Fabrication And Properties Of Novel Functional W-Cu Materials

W-Cu composite materials are widely used in electrical and electronics, military and energy fields because of its high electrical conductivity, thermal conductivity, excellent mechanical property and corrosion resistance, etc. With the development of high technology, higher performance requirements were raised gradually for W-Cu materials, and in some case, W-Cu materials with special structure were also needed. Therefore, in recent years, the explorement of the preparation of ultrafine grain, full density, high performance W-Cu materials and special structure of W-Cu materials, and to carry out its application evaluation, become a hot spot in the field of W-Cu materials. Conventional compression forming method and tape calendaring method were explored to prepare W-Cu materials with graded structure which is the center of this thesis. At the same time, the effect of Sc2O3 addition on the microstructure and property of W-Cu materials was also studied. Preliminary exploration was carried on for the development of novel functional W-Cu materials in this thesis.The main results obtained in this dissertation are listed as followings:With tungsten powders and copper powders as raw materials, W-Cu powder mixes with different Cu contents(W-15%Cu,W-35%Cu,W-55%Cu, weight fraction) were prepared by mechanical mixing. The powder mixes were filled in a die and compacted layer-by-layer. The green compacts were then sintered in H2 atmosphere to obtain sintered W-Cu samples. Microstructure and property of the sintered samples were tested. The results indicate that the sintering temperature has obvious influence on the microstructure and properties. The W-Cu samples sintered at 1150℃ also have layered distribution of W(Cu) gradients in the structure, and the layers have good combination. The relative density and thermal conductivity of the samples sintered at 1150℃ are up to 95% and 142W/(m·K), respectively. Vickers hardness is around the range of 249-308HV, and bending strength is around the range of 514-669MPa.For preparing graded W-Cu samples with large area, with tungsten powders and copper powders as raw materials and PVB as the binder, W-Cu green tapes with different Cu contents (W-25%Cu,W-50%Cu,W-75%Cu, weight fraction) were prepared by a tape calendaring method. W-Cu graded green tapes were obtained by laminating the three W-Cu tapes together, and were subsequently sintered in H2 atmosphere to obtain the graded W-Cu samples. The results indicate that W-Cu samples with layered distribution of W(Cu) can be successfully fabricated by the tape calendaring and lamination process. The layered samples have good microstructure and properties with controlled shape and size. The binder content has an obvious effect on the density and properties of the W-Cu graded materials, and the green tapes with 6% binder show good formability and high density of up to 93.11% and thermal conductivity of up to 148W/(m·K) can be achieved for the graded W-Cu samples sintered at 1150℃, and the Vickers hardness is around the range of 294-345HV, and bending strength is around the range of 574.8-725.6MPa.With (NH4)6H2W12040, Cu(NO3)2·3H2O and Sc2O3 as raw materials, ultrafine W-20Cu composite powder with different Sc2O3 additon (0-0.7wt%) was prepared by the gel-coreduction process. The powders were compacted and sintered at 1250℃ in H2 to obtain Sc2O3/W-20Cu composite materials. The sintered samples have relative density up to 97% with uniform microstructure, and electric conductivity is higher than 37%(IACS%), Vickers hardness and bending strength are up to 265HV and 910MPa, respectively. It was found that suitable amount of Sc2O3 addition has no obvious influence on microstructure, density and electric conductivity of the W-Cu materials, but, could effectively improve the mechanical properties of the composites. The microhardness of W-Cu composites doped with 0.5% Sc2O3 increase by 13.58%, and the bending strength of W-Cu composites doped with 0.3% Sc2O3 increase by 7.70%.