Effect of high energy ball milling on structure and properties of 95W-3.5Ni-1.5Fe heavy alloys

In this article, an attempt is made to prepare tungsten heavy alloy (WHA) powder by high energy ball milling of 95 wt% W, 3.5 wt% Ni and 1.5 wt% Fe in a dual drive planetary ball mill (DDPBM). The present study mainly focusses on the effect of milling on density, microstructure and mechanical properties of sintered WHAs. The minimum crystallite size of 18 nm was observed in 15 h milled WHA powder. Sintering of WHAs was carried out at 1500 °C for 1 h in hydrogen atmosphere. The sintered samples prepared from un-milled and ball milled WHA powders were characterized for microstructure (SEM equipped with EDS) and mechanical properties (Rockwell hardness and nanoindentation). The internal attributes and uniformity in distribution of W spheroids in sintered WHA were investigated with X-ray microcomputed tomography (X-ray μ-CT). All sintered samples exhibited sintered density in the range of 97.1 to 98.6% theoretical. Uniform distribution of W spheroids in Ni-Fe matrix was observed in sintered samples. The mean grain size of sintered WHAs varies in the range of 22.7-31.1 μm and W-W contiguity (CWW) ranges from 0.58-0.69. Despite relatively less density (97.1%), the sintered WHA prepared from 15 h milled powder offered good combination of bulk hardness ~ 64.8 HRA and elastic modulus ~ 431 GPa.