Microstructure and mechanical properties of lanthanum oxide-doped Mo–12Si–8.5B(at%) alloys

Mo–12Si–8.5B alloys with different mass fraction (0, 0.6 wt%, 12 wt%) lanthanum oxide(La2O3) additive were fabricated by using arc-melting and spark plasma sintering (SPS) techniques. The doped Mo–12Si–8.5B alloys are consisted mainly of α-Mo, Mo3Si and Mo5SiB2(T2) phases. It is found that the grains are reduced and the intermetallics particles are dispersed more homogeneously after the addition of La2O3. The optimization in microstructure induces corresponding improvements in both compression strength and breaking strain of the alloys. The predominant strengthening mechanisms are fine-grain strengthening and particles dispersion strengthening. In addition, fracture toughness test shows that the addition of La2O3 can improve the toughness of Mo–12Si–8.5B alloys, for which the toughening mechanism involves crack trapping by α-Mo phases and extensive small second phase particles in the alloys.