研究了NiAl-2.5Ta-7.5Cr合金在不同的退火温度下的组织演变过程,结果表明该合金的铸态组织是由NiAl基底中包含Ta(CrNiAl)2的大晶粒Laves相和一些富含Cr的尺寸在400-500nm的小颗粒组成,其中大晶粒Laves相晶界处存在C14结构相.NiAl中Ta和Cr的浓度分别在～0.6at%和～2.5at%之间.将合金置于1000℃度下退火,有细小的棒状C15结构的Laves相在NiAl中开始弥散析出.而合金经过1200℃度退火2h后,这种颗粒的体积分数增加,同时NiAl基底中Ta的浓度减少到～0.2at%.当退火温度增加到1400℃,NiAl底中的Laves析出相完全消失.因此,1000-1300℃温度范围内这种Laves相在NiAl基底中的析出,可归因于Ti元素在NiAl固溶后的过度饱和后发生扩散的缘故.
The microstructure evolution of NiAl-2.5Ta-7.5Cr alloy during annealing at different temperatures was investigated. It is found that the microstructure of the as-cast alloy consists of coarse Laves phase Ta(CrNiAl)2 with C14 structure at grain boundaries and Cr-rich particles with sizes in the range of 400-500 nm in the NiAl matrix. The Ta and Cr concentrations in the NiAl are～0.6% and～2.5% (at%), respectively. When the alloy is annealed at the temperature above 1000 ℃, fine rod-like Laves phases with C15 structure begin to precipitate dispersively in the NiAl. After annealing at 1200 ℃ for 2 h, the volume fraction of the particles increases, and in the mean time, the Ta concentration in NiAl matrix reduces to ～0.2at%. As the annealing temperature further increases to 1400 ℃, the Laves phase precipitates dissolve in the NiAl matrix completely. Therefore, the precipitation of Laves phase in NiAl during the annealing in the temperature range of 1000～1300 ℃ may be attributed to the diffusing followed by the supersaturation of Ta in NiAl after the solidification.
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