NiAl-Mo共晶复合材料定向凝固组织特性研究

采用定向凝固技术制备出两种不同成分的NiAl-Mo共晶复合材料,研究在不同抽拉速率下该合金的凝固组织特性.结果表明:46.59Ni-45.61Al-7.8Mo(at%,下同)合金在不同抽拉速率下都形成了亚共晶组织,初生的NiAl相呈树枝晶状,并且随着抽拉的进行,优先生长方向与热流方向不一致的枝晶被逐渐淘汰;随着抽拉速率的增加,NiAl相的枝晶间距也不断的减小.44.86Ni-46.3Al-9.01Mo合金在不同抽拉速率下皆形成以棒状Mo相镶嵌在NiAl基体中的共晶组织,随着抽拉速率的增加,Mo相的平均直径和平均棒间距有越来越小的趋势,在抽拉速率达到14 mm/h以上时,Mo相由连续的、排列均匀的棒状变为断续的、排列不均匀的棒状.

Study on Characteristics of Directionally-Solidified Microstructure for NiAl-Mo Eutectic Composites

NiAl-Mo eutectic composites with two kinds of composition, 46.59Ni-45.61Al-7.8Mo and 44.86Ni-46.3Al-9.01Mo(at%), were prepared by directional solidification technology. The characteristics of solidification microstructure for the alloys at different withdrawing rates were studied. Results show that the microstructure of 46.59Ni-45.61Al-7.8Mo alloy was hypoeutectic at different withdrawing rates. The primary NiAl phase was dendritic; those initial dendrites disappeared gradually as their preferred growth direction did not coincide with the direction of heat transfer during the vertical directional solidification. With increase of the withdrawing rate, the dendrite arm spacing of NiAl phases was decreased little by little. For the 44.86Ni-46.3Al-9.01Mo alloy, eutectic microstructure of rod-like Mo phases inserted in NiAl matrix was formed at different withdrawing rates. With the increase of the withdrawing rate, both of the average spacing and the average diameter of the Mo phases decreased. When the withdrawing rate exceeded 14 mm/h, the continuous and regularly-ranged rod-like Mo-phase turned to irregular and discontinuous