Sintering Behavior of Fe-W and Fe-Ni Alloys at High Temperature

Abstract

In order to examine sintering behavior in a and γ phases of iron based mixed powder compacts, sintering process of iron and wolfram mixed powders was studied, and sintering rate of iron-wolfram and iron-nickel alloys were further studied quantitatively by measurements of neck growth between their wires. The results were summarized as follows:
(1) Neck growth rate of iron-wolfram alloy wires was remarkably larger in a phase than in γ phase, although the difference in the sintering rate was not clear in the mixed powder compacts as well as in the case of iron-molybdenum system.
(2) The neck growth rate followed the theoretical equation for volume diffusion controlled rate in both a and γ phases, and its rate was obviously divided into three groups at given sintering temperatures which were assigned to a, a+γ and γ phases.
(3) Addition of W powder was found to be effective for densification of the mixed powder compacts sintered at high temperature of 1300°C, although there was little effect of its addition up to 1200°C because W slowly diffused to γ iron phase.
(4) The neck growth rate of Fe-Ni alloy wires was nearly equal to that of pure iron in γ phase, and it was not so accelerated in the alloy wires as in the case of Fe-Ni mixed powder compact.