Effect of Si addition on phase evolution and microstructure in Y2O3 dispersed tungsten (W) and W-based alloys synthesized via mechanical alloying and consecutive conventional sintering

Abstract

The present research reports the fabrication of nano-scale yttria (0.3 wt%) dispersed pure W, W-10Ni, W-10Ni-3Co, W-1Si, W-10Ni-1Si,and W-10Ni-3Co-1Si alloys by mechanical alloying (MA) of W, Ni, Co, Y2O3, and Si powders for 10 h and consecutive consolidation via conventional sintering under H2 gas atmosphere at 1500 °C for 2 h. It has been found that the addition of 1 wt% Si causes a faster reduction in particle size and results in more fine and uniform particles. The X-Ray diffraction (XRD) and transmission electron microscopy (TEM) analysis reveal the formation of nano-scale WSi2 intermetallic compound in the W-1Si-0.3Y2O3 alloy and it is observed that the Ni and Co addition prevent the formation of the intermetallic compound in the W-Si alloy systems during milling. However, the appearance of intermetallic W5Si3 in W-1Si-0.3Y2O3 alloy and SiO2 oxide phase in W-10Ni-1Si-0.3Y2O3 and W-10Ni-3Co-1Si-0.3Y2O3 alloys are observed after sintering. The values of crystallite size, relative density, and hardness values are measured for investigated alloys. Sintered densities of 95% and 96% are observed in the case of W-10Ni-1Si-0.3Y2O3 and W-10Ni-3Co-1Si-0.3Y2O3 alloys respectively. The highest hardness value of 5.4 GPa is observed in W-1Si-0.3Y2O3 alloy with a sintering density of 82.3%. The highest density (96% relative density) and compressive strength of 1.5 GPa are found in W-10Ni-3Co-1Si-0.3Y2O3 alloy.