研究了B、Hf、Y微合金化高铌TiAl基合金的铸态及热处理后的微观组织。光学显微组织观察表明, B、Hf、Y微合金化高铌TiAl合金铸态组织为近层片组织, 其α2/γ层片团得到细化;XRD分析表明, 除了α2和γ相, 在铸态组织中还含有β(B2)、Y2O3、YAl2。扫描电镜结合能谱分析表明, β(B2)相分布在层片团的边界附近, 粒状Y2O3和YAl2分布在晶内和晶界, 硼化物以条状或粒状分布在晶内和晶界。经过1260℃/20h + 900℃/30min/AC热处理后, 得到由α2/γ细小层片团与等轴γ晶粒组成的双态组织, β(B2)相基本消除, 同时YAl2相消失, 形成了富Hf的Y2O3和富Nb的钛硼化物。
The as-cast and heat-treated microstructure of B, Hf, Y micro-alloyed TiAl-based alloy with high Nb content were investigated. The OM observation shows that, the as-cast microstructure of B, Hf, Y micro-alloyed TiAl-based alloy was near lamellar microstructure in which α2/γ lamellar colonies were refined. The XRD analysis shows that, besides α2 and γ phase, β(B2), Y2O3, YAl2 were also included in the as-cast microstructure. The analysis of SEM combined with EDS shows that the β(B2) phase was distributed near the lamellar colonies grain boundaries, granular Y2O3 and YAl2 , and granular or strip boride existed in grains and grain boundaries . After heat treatment at 1260℃ for 20h, at 900℃ for 30min and subsequent air-cooling, the duplex microstructures composed with thin α2/γ lamellar and γ equiaxed axis grains were obtained in the alloy, the β(B2) phase has been basically eliminated, simultaneously the YAl2 has disappeared, and meanwhile Hf-rich Y2O3 and Nb-rich titanium boride phases formed.
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