Microstructure and mechanical properties of W-HfC alloy synthesized by in-situ fabrication via pressureless sintering

Abstract

The materials, primarily utilized in the manufacturing process, significantly impact the microstructure and mechanical properties of W-HfC alloys. In this study, different initial composition, such as HfH₂/WC, HfH₂/C and HfC, were respectively mixed into W powders, three categories of W-HfC alloys (abbreviated as WHC1, WHC2 and WHC3 successively) were fabricated by in-situ reaction sintering methods. The microstructure and mechanical properties of three alloys were investigated comparatively by using X-ray diffraction, electron microscopy and high temperature tensile tests. The results revealed that WHC2 alloy presents an exceptional ductile-brittle transition temperature of ∼300 °C and the best comprehensive performance. Tensile testing at 300 °C indicates that WHC2 alloy exhibits a complete plastic fracture curve with a tensile strength of 400 MPa and a residual deformation of 9 %, as well as the plasticity enhancement. It is mainly attributable to the dispersion strengthening effect of second phase particles at grain boundaries and within W-matrix grains. Furthermore, the excellent overall performance of the WHC2 alloy demonstrates that the in-situ reaction can significantly reduce sintering difficulties, while the resultant second phase particles provide considerable advantages in improving the properties of W-based alloys. These findings provide valuable insights into the synthesis process and mechanical performance of W-HfC alloys, enabling advancements in their application in high-temperature environments.