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.