Nanostructured Mo3Al-based composites strengthened by Al2O3 precipitates

Nanostructured Mo3Al-based composites strengthened by Al2O3 precipitates were obtained from a Mo75Al25 (at.%) + 15 vol.% Al2O3 mixture that was synthesized by mechanical alloying (MA) from Mo, Al and Al2O3 powders and subsequently annealed. The influence of rotation speed and milling time on the structure and mechanical properties of the final compacts, before and after annealing, was studied. After milling at 150 and 300 rpm, mainly a metastable BCC-Mo(Al) solid solution was observed. With subsequent annealing at 900 °C this solid solution decomposed into Mo + Mo3Al (an intermetallic phase). The mechanical properties of the samples mechanically alloyed at 300 rpm are in general better than the ones of samples alloyed at 150 rpm. Values of H = 18.4 GPa, σy = 6.2 MPa and E = 227 GPa were obtained from the 300 rpm samples, after annealing at 900 °C. The work-hardening coefficient value, n, obtained from the annealed sample milled at 150 rpm is higher than the one from the as-milled sample (0.05 in contrast to 0.02, respectively), indicating a slight increase in ductility. For 300 rpm no significant variation of n was apparent after annealing (n was about 0.02).