Study On Preparation Technology And Properties Of RE Molybdenum Alloys

In this paper, rare earth molybdenum alloy is the research object. The rare earth molybdenum alloys doped with a trace of different La2O3or Y2O3contents had been prepared by powder metallurgy method(P/M),then they were processed by hot deformation swaging in order to improve molybdenum alloy material density and control grain size.The influence of rare earth oxide on microstructure and properties of Mo alloys and plastic deformation was analysed,and the effect mechanism was explored.The core of this thesis was using powder metallurgy method for preparation of the rare earth molybdenum alloys. Through continuous improvement of the preparation process, master the appropriate process parameters, explore the optimal preparation of the rare earth molybdenum alloys process.The sintering process,the dopeing with rare earth oxide process, and thermal deformation process on the organizational structure and mechanical properties at room temperature of the molybdenum alloys were systematic studied, its mechanism of action and impact factor were analyzed. Electronic universal testing machine was tested the rare earth molybdenum alloys’ tensile strength,bending strength and yield strength. The scanning electron microscope was used to observe the rare earth molybdenum alloys’ microstructure and fracture morphology. Consolidated results of doped rare earth oxides to improve the microscopic mechanism of the molybdenum alloys’ strength and toughness were preliminary studied.The results showed that the molybdenum alloys sintered density increased with the sintering temperature.When the temperature was higher than1950℃,the density increasing was not obvious.And then sintered density increased with increasing sintering time,when sintering time was greater than2h,sintered density changed little.The optimize sintering process was that the sintering temperature was1950℃and sintering time was2h.After adding a trace of rare earth oxides, Y2O3and La2O3particles with spherical or axial form of existence were mainly distributed in the grain boundary.They could effectively inhibit the molybdenum alloys grain size,and made grain size distribution to be moreuniform. With the content of rare earth oxide increasing, molybdenum alloys’density showed the decreasing trend after the first raising.The molybdenum alloys’fracture mode changed into a mixed fracture mode that it contains a small amount of transgranular fracture from completely brittle fracture along the grain.The best swaging holding temperature was1400℃.Molybdenum alloy grains were tensiled along the deformation direction. With the increase of the deformation, the grains become fibrosis and the grain boundary staggered combination. After the hot deformation processing, Fine grain Toughening and the second phase particles toughening were effecr on the doped molybdenum alloy, not only the strength but also toughness can be improved. Deformation was about60%of Mo-1.0La,its density was greater than or equal to10g/cm3,and the relative density reached98%. Mo-1.0La’s bending strength was1231.9MPa,its twice than not swaging.