Ductilization of Mo-Si solid solutions manufactured by powder metallurgy

Mo-1.5 at.% Si alloys with additions of either Y₂O₃ or Zr were manufactured by mechanical alloying. The Y₂O₃ particles reduced the grain size and increased the room temperature strength, but did not alleviate the brittleness of previously investigated Mo-1.5 at.% Si without Y₂O₃. Additions of Zr, on the other hand, resulted not only in a fine grain size and an extremely high bend strength (∼2 GPa), but also in limited bend ductility at room temperature. Zr additions are seen to be beneficial for three reasons. First, Zr reduces the grain size. Second, Zr getters detrimental oxygen by forming ZrO₂ particles (which in turn help to pin the grain boundaries). Third, in situ Auger analysis shows that Zr reduces the concentration of Si segregated at the grain boundaries. This is thought to enhance the grain boundary cohesive strength and thus leads to the observed ductility.