Microstructural characterization of the directionally-solidified Ni-Al-Mo-Ta eutectic alloy

摘要

This research aims at microstructural characterization of a directionally-solidified Ni-Al-Mo-Ta eutectic alloy (=DS rod). The microstructures consisted of matrix which is composed of NiaAl and Ni with fibrous and lamellar reinforcement phase which is composed of Mo. Detailed qualitative metallographic examinations were conducted on the directionally-solidified rods. The composition of specimens is Ni-5.26mass%Al-35.5mass%Mo-X%Ta(X=0,3,7 mass%). We chose Ta as a 4th additional element. Many dendrites were observed at the bottom end of DS rods, and the amounts of dendrites were decreased with the advance of solidification. Stable microstructures without dendrites were observed in the upper part 70mm from bottom. The relationship between solidification rate and microstructure was experimentally investigated.