Fabrication Of Fiber-structured Mo-Cu Composites By Infiltration

The fiber-structured Mo-Cu composites were investigated concerning the preparationmethod, macro morphology, micro-structure, mechanical and physical properties.Molybdenum fiber was used as the raw material, which was weaved into the fibrous matsdelicately by non-woven technology. Then3D molybdenum fibrous performs wereobtained by acid treatment process and mould pressing formation, respectively. Thepreforms above were used as the substrate phase. Finally, fiber-structured Mo-Cucomposites were fabricated by pre-sintering process and infiltration, respectively. Similarly,Mo-Cu composites, which used molybdenum powder as the raw material, were preparedby the same method. The main conclusions are as follows.(1) The molybdenum fibrous preforms obtained by mould pressing formation havewider range of porosity. And the variation in molding pressure with relative density ofthem is approximately linear relationship. When the molding pressure is80MPa, therelative density reaches the maximum (84.25%). This fibrous preforms have the betterpressing feature than the conventional molybdenum powder compacts.(2) With the40MPa molding pressure, the molybdenum fibrous preforms which werepre-sintered reaches the effect of densification. With the increase of the pre-sinteringtemperature, the range of volume shrinkage rate is only from1.14%to3.15%, which alsomeets Arrhenius equation. When the pre-sintering temperature is1450℃, the relativedensity is up to the maximum (74.05%), which is3.12%higher than that of the onewithout pre-sintering. And the shrinkage rate also reaches the maximum (3.15%).(3) The molybdenum fibrous preforms which were not pre-sintered are used as liquidcopper infiltration to obtain fiber-structured Mo-Cu composites. There is dense andhomogeneous structure with fibrous character obviously in the composites. After highsintering temperature, the molybdenum fibrous preforms can maintain a certain degree ofthe porosity and hole shape, which makes content of molybdenum different in fiber-structured Mo-Cu composites. The relative density of the composites is above99%.With the increase of molding pressure, the actual and relative densities of fiber-structuredMo-Cu composites are increased, respectively. And the hardness of the composites is alsoimproved with the increase of the mass fraction of molybdenum. Meanwhile the electricalconductivity of them is dropped. When mass fraction of molybdenum is84.77%, themaximum relative density and the hardness reach99.43%and226.7HV for fiber-structuredMo-Cu composites, respectively. Meanwhile the electrical conductivity is16.5MS/m.(4) The molybdenum fibrous preforms which were pre-sintered are used as liquidcopper infiltration to obtain fiber-structured Mo-Cu composites. The microstructure of thecomposites is still fibrous character. And the interface between the Mo phase and the Cuphase maintain dense and flat, which is lower hole in the composites and Cu phases thanthat of the ones without pre-sintering. At the same time, The Cu phase is no oxidation andthe Mo phase is fewer oxidation than that of the ones without pre-sintering. With theincrease of the pre-sintering temperature, the actual and relative densities offiber-structured Mo-Cu composites are decreased, respectively. But there is not muchchange in the electrical conductivity of them. When the pre-sintering temperature is1250℃, the micro-structure, mechanical and physical properties of the fiber-structuredMo-Cu composite are the best. And the relative density, the hardness and the electricalconductivity of this composite reach99.65%,216.1HV and17.1MS/m, respectively, whichis higher than that of the one without pre-sintering.(5) When the molding pressure is40MPa and the process of pre-sintering andinfiltration is1250℃×1h,1270℃×1.5h, respectively, the micro-structure, mechanical andphysical properties of the fiber-structured Mo-Cu composite is better than that of thepowder-structured Mo-Cu composite in the same method.