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

摘要

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 (La_2O_3) 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, Mo_3Si and Mo_5SiB_2 (T2) phases. It is found that addition ofLa_2O_3 has little effect on both the grains and intermetallic sizes. The intermetallic particles are more homogeneously dispersed within α-Mo matrix by increasing the La_2O_3 content. Compression test and three-point bending test showed that both compression and flexure strength of alloys were obviously improved by the addition of La_2O_3. 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 ? m~(1/2) that revealed the addition of La_2O_3 had little effect on improving the alloys toughness.