The Basic Research On Synthesis And Application Of Cr₂AlC

Ternary layered compound Cr₂AlC has not only the high temperature,the high conductivity and the thermal shock performance of metals,but also possessing with the high strength,the high shear modulus,the high young's modulus,the corrosion resistance,the high temperature oxidation resistance and other performance of the ceramic,at the same time also owning comparable to graphite,MoS2 lubricating.Therefore,The Cr2AlC has a fairly broad application prospect.The Cr2AlC ceramic powder was synthesized in salt bath including BaCl2,KCl and NaCl,using Cr3C2 powder,Al powder,Cr powder as raw materials.Ihe influence of the composition of raw material,synthetic temperature and holding time to the synthetic product were invested.The results show that:The synthetic powder had more impurity phase using C powder,Cr powder,Al powder as raw material.The impurity phase number of the synthetic powder decreased significantly using Cr3C2 powder,Cr powder,Al powder as raw material.The reaction will be not sufficient when the aluminum content is insufficient,leading to more Cr3C2 phase in the synthesis powder.When excessive Al reached 30wt%,the synthesis powder contained Al₂O₃ phase.With the synthesis temperature increasing,the Al₂O₃ and Cr3C2 phase of synthesis powder decreased,but the synthesis temperature is exorbitant,can cause Cr7C3 phase in the synthesis powder.Optimum process conditions of synthesizing Cr2AlC for salt bath process:the Cr2AlC ceramic powder without impurity phase can be obtained when Synthetic conditions are Al excess 20 at%,at 970?and holding 2h with Cr₃C₂powder,Al powder,Cr powder as raw materials.With homemade high purity Cr₂AlC ceramic powder and industrial pure copper as raw material,the Cu-15wt%Cr2AlC composite material was prepared by cold pressing with vacuum sintering.The influences on the relative density and the microhardness of composite of the test pressure,sintering time and sintering temperature were discussed through orthogonal optimization,and the microstructure of composite was observed and the phase of composite was analyzed.The results show that:The Cr2AlC particles are dispersed in the Cu substrate.The Solid Sloution Strengthening Effect has happened bewteen Cr2AlC and Cu with the increasing of the sintering temperature,the sintering time,which causing constant distortion of Cr₂AlC lattice.The density of the composite is 6.78g/cm³,the relative density of the composite is 96.76%and the microhardness of the composite is 156.33 HV when using500 MPa,holding 1h,at 1000?.On the basis of orthogonal experiment,the influences on the resistivity,the thermal conductivity,the coefficient of friction,material fracture mode of composite of the pressing pressure,sintering temperature and sintering time were studied.Results show:the resistivity and friction coefficient of composites is declining,the thermal conductivity is increasing with the increasing of the pressing pressure and sintering temperature.With the extension of sintering time,the resistivity and the friction coefficient of composites is gradually reducing,the thermal conductivity is first up down later.The fracture way of the composite is rittle fracture.