The Effect of the Preparing Methods of Ni+Al Powder Blends on Reaction Sintering Features and Properties of NiAl Compacts

摘要

The effect of the preparation methods of powder blends by traditional milling (Ni+Al particles), short time attritoring (Ni/Al composite particles), plating of Ni by Al or Al by Ni (Ni/Al or Al/Ni composite particles) on the structure, internal stresses and ability to reaction sintering (RS) or high temperature self propagating synthesis (HTSPS) of these powder blends and the structure, phase composition and properties of NiAl compacts was investigated. The reaction (at T ≥ 650℃) between Ni and Al in Ni-50 at.%Al (β-phase, B2) powder alloy occurs in some steps through the formation of Al-melt (liquid-phase reaction) and lower-melting NiAl_3, Ni_2Al_3, (Ni_3Al) aluminides. The deformation strengthening of Ni and Al powders under mechanical alloying in attritor (16 h) intensifies the mass transport and decreases temperature of the beginning of exothermic reaction Ni+Al reversible NiAl up to ≥ 300℃ (solid-phase reaction). The plating of Ni by Al is more favorable for the development of HTSPS. Compacts with a density of 99% of the theoretical one was obtained. The bending strength at temperatures up to 1100-1200℃ were studied.