Investigation on the Thermal Stability of Directionally Solidified NiAl-32V Hypoeutectic Alloy

Abstract:

In this paper, the NiAl-32V pseudo-binary hypoeutectic alloy was prepared by directional solidification technology. The microstructure morphology of the alloy in the steady-state region at different withdrawl rates after high temperature heat treatment was studied, and the variation of its thermal stability and microstructure morphology was analyzed. The results indicates: The primary phase of the alloy has good thermal stability at 900°C(5~100h). The coarsening and spheroidization of NiAl eutectic layers are observed, and the longer the heat treatment time is, the greater the coarsening degree is, and the more obvious the spheroidization is. After high temperature heat treatment at different temperatures(900°C,1000°C,1100°C)for 5 h, the proportion of primary phase area of the alloy also changed slightly. The coarsening and spheroidization of NiAl eutectic lamellae were observed in all samples (withdrawl rates V=6~150μm/s). With the increase of heat treatment temperature, coarsening and spheroidization are more obvious.