Technical basis of using laser direct energy deposition as a high-throughput combinatorial method for DC-cast Al-Mn alloy development

Abstract

This work evaluated the technical basis of using laser direct energy deposition (DED) additive manufacturing (AM) as a rapid alloy screening method to study the phase transformation of second phase particles and recrystallization behavior of Al-Mn alloy AA3104 throughout the steps of thermomechanical processing. The study focused on assessing the differences between DED and DC-cast AA3104 alloy after homogenization and hot rolling. The fast cooling and repeated in situ thermal cycles during DED AM resulted in different phase transformation behavior compared to conventional DC-cast alloys. DED alloys exhibited a higher fraction of α-Al (Fe,Mn)-Si particles, more uniform particle distribution, and stronger cube texture in the as-fabricated condition. Homogenization promoted Al6(Fe,Mn) to α-Al (Fe,Mn)-Si phase transformation in both DED and DC-cast alloys. After homogenization, DED alloys exhibited two times as many coarse α particles in area fraction as DC-cast alloys but fewer nanoscale dispersoids. These unique material characteristics in DED alloys were responsible for easier recrystallization after hot rolling and annealing. While the differences existed, DED and DC-cast AA3104 alloys demonstrated a similar trend in phase transformation and recrystallization, strongly reinforcing that DED AM can support high-throughput Al alloy development.

Keywords

• Direct energy deposition additive manufacturing
• Aluminum-manganese alloy
• Alloy development
• Intermetallic phase transformation
• Texture
• Recrystallization