From crack-prone to crack-free: Eliminating cracks in additively manufactured Ti-48Al-2Cr-2Nb alloy by adjusting phase composition

Abstract

At present, it remains a challenge to additively manufacture Ti-48Al-2Cr-2Nb (TiAl4822) alloy by laser powder bed fusion (LPBF) technology because of the severe cracking in the building process. In this work, it was found that cracks in LPBFed TiAl4822 alloy were more likely to occur in the region near the interfaces between α2 and B2 phases, and the underlying mechanism was addressed. This leads to a strategy to reduce or eliminate these cracks via reducing the phase interfaces between α2 and B2 phases by adjusting its phase composition. Through the design of LPBF process parameters, the purpose of adjusting phase composition of LPBFed TiAl4822 alloy in a wide range (from nearly α2 single-phase, to α2 + B2 + γ, and then to nearly B2 single-phase) was realized. As expected, with the reduction of the interfaces between α2 and B2 phases, the cracking behavior has been significantly alleviated. The exciting result was that the crack-free sample could be achieved in the LPBFed TiAl4822 alloy with nearly α2 single-phase structure. Its compressive strength was measured to be 1460.7 MPa comparable to that of its casting counterpart. The present work makes it possible to additively manufacture crack-free TiAl4822 alloy by tuning phase composition.

Keywords

• Laser powder bed fusion
• Ti-48Al-2Cr-2Nb
• Cracking
• Phase composition