| With the rapid development of science and industrial technology,modern industry has put forward higher requirements for materials.Besides,connection with metal can not meet various needs of practical application,it is necessary to connect dissimilar metals.Copper and aluminum are common conductive materials in electrical industry.In the process of power generation,transmission,transformer and distribution,copper and aluminum need to be connected to achieve the transmission of electrical energy.The traditional methods,such as rolling and casting,have low yield,poor bonding performance and high cost for preparing composites,but the solid-liquid connection method for preparing copper-aluminum joint can save time and cost without being limited by size.On this basis,the metallurgical combination of copper and aluminum is realized by the solid-liquid transient connection method,and carried out heat treatment.Meanwhile,the growth rhythm of intermetallic compound(IMC)on copper-aluminum bonding interface was studied.First of all,copper-aluminum composite was prepared at different temperatures and time;secondly,the heat treatment was carried out on the prepared composite at different temperatures and holding times,so as to study the influence of heat treatment on the morphology as well as mechanical properties of composite interface.Finally,the study was performance on growth mechanism of interface IMC and the bonding mechanism of bimetallics in method of solid-liquid combination mode,some results as follows:(1)The microstructure and properties of the copper-aluminum interconnected interface prepared by the solid-liquid instantaneous connection method at different temperatures were studied.The copper-aluminum interface cracks at 550 ℃ and the IMC compound band is formed at 700 ℃.The interface combination under transient heating at 650 ℃ is smooth and flat with no obvious inclusions.No large amount of element diffusion emerged in aluminum or cooper element;and the shear strength of composite material is about 32 MPa,which is much lower than that of copper and aluminum.(2)The copper-aluminum joints are heat treated at different temperatures and times,and the microstructure and properties of composites have changed significantly.At the same temperature,the transition layer gradually broadens with the increase of holding time with the generation of solid solution as well as IMC compound,and the shear strength also decreases accordingly;when the holding time is fixed,the width of transition layer obviously increases with temperature rise,and the shear strength increases before decreasing with temperature rise.The copper-aluminum joints prepared under the heat treatment at 300 ℃/30 min after transient heating at 650 ℃ shows the best performance with 89 MPa of shear strength and 50 μm of transition layer width.(3)To further explore the solid-liquid transient connection mechanism of copper-aluminum,the mechanisms of transient copper-aluminum solid-liquid coupling mainly include diffusion and chemical reaction,of which the chemical reaction plays leading role;the interface is grown in a layer-like manner.Meanwhile,χ[Al(Cu)]and a[Cu(Al)]solid solution,along with IMC compounds of Cu9Al4,Cu3Al2,CuAl and CuAl2,are formed on both sides of matrix;there is also(aAl + CuAl2)eutectic structure at interface.(4)The fracture modes of copper-aluminum joints at different heat treatment temperatures were studied,at 200 ℃ and 400 ℃ is cleaved cleavage,and the fracture mode is quasi-cleavage fracture at 300 ℃.The fracture of composites is mainly due to the formation of hard and brittle intermetallic compounds at the interface.Most fractures occured in the brittle phase. |
