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 W W 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 W W decohesion to W-matrix interface separation with increasing the addition amount of Mo.
In this study, the Al-B-Mo alloy powders with a boron content of 7 wt % and Molybdenum content of 0.5–3 wt % were prepared by the close-coupled gas atomization. The powder morphology, phase composition, oxidation, and exothermic behavior of combustion were characterized. The results show that the addition of Mo effectively improves the energetic properties of the alloy powder, with the mass-burning enthalpy of Al-7B-1Mo reaching 31111 J/g, exceeding the theoretical mass-burning enthalpy of monolithic Al (31000 J/g). Al-7B-1Mo underwent a violent exothermic process at around 1000 °C, and the oxidation weight gain ratio and oxidation efficiency reached 46.16 % and 48.05 % respectively, an increase of 19.75 % and 21.08 % compared to Al-7B. The mesh structure formed by the AlB 2 phase on the particle surface positively promoted the particles′ thermal oxidation. Mechanical mixtures of AlB 2 /Mo and AlB 2 /MoO 3 were prepared and the catalytic promotion of the combustion of AlB 2 by Mo and MoO 3 was confirmed by thermal tests of combustion. The mechanism by which Mo/MoO 3 promotes the combustion of AlB 2 was investigated through the phase composition characterization of the composite powder after heat treatment in argon and air atmosphere. It was confirmed that MoO 3 promotes the oxidation and combustion of AlB 2 by supplying oxygen to B in AlB 2 , while Mo is first oxidized to MoO 3 , which then promotes the combustion of AlB 2 .
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