| Ternary layered ceramic Ti2SnC has excellent electric conductivity, stable thermal performance and high elastic modulus, layered structure endows it the self-lubrication.As a kind of potential reinforced phase of copper matrix composite,it causes a great attention.The existing related research shows that when Ti2SnC is with small particle size and low volume fraction in copper matrix composite, its reinforced effect is limited, so the author adds a second reinforced phase NbSe2 to improve the comprehensive performance of the composite, NbSe2 has a hexagon lamellar structure as a new type of solid lubricant with good electrical conductivity and lubricating, the structure makes it good dispersibility in composite and it will have a further strengthening on the copper matrix composite.First,the Ti2SnC and NbSe2 are prepared,then the Cu-Ti2SnC-NbSe2 composite is prepared by powder metallurgy method. The various properties of copper matrix composite with different ratio enhancement phase are studied to determine the optimal proportion.Cu-Ti2SnC-NbSe2 composite should be with good strength, hardness, electrical conductivity,friction and wear property, it mainly used as a kind of electric contact material.In this paper, first of all, the preparation of Ti2SnC is studied with different sintering temperature, holding time and sample made pressure,and the planetary ball milling is used to further refined Ti2SnC powder particle size,then the powder particle size distribution is researched through laser particle size analysis. The Nb-Se powder is encapsulated into quartz tube with vacuum environment,and it is heated to 780℃ holding1 h to prepare the hexagon lamellar structure NbSe2 powder.The powder particle size is researched by laser particle size analysis.The different volume ratio of Cu-Ti2SnC-NbSe2 powder is mixed by ball milling, and the composite is prepared by hot-pressing sintering with different process conditions.The physical phase composition and microstructure of the composite are analyzed by optical metallographic microscope,SEM, EDS and XRD. The physical and mechanical properties of composite are tested,including relative density, microhardness,coefficient of friction,conductivity and tensile strength after hot rolling. The influence law of sintering process parameters and different composition on the properties of composite is studied.The results show that:(1) The high purity Ti2SnC is prepared with Ti-Sn-C reaction system in the 1200℃, Sn is both reactant and product.When the sample made pressure increased to 70MPa, reaction at 1175℃ with 1h or at 1200℃ with 0.5h both generate high purity Ti2SnC powder. The powder will get the best refinement effect through planetary ball milling with 300 r/min,0.75 h. Laser particle size analysis shows that the average particle size of Ti2SnC powder is 0.790μm,and the NbSe2 powder is 7.495μm.(2)The copper matrix composite is prepared by hot pressing sintering with Cu-Ti2SnC-NbSe2 powder. The sintering temperature is 850℃ according the nature of two reinforced phases. Taking A5 powder as an example, the composite is prepared in 850℃ under different heat preservation time.The test results of relative density, microhardness and electrical conductivity show that the best heat preservation time is 2 h, under the heat preservation time the composite has a good comprehensive performance.Then the composite is prepared with Al-A9 mixed powders by hot-pressing sintering:850℃,50 MPa,and heat preservation time 2h.(3)The relative density, microhardness, friction coefficient,electrical conductivity and tensile strength after hot rolling are tested.The experimental results show that the enhancement effect of two enhancement phases is better than single one. when the volume fraction of Ti2SnC is 7%, the volume fraction of NbSe2 is 3%,the material has the best comprehensive performance. |
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