Research on Microstructure and Heat Treatment of Ni₃Al Alloy Formed by Laser Direct Deposition

The microstructure of high-boron Ni₃Al alloy formed by laser direct deposition and the effect of heat treatment on the alloy were studied.The results show that the microstructure of laser-deposited Ni₃Al alloy is mainly composed of γ+γ'eutectic phases, γ' phase and boride. During the solution treatment, the irregularly shaped γ' phase and the boride are dissolved, but as the solution temperature increases, the β-NiAl phase is precipitated in the alloy structure. During the aging process, the γ'phase and the boride are precipitated.It is re-precipitate from the matrix phase, and the new γ'phase and boride are finer and more dispersed. After 1080 ℃×4 h, AC+900 ℃×10 h, AC solution aging treatment, the alloy not only obtains fine dispersed γ' phase and boride reinforced structure, but also effectively inhibits the β-NiAl phase precipitation, which improves the mechanical properties of the alloy.