Ultrafine Grain Tungsten Heavy Alloys with Excellent Performance Prepared by Spark Plasma Sintering

Abstract

Ultrafine grain tungsten heavy alloys (WHAs) were successfully produced from the nanocrystalline powders using spark plasma sintering. The present study mainly discussed the effects of sintering temperature on the density, microstructure and mechanical properties of the alloys. The relative density of 98.12% was obtained at 1 050 °C, and the tungsten grain size is about 871 nm. At 1 000 °C-1 200 °C, the mechanical properties of the alloys tend to first rise and then goes down. After SPS, the alloy exhibits improved hardness (84.3 HRA at 1 050 °C) and bending strength (987.16 MPa at 1 100 °C), due to the ultrafine-grained microstructure. The fracture mode after bending tests is mainly characterized as intergranular or intragranular fracture of W grains, interfacial debonding of W grains-binding phase and ductile tearing of binding phase. The EDS analysis reveals a certain proportion of solid solution between W and Ni-Fe binding phase. The good mechanical properties of the alloys can be attributed to grain refinement and solid solution strengthening.

Keywords

tungsten heavy alloys / ultrafine grain / nano-crystalline powders / solid solution strengthening / spark plasma sintering