Composition Design,Fabrication And Property Investigation Of Phase Separation And Low Thermal Expansion Cu-based Alloys

In recent years,with the continuous development of science and technology,the electronic products in the microelectronics industry are constantly developing towards a highly integrated and miniaturized direction,leadong to a sharp increase in heat production per unit area,which has put forward more stringent requirements for the performance of electronic packaging materials.Pure Cu has excellent thermal conductivity(TC)and electrical conductivity,but its thermal expansion coefficient(CTE)is very high.Due to the Invar effect,Invar alloy show a very low CTE,but its TC is very low.Therefore,the researchers have been working hard to find an effective alloy preparation method to fabricated the Cu-Invar composite materials with low CTE and high TC.Based on the thermodynamics database of two phase-separation Cu-based alloys constructed by our group,using the calculation of phase diagrams,vacuum arc melting,ultra-sound gas-atomizing,hot pressed sintering and spark plasma sintering technology,the low CTE Cu-Invar alloys were designed and fabricated.The microstructures,CTE and TC of the composites were systematically studied.The main achievements are summarized as follows:(1)Based on the calculation of phase diagrams(CALPHAD)approach and vacuum arc melting technology,the Cux(Fe0.64Ni0.32Co0.04)100-x(x=30,45,60,wt.%)series alloys were designed and prepared.The effects of annealing process on microstructures,TC and CTE were investigated in these prepared alloys.The results show that the Cu-Fe64Ni32Co4 isotropic polycrystalline alloys present two separate Fcc phases(Fec Cu-rich phase and Fcc(Fe,Ni,Co)-rich phase)microstructures after annealing at 600 ? and 800 ?.After annealing at 600 ? for 50 h,the CTE of the alloys decrease obviously and the TC have some improvements.In addition,the TC and CTE of the alloys can be effectively controlled by changing the content of Cu.(2)The Cu/Fe37Co54Cr9 based composite powers were fabricated by ultra-sound gas-atomizing.The microstructures of the powers have the typical liquid phase two phases separation characteristics,which are made up of Fcc copper-rich phase and Fcc Invar(Fe,Co,Cr)phase.Composite sintering materials with uniform microstructure and 97%density were obtained after hot pressed sintering and spark plasma sintering of composite powders.And the CTE of the materials are reduced after annealing treatment,while the TC is significantly enhanced.