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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。结果表明,电子束选区熔化成形Ti-47Al-2Nb-2Cr合金的显微为细小的γ-Ti Al和α_2-Ti_3Al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宽度皆沿样品成形方向从上到下变大变宽。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 h,得到了细小均匀的片层结构组织。
The microstructure of the Ti-47Al-2Nb-2Cr alloy after the electron beam selective melting and subsequent heat treatment was analyzed. The solidification and solid phase transformation of the alloy during the forming process were discussed. The results show that the microstructure of Ti-47Al-2Nb-2Cr alloy melted by electron beam is small and the lamellar structure is formed by γ-TiAl and α_2-Ti_3Al. However, due to the rapid cooling and forming During the process of thermal cycling, the lamellae and lamella widths of the formed samples all increase and broaden from top to bottom along the direction of sample formation. The solidification process of the alloy passes through the β-phase region and undergoes the phase transition of L → L + β → β → β + α → α → α + γ. In order to obtain a uniform microstructure, the samples were heat-treated by electron beam selective melting, and then annealed at 1250 ℃ for 2 h at 1200 ℃ to obtain the microstructure of fine and uniform lamellar structure.