Microstructures of as-fabricated and post heat treated Ti-47Al-2Nb-2Cr alloy produced by Selective Electron Beam Melting (SEBM)

Abstract:

Microstructures of as-fabricated and post heat treated Ti-47Al-2Nb-2Cr (at.%)alloy produced by selective electron beam melting (SEBM) were examined, solidification path and phase transformation of Ti-47Al-2Nb-2Cr alloy during SEBM process were also analyzed .Results show that microstructure with fine fully lamellar (FL) consisted of γ-TiAl and α₂-Ti₃Al was formed in the as-fabricated TiAl sample. Due to the rapid cooling and the cyclic heat treatment during the SEBM process, solidification took place solely through the β phase, phase transformation path was L → L β → β → β α → α → α γ and the lamellar colonies and lamellae all coarser from the top to the bottom of the specimen. Different post heat treatment were carried out to got a homogeneous microstructure .A fine and homogeneous microstructure was achieved after oil quenching from 1250℃ and holding at 1200℃ for 2h.