Nano Mo–La–O particles strengthened Mo alloys fabricated via freeze-drying technology and low temperature sintering

Abstract

This work proposed an innovative technology to fabricate Mo–La–O nanoparticles strengthened Mo alloys with ultrafine nano grains via freeze-drying and low temperature sintering. These novel nano Mo–La–O particles including La7Mo7O30, La5Mo3O16, La6Mo2O15, La5Mo4O12, La4Mo2O11 and La2(MoO6) remain coherent or semi-coherent interfaces with Mo matrix to strengthen their phase boundaries. Moreover, nano Mo–La–O particles enriched in excess oxygen absorb nearby impurity oxygen and then lead to the purification of Mo matrix. Furthermore, the low temperature sintered Mo–LaxMoyOz alloys possess high relative density (98.1%), which is due to the high sintering activities of ultrafine powders (56 nm). Comparing with available literature which involves oxide-dispersion-strengthened-molybdenum alloys (ODS-Mo), the freeze-dried Mo–LaxMoyOz alloys in our work possess the finest grain size (440 nm), the finest oxide particle size (mainly <5 nm), the highest hardness (495 HV0.2) and high strength (1201 MPa) at 30% deformation.