Effects of lanthanum oxide content on mechanical properties of mechanical alloying Mo–12Si–8.5B (at.%) alloys

•The Mo–12Si–8.5B alloys are fabricated by mechanical alloying technique.•The added La2O3 can refine the grain size and the intermetallic particles.•Both the compression and flexure strength are increased with the doping of La2O3.

Mo–12Si–8.5B alloys with different mass fraction (0 wt.%, 0.3 wt.%, 0.9 wt.%, 1.5 wt.%, 2.5 wt.%) lanthanum oxide (La2O3) additive were fabricate by using mechanical alloying and hot pressing sintering techniques. XRD results indicate that the doped Mo–12Si–8.5B alloys are consisted mainly of α-Mo, Mo3Si and Mo5SiB2 (T2) phases. It is found that addition of La2O3 has little effect on both the grains and intermetallic sizes. The intermetallic particles are more homogeneously dispersed within α-Mo matrix by increasing the La2O3 content. Compression test and three-point bending test showed that both compression and flexure strength of alloys were obviously improved by the addition of La2O3. The predominant strengthening mechanisms are fine-grain strengthening and particles dispersion strengthening. In addition, fracture toughness tests showed that the fracture toughness values of all alloys were on the order of 9 MPa·m1/2 that revealed the addition of La2O3 had little effect on improving the alloys toughness.