A new Al-Cu alloy for LPBF developed via ultrasonic atomization

Abstract

Wrought 2xxx aluminum alloys are difficult to process by laser powder bed fusion (LPBF) because of the hot cracking susceptibility caused by their large solidification range. Although several studies on Ti and Zr additions to 2xxx Al-Cu alloys show improved processability in LPBF, only few explore the addition of alternative alloying elements such as Cr and Fe. There is thus little knowledge on the ability of these elements to avoid hot cracking. In the present work, a new Al-Cu alloy with Ti, Cr and Fe additions is put forward and the mechanisms impeding hot cracking formation are analyzed. (Al, Cr)3Ti_L12 precipitates are formed during the solidification process, promoting heterogenous nucleation and grain refinement. Cr not only contributes to solid solution strengthening but also supports the stabilization of the Al3Ti metastable cubic phase. The addition of near-eutectic Fe decreases the solidification range, further reducing the susceptibility for hot cracking. Nano-hardness mapping reveals the solidification path of the alloy, with higher values associated with the highly dense areas of precipitates forming at the melt pool boundaries. A novel printable alloy with hardness values exceeding those of existing Al alloys for LPBF was designed.

Keywords

• Additive manufacturing
• Laser powder bed fusion
• Aluminum alloys
• Alloy design
• Precipitation
• Titanium