采用高温度梯度定向凝固装置制备NiAl--28Cr--5Mo--1Hf(原子分数, %, 下同)共晶合金,研究了高温热处理对合金显微组织和显微硬度的影响. 结果表明,热处理后, NiAl和Cr(Mo)的层片状组织形貌基本没有变化,而合金中分布于胞界的半连续的Heusler (Ni$_{2}$AlHf)相部分或大部分消失,并以弥散的Heusler颗粒形式在NiAl基体中重新析出. 此外,Cr(Mo)相中的NiAl微粒粗化, 在Cr(Mo)相中出现了位错线. 定向凝固NiAl--28Cr--5Mo--1Hf合金的显微硬度明显高于NiAl--28Cr--6Mo合金, 热处理后, 合金的硬度值基本保持不变.
The influence of high temperature heat treatment on microstructure and microhardness of (DS)NiAl--Cr(Mo)--Hf eutectic alloy fabricated with directional solidification under high temperature gradient was investigated. The results indicate that there is little change in the morphology of NiAl and Cr(Mo) phases after high temperature heat treatment. But the semicontinuous Heusler phase which is originally located on the grain boundaries is partially reduced and fine Heusler particles re--precipitated within NiAl matrix. Furthermore, NiAl precipitates coarsen in the Cr(Mo) phase and dislocation appears in the Cr(Mo) phase. Microhardness of as--fabricated (DS)NiAl--28Cr--5Mo--1Hf alloy is much higher than that of (DS)NiAl--28Cr--6Mo and basically unchanged after heat treatment
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