1993 Volume 57 Issue 7 Pages 821-826
The pressureless sintering densification characteristic of NiAl+Ni mixed powder, the composition of which was mainly in Ni3Al intermetallic compound and Ni+Ni3Al two phase alloy, was investigated. It was found that completely densified compacts of Ni3Al intermetallic compound and Ni+Ni3Al alloy with a large amount of Ni3Al could be obtained by controlling the powder particle size and the sintering condition, though the densification of Ni-rich (82∼100 at%Ni) sintered compacts was incomplete. These results were thought to be explained by the authors’ theory of “Equilibrium gas pressure”, i.e., “The densification in the final stage of solid phase sintering is affected by whether the equilibrium pressure of the gas (CO in this case) generated by the reduction of oxide is higher or lower than the surface stress (the driving force of the shrinkage) of the closed pores”, which have been reported in the previous papers. The bending strength and hardness of the completely densified Ni3Al intermetallic compound were 1.3 GPa and 330 HV, respectively, and those of Ni+Ni3Al alloy were 2.9 GPa and 310 HV, respectively.
