Influence of Compositional Changes on Mechanical Properties in Additively Manufactured Aluminum Alloys

Additive manufacturing (AM) is an emerging manufacturing technology that can create functional metal parts directly from a three-dimensional computer model. While there are many benefits to AM, there are also many challenges. One of the primary challenges is maintaining consistency in the deposited material throughout the entire build process. Controlling the alloy chemistry is critical for achieving this consistency. Alloys that contain highly volatile solute elements can suffer preferential vaporization which results in a change to the expected composition. The sensitivity of the alloy to the compositional change must be quantified before it can be successfully used. This study examines compositional losses in the aluminum 2139, an Al-Cu-Mg-Ag-Mn alloy, where the Mg is the volatile component. While only present in a small amount (0.5 wt%), the Mg is key to achieving the desired microstructure and properties. The Mg promotes the formation of heterogeneous co-clusters with Cu and Ag. These clusters provide nucleation sites for the strengthening precipitate Al2Cu on the {111}Al planes. Without adequate Mg, the precipitate nucleates off defects structures on the {100}Al planes, changing the strength of the alloy considerably. This presentation will examine how Mg loss affects the deposited material in aluminum alloy 2139 fabricated by AM.