Effect of Nano-Cr2O3 Dispersed W-Zr Alloys by Mechanical Alloying and Pressureless Conventional Sintering

Mechanical alloying is a preferred approach for producing tungsten (W)-zirconium (Zr)-based alloys due to their vast difference in melting point and insufficient synergic solubility. This study comprises fabrication of nano-chromium oxide (Cr2O3)-dispersed W-Zr alloys through mechanically alloying for 20 h followed by conventional sintering in inert (argon) atmosphere at 1400 and 1500 degrees C with a 2-h holding time. Alloys A, B, and C are designated as per the following compositions: 98.5W-0.5Zr-1(Cr2O3), 97.5W-0.5Zr-2(Cr2O3), and 98W-1Zr-1(Cr2O3), respectively. The effects of the Zr and Cr2O3 addition to W and sintering temperature have been discussed in relation to mechanical characteristics. The phase evaluation and microstructural behavior of the powders and sintered samples has been studied using x-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy, respectively. The powder characterization after 20 h of milling through SEM has depicted a homogeneous mixture of Zr and Cr2O3 with W. Combined addition of Zr and Cr2O3 has resulted in a bimodal grain size distribution. The enhanced grain refinement coarse/fine particle count ratio due to mechanical alloying was observed in alloy A after 20 h, which was 1.57 compared to 2.6 in alloy C. The alloy A sintered at 1500 degrees C exhibited the highest densification (91%), hardness (13 GPa), wear resistance, and compression strength (1.37 GPa) due to better fraction of fine grains, solid solution, and dispersion strengthening compared to other alloys in both sintering temperatures.