits varied with their location layers. The upper layers consisted of fine equiaxed grains, while the bottom layer exhibited a coarse columnar structure. Mechanical properties witnessed a significant improvement after post-deposited heat treatment, with the average micro-hardness reaching 141HV and the ultimate tensile strength exceeding 400 MPa. Fracture morphology exhibited a typical ductile fracture.