Study On Method And Thermodynamic Mechanism Of Jointing/Compositing Of Immiscible Cu/Nb System

Due to their excellent properties,the joints and composites based on Cu / Nb metal systems have attracted more and more attention in the field of nuclear energy,electronic technology,aeronautics and astronautics and automobiles.However,because of the Cu/Nb system of positive enthalpy of formation,there are huge differences between the melting point,density and crystal structure,and the solid solubility is limited.The differences make them can not form any intermetallic compound or supersaturated solid solution,so it is very difficult to realize the Cu / Nb high strength connection,high strength metallurgical bonding.In this paper,a direct bonding process,especially in the non-vacuum low-pressure conditions and the contact surface is small circumstances,induced Cu/Nb inter diffusion between the ultimate realization of the rod-shaped copper / niobium high-strength connection,obtained good mechanical properties The mechanical properties of Cu/Nb thin films were investigated by means of mechanical alloying method.The results show that the Cu/Nb thin films have good conductivity and satisfy the modern non-pulsed magnetic field The high requirements of the material.Based on the above work,the main results are as follows:(1)This study provides a direct bonding method to achieve the rod-shaped metal Cu/Nb high-strength metallurgical at the non-vacuum and low-pressure conditions.The diffusion bonding of copper and niobium was successfully achieved by strictly treating the surface of rod-shaped pure copper and rod-like pure niobium with the same size and accurately controlling the bonding pressure and annealing temperature.The average connection strength has up to 222 MPa,much higher than the tensile strength of copper 175 MPa.(2)Based on the Miedema theory and Alonso theory,a thermodynamic model for the realization of the direct bonding and heat treatment of rod of Cu / Nb was established.The thermodynamics driving force of copper-niobium inter-metallic is calculated and determined by the thermodynamics model combined with differential scanning calorimetry(DSC)test,which is mainly derived from the storage energy of copper rod and niobium rod itself.(3)In this study,the nano-scale blending of different ratio of Cu/Nb powders at different micron levels was achieved by mechanical alloying.Cu/CuNb film/Cu was successfully prepared by controlling the bonding pressure,the sintering temperature and the holding time and realizing the composite of mutually insoluble metal successfully.