Influence of Heating Temperature on Microstructure Characteristics of Directionally Solidified Ni-45Ti-5Al Alloy

摘要

The microstructure evolution of Ni-45Ti-5Al(atomic fraction,％) alloys prepared by directional solidification with liquid-metal-cooling at different temperatures of 1450°C,1550°C and 1650°C was investigated.The results showed that the macrostructure in directional solidification growth region was obvious columnar grains.The microstructure was cellular growth structure,and composed of primary NiTi matrix and Ti2Ni precipitates.The preferred orientation of NiTi and Ti2Ni were respectively [100] and [111] direction.It was found that aluminum was dissolved in both NiTi and Ti2Ni phase.The Al content in the matrix was higher than it in the precipitates.As heating temperature increasing,the microstructure evolution was inconspicuous and the average cellular spacing was 30～50μm.The Ti2Ni volume percent was most when the heating temperature was 1550°C.