Dissolution and Development of Al₃(Sc, Zr) Dispersoids in Structures Produced Via Wire Arc Additive Manufacturing

Abstract

Aluminum alloys are of growing interest in fields requiring lightweight structural materials and are common in additive manufacturing applications. Aluminum wire-arc additive manufacturing (WAAM) as a method of production is also increasing in development and use, predominantly using available welding filler alloys (i.e. 5356, 5183, etc.) as feedstock. As a manufacturing method, there is an interest in pursuing new aluminum alloy development to produce superior strengths to currently available materials. Alloys of aluminum and scandium offer increased strength as well as post-processing heat treatability that makes them well suited as a feedstock for WAAM applications, however, the complex thermo-mechanical history of wire production, as well as the thermal input during WAAM processing, has a significant impact on the precipitation, dissolution, structure, and morphology of Al₃Sc dispersoids. In this work, aluminum alloy 5025 is used to produce WAAM structures, and the resulting material properties and characteristics are analyzed. Transmission electron microscopy is used to study Sc dissolution, Al₃X dispersoid morphology, and dispersoid chemistry in WAAM samples in both the feedstock and as-printed conditions. Suggestions are made for optimizing Al-Sc alloys in WAAM applications.

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