Phase transformation and thermal stability of mechanically alloyed W–Ni–Fe composite materials

The tungsten heavy alloys with the composition of 93W–4.9Ni–2.1Fe in weight percent from the elemental powders of W, Ni and Fe were mechanically alloyed (MA-ed). Nano-crystalline supersaturated solid solutions with grain size of 11 nm, and amorphous phase were achieved during MA. By using a combination of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) analysis, phase transformation and thermal stability of mechanically alloyed 93W–4.9Ni–2.1Fe alloys were investigated. The results show that the melting point of 93W–4.9Ni–2.1Fe alloy milled for 60 h decreases approximately by 220 °C compared with the unmilled powderd mixture. When sintered at 1150 °C for 30 min, tungsten heavy alloys using mechanically alloyed powders show homogeneous microstructure and ultra-fine tungsten particles of approximately 2 μm with high density above 95%. The matrix of tungsten heavy alloys, sintered at 1280 °C for 30 min using MA-ed powders, shows high W solubility about 63.72 wt.% with a large amount of volume fraction of about 0.5 of matrix.