Heating rate effects on micro structural properties of liquid phase sintered tungsten heavy alloys

摘要

Dimensional precision is one of the prime concerns in forming net-shape bodies by liquid phase sintering. The factors that lead to densification can also cause distortion, leaving a narrow processing window in which to achieve densification without distortion. This paper reports the effect of heating rate on liquid phase sintering of W-Ni-Fe heavy alloys. Heavy alloys with compositions of 83, 88, and 93 wt. percent W, balance Ni-Fe in the ratio 7:3, were sintered at heating rates of 1, 5, 10, and 15 deg C/min. Over this range, heating rate did not have a significant effect on densification nor distortion. Critical values of contiguity and connectivity were identified that separate distortion from shape preservation. The grain size distributions produced by different heating rates are self-similar. A previously proposed cumulative intercept grain size distribution function gives a good fit to the grain size data. The mean grain growth rate constant is 2.8 mu m~3/s. The grain growth rate constant varies inversely with the volume fraction of liquid to the 2/3 power.