Preparation And Plastic Deformation Research Of Nb Based Composites Reinforced By SiC

The rapid development of the aerospace industry spawns high temperaturestructural materials, and requires the material not only can withstand very hightemperature, but also have higher strength. In recent years, refractory metal niobiumgets more and more attention of people because of high melting point and low density,but low room temperature strength limits its application range. At present, niobiumbase reinforced composite materials have been studied further by scholars at home andabroad, but the enhanced materials tend to have higher density. Silicon carbide isceramic materials with low density, and it is expected to prepare a new generation ofhigh temperature structural materials by adding silicon carbide ceramic to metalniobium. At the same time, we study the high temperature deformation law of thesematerials to promote the material to be applied in engineering.We selected the ultrafine silicon carbide ceramic powder as enhancement phase ofthe metal niobium in this article and added3%、5%、7%mole fraction of the siliconcarbide powder. We adopted the mechanical ball grinding to prepare compositepowders, and analyzed microstructure change rule of composite powder in this process.We got Nb block composite material by vacuum hot-pressing sintering technology andanalyzed microstructure and mechanical properties of the three different componentsof block composite material at room temperature, studied their high temperaturecompression deformation behavior and microstructure after deformation by hightemperature compression deformation experiment.It showed that the ball mill speed and ball milling time would affect the powdermorphology changes in the process of ball milling by the research of mechanical ballgrinding process in Nb/SiC composite powder system. If we adopted smaller speed,powder could not be fully refined, and if we adopted longer ball grinding time, thepowder particle size distribution no longer changed with the extension of time whenthe powder reached its limit size, and it would introduce impurities if ball milling timewas too long.We got Nb block composite material with97.6%density by adopting vacuum hotpressed sintering method, in the condition of thermal insulation60min for under1550℃. Composite materials was composed of niobium substrates, Nb3Si and Nb2C phase by XRD, and microstructure was composed of equiaxed grains with less than10μm by SEM. Room temperature fracture strength、hardness and compressionstrength of three kinds of material increased along with the increase of silicon carbidecontent, fracture toughness at room temperature reduced because of the less of niobiumsubstrates. At room temperature materials showed transgranular cleavage fracturecharacteristics by observing morphology of the fracture surface in these materials. Athigh temperature, compression strength at the same temperature (1050℃、1100℃、1150℃)increased along with the increase of content of silicon carbide, and themicrostructure after high temperature compression showed signs of the intergranularfracture. It showed that the fracture mechanism of materials had changed fromtransgranular cleavage fracture at the room temperature into intergranular fracture athigh temperature.