SPS densification behavior of W-5.6Ni-1.4Fe heavy alloy powders

Abstract

Spark plasma sintering (SPS) method was used to sinter two different types of 93W-5.6Ni-1.4Fe (wt pct) heavy alloy powders which were respectively prepared by simple mixing and high-energy ball milling (HEBM) for 40 h. In SPS processing, the powder compacts were heated at 100 °C/min to the desired sintering temperature with 5 min holding. The SPS densification behavior of the two types of powders was investigated. For the simple mixed powders, the compacts start to shrink around 850 °C, and the densification is enhanced by diffusion and plastic deformation with the increase of temperature. Consequently the compacts shrink effectively and obtain nearly full density around 1230 °C. While for the as-milled powders, recovery and recrystallization occur between 700–850 °C due to the crystal lattice distortion and defects resulted from HEBM, causing the soften of particles and a slight shrink of compacts. When increasing temperature, nanosintering of W crystallines in the matrix occurs in the inside of the composite powders, and the densification rate accelerates and maximizes at about 1050 °C. Owing to the improved activity of powders from HEBM, the tungsten grains coarsen rapidly in the sintering, simultaneously, the harmful intermetallic phases Ni2W4C and Fe6W6C are generated.