电子束选区熔化成形及后续热处理后Ti-47Al-2Nb-2Cr合金显微组织

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

摘要:

对电子束选区熔化成形及后续热处理后Ti-47Al-2Nb-2Cr合金显微组织进行了分析,讨论了成形过程中合金凝固和固态相变过程。研究结果显示：电子束选区熔化成形Ti-47Al-2Nb-2Cr合金的显微为细小的γ-TiAl 和 α₂-Ti₃Al形成的片层结构,但是由于电子束选区熔化成形过程冷却速度较快和成形过程中的热循环作用,成形样品的片层晶团和片层间距皆沿样品成形方向从上到下变大。合金的凝固过程通过了β单相区,并经历L → L β → β → β α → α → α γ的相变过程。为了得到均匀一致的显微组织,对电子束选区熔化成形样品进行了热处理,通过1250℃油淬后1200℃保温2小时,得到了细小均匀的片层结构组织。

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.