Effect of molybdenum addition on microstructure and mechanical properties of 90% tungsten heavy alloys

Abstract

Powder metallurgy approach was used to produce fine-grain tungsten heavy alloys (WHAs), and the effect of Mo addition on the microstructures and mechanical properties of the alloy was discussed. The W-Mo-Ni-Fe ultrafine composite powders were prepared via method consisting of steps of carbothermic pre-reduction and subsequent deep hydrogen reduction. The sintered compacts of these W-Mo-Ni-Fe composite powders reached virtually full densification after sintering at 1500 °C for 2 h. It was discovered that the W grain size of WHAs reduced due to the Mo addition (0, 2.5, 5, 10 wt%). Tensile test results showed that the alloy with 5 wt% Mo exhibited the maximum ultimate tensile strength and elongation, which has a significant relationship with finer W grain size, lower WW contiguity and higher volume fraction of the γ-(Ni, Fe) matrix phase. It was also concluded that the major fracture characteristic of WHAs were transformed from WW decohesion to W-matrix interface separation with increasing the addition amount of Mo.