利用金相、扫描电镜、透射电镜观察了Ni3Al+Ni7Hf2共晶合金的微观组织结构，并利用高梯度定向凝固技术研究了该合金的凝固行为．结果表明：Ni—5．8Al—32Hf由Ni3Af＋Ni7Hf2共晶组成，是Ni3Al／Ni7Hf2共晶复合材料的合适成分由于不平衡凝固，有害相β-NiAl与金属间化合物Ni7Hf2以共晶体的形式存在于共晶胞间，在一定的温度梯度下，可以通过降低生长速度的方式予以消除．Ni-5．8Al-32Hf的凝固温度范围为41℃，临界凝固稳定性因子（即G／R）为5×105℃.s／cm2，在该条件下制备出以Ni7Hf2为增强相、以Ni3Al为基的定向凝固片状共晶复合材料.
The Ni3Al+Ni7HfZ unidirectionally soliditied lamellar eutectic has been studied to improve the transversal ductility and interface-thermal-stability of the ordinary eutectic composites in situ. The microstructure of Ni-5.8Al-32Hf (mass fraction,%) alloy was investigated in detail by means of metallography, transmission electron microscopy (TEM) and electron probe. The solidification behaviour of Ni3Al+Ni7Hf2 eutectic alloy was investigated at different temperature gradient (G) and solidilication rate (R). The results show that Ni-5.8Al-32Hf alloy with Ni3Al+Ni7Hf2 eutectic structure is considered to be the proper compositon. Some brittle β-NiAl phase in the alloy can be avoided by decreasing soliditied rate. Melting range of the alloy above mentioned composition is 41℃ determined by DTA. The critical value of G/R for NisAl+Ni7Hf2 eutectic is 5×105 ℃·s/cm2, and the lamellar Ni3Al+Ni7Hf2 eutectic aligned parallel to the direction of solidilication was obtained under R=5μm/s and G=250℃/cm.
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