Nanostructured oxide dispersion strengthened Mo alloys from Mo nanopowder doping with oxide nanoparticles

Abstract

A simple and efficient pathway was developed to synthesize ultrafine grained oxide dispersion strengthened (ODS) Mo alloys doped with nano-scaled oxide particles. Firstly, dispersed La(NO3)3 or Al(NO3)3 nanoparticles were introduced into commercial MoO3 via a solution spraying method. Then, Mo nanopowders containing different amounts of oxides nanoparticles (La2O3 (0%, 0.5%, 1% and 2%) or Al2O3 (0.5%, 1%)) were successfully prepared by reducing the doped MoO3 with carbon black at 600 °C and 1050 °C, and hydrogen at 800 °C. Due to the high sintering activity of prepared doped Mo nanopowder, after sintering in H2 at 1300 °C for 3 h, the relative density of sintered products containing 0.5% La2O3 or Al2O3 reached to above 95.4%. Nanostructured ODS Mo alloys with Mo and La2O3 (or Al2O3) grain sizes of about 0.5 μm and 75 nm (or 50 nm for Al2O3) were successfully prepared at around 1300 °C. The obtained nanostructured Mo-oxides alloys had much high hardness values. For the Mo-La2O3 alloys, the highest value of hardness can reach to 338 HV (1% La2O3, Mo grain size, 0.51 μm; La2O3 grain size, 71.3 nm; density, 93.0%), while the highest hardness of Mo-Al2O3 alloys reached to 385 HV (1% Al2O3, Mo grain size, 0.55 μm; Al2O3 grain size, 55.9 nm; density, 94.6%), which were much higher than the ODS-Mo alloys prepared from the traditional methods. This method could also have great potential for industrially producing nanostructured ODS Mo alloys and W alloys.