真空铜模吸铸高Nb-TiAl合金快速凝固显微组织演化及凝固路径  

Microstructural Evolution and Solidification Paths of Rapidly Solidified High Nb-Containing TiAl Alloy Prepared by Vacuum Suction Casting

作　　者：柳翊 朱德荣 闵志宇[1,2] 李妙玲 陈智勇 李豪 张伟[1,2] LIU Yi;ZHU De-rong;MIN Zhi-yu;LI Miao-ling;CHEN Zhi-yong;LI Hao;ZHANG Wei(School of Materials Science and Engineering,Luoyang In stitute of Science and Technology,Luoyang 471023,Henan,China;Henan Intelligent Manufacturing Engineering Technology Research Center for Building Profile,Luoyang 471023,Henan,China;School of Mechanical Engineering,Luoyang Institute of Science and Technology,Luoyang 471023,Henan,China)

机构地区：[1]洛阳理工学院材料科学与工程学院,河南洛阳471023 [2]河南省建筑型材智能制造工程技术研究中心,河南洛阳471023 [3]洛阳理工学院机械工程学院,河南洛阳471023

出　　处：《铸造》2021年第7期823-827,共5页Foundry

基　　金：河南省高等学校重点科研项目(21B430012、16A430020);河南省科技攻关项目(212102210285、212102210284、212102210588);洛阳理工学院高层次人才科研启动项目(2017BZ05)

摘　　要：采用真空铜模吸铸技术制备了尺寸为Φ5 mm x 90 m m的Ti-45Al-8.5Nb-(W,B,Y)(at.%)合金棒状试样,研究了急冷快速凝固显微组织演化及凝固路径。结果表明:基于Ti-Al-8.5Nb三元合金系的变温截面图与铸态凝固组织特征,该铸态合金凝固路径是单一β相凝固,初生相为β相,其主要相组成为α2相、γ相及β2相以及少量硼化物和氧化钇颗粒;与铸态相比,表面急冷区凝固组织具有明显的单一β相凝固特征,而糊状区枝晶形貌明显且存在包晶晕,为典型的包晶凝固,从急冷区至糊状区,其凝固方式由单一β相凝固向包晶凝固转变;在表面急冷区,脉络状B2相、针状硼化物、氧化钇颗粒以及片层结构(α2+γ)的形成一定程度上被抑制,随着冷却速率的提高,α2相(002)和γ相(111)面的衍射峰向高角度偏移约0.6°。Rod samples(Φ5 mm×90 mm) of Ti-45 Al-8.5 Nb-(W, B, Y)(at.%) alloy were prepared by Cu-mold vacuum suction casting to investigate the effects of cooling rates on the microstructural evolution and solidification paths of high Nb-containing TiAl alloy. By vertical section diagram of Ti-Al-8.5 Nb ternary system and its as-cast microstructure characteristics, it can be determined that the solidification path of the alloy is a single β-phase solidification and primary solidification phase is β phase. The microstructure of the alloy is composed of α2 phase, γ phase and B2 phase as well as small amounts of borides and yttrium oxide particles. Compared with as-cast alloy, the solidification microstructure in quenched zone has obvious solidification characteristics of single β-phase, while the dendrite morphology in mushy zone is obvious and there is peritectic halo, which shows typical peritectic solidification. From quenched zone to mushy zone, the solidification mode changes from single β-phase solidification to peritectic solidification. The formation of vein-like B2 phase, acicular borides, yttrium oxide particles and lamellar structures(α2+γ) is inhibited, to a certain extent, due to rapid cooling in the surface quenching zone. With an increase in the cooling rate, the diffraction peaks of α2 phase(002) and γ phase(111) planes shift to a higher angle by about 0.6°.

关 键 词：吸铸 凝固路径 β相凝固 糊状区 包晶凝固 

分 类 号：TG146.2[一般工业技术—材料科学与工程]