Fabrication of nanocrystalline supersaturated W–Al alloys with enhanced thermal stability and high sinterability

In this work, nanocrystalline W–Al alloys (up to 20 at.% of Al) were produced by high energy ball milling and powder microstructural evolution was investigated as a function of milling time. It was found that, regardless of the composition, alloys crystallite size progressively decreases and stabilizes around a value of about 10–15 nm after 70–100 h of mechanical treatment. The aluminum dissolution into the bcc W lattice was confirmed by DSC, SEM, and TEM. The formation of intermetallic compounds was detected neither during ball milling nor after thermal treatments up to 1450 °C. Sintering behavior of mechanically alloyed W–Al alloys was tested under pressureless conditions, and a significant improvement in terms of sinterability with respect to pure W was observed. Along with favoring the sintering process, the addition of Al also resulted in a notable enhancement of the coarsening resistance. Indeed, the analysis of ball-milled pure tungsten after thermal treatment at 1450 °C provided an estimated average crystallite size of about 2 μm, while W80Al20 and W90Al10 alloys retained an average crystallite size of about 70 nm and 60 nm, respectively. Although further work is required to optimize sintering conditions for achieving full density samples, the retaining of the nanostructure marks a significant advancement in the field of W-based alloys.