Interface Characterization And Properties Of Copper-titanium Composite Plate Produced By Explosive Bonding

In order to economize the precious rare metal materials, and combine their physical, chemical and mechanical properties fully, explosive welding has been widely used due to its unique advantages in the bonding of the dissimilar materials. The interface of explosive composite materials is different from the base metal in composition, microstructure and properties, so explosive composite materials have their own unique and important performances. A large area of the similar or dissimilar metal plate can be connected instantly so as to achieve a strong metallurgical bonding. Usually, it is used to prepare thick composite plate with distinct difference of physical and chemical properties. Nowadays, the copper-titanium composites by explosive welding are replacing the traditional coating titanium anode with an improved conductivity of titanium electrodes, and improved corrosion resistance of the copper. Therefore, this technology provides a great favor in the chlor-alkali industry.Researches about explosive composite mostly concentrate in the explosive parameters and the process of composite deformation, but with lack of analysis in the microstructure characterization of the bonding regions. Thus, a large copper-titanium explosive composite plate provided by a large enterprise is chosen as the research object. The optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction were used to analyze the morphology, structure, composition and other characteristics of the interfacial zone of composite, as well, to study systematically the formation of the waveform and evolution process、plastic deformation、melting and diffusion behavior and other physical metallurgies in interfacial regions. The results show that:Currently, the mechanics during explosive welding has already been studied for a long time. However, the microstructure of the bonding region still needs systematic analysis. The experiment results in this paper based on the production of copper-titanium by explosive welding will provide an academic guidance for industry and promote the production of explosive welding. Then the investigation on waveform, plastic deformation, melting and diffusion in interfacial region has been conducted. The results show that:(1) During explosive welding process, plastic deformation occurs near the interface under the high speed impact of clad sheet. The deformation mainly focuses on the vortex in front of explosive wave.(2) A few of molten metal exists before the explosive wave in smooth interface between copper and titanium metal. The whirlpool has a complex composition, consisting of not only the melt but a large number of metal fragments.(3) Due to the occurrence of atomic inter-diffusion, excellent metallurgical is formed in the copper-titanium interface. The diffusion of the nearby atoms is influenced by several factors including temperature, concentration, plastic deformation and melting, etc.(4) The effect of heat treatment on the interfacial microstructure and composition of composite is much significant. As the heat treatment temperature increases, the grains of bonding region gradually grow. A variety of intermetallic compounds generate with the diffusion of copper and titanium element.In this paper, electrochemical analyzer, mechanical tester and microhardness tester were used to analyze the electrochemical properties, fracture and microhardness features of the copper-titanium interface. In addition, the effect of the interfacial characteristics on the performance of the composite plate is clarified. The results are listed here:(1) The electrical conductivity of the composite material is superior to the pure titanium and the corrosion resistance is between that of pure copper and pure titanium.(2) Interfacial fracture analysis shows that at a relatively low temperature, fracture is a mixed brittle and ductile mode, whereas at high temperature, only brittle fracture mode is found.(3) The distribution of microhardness in the bonding area shows that appropriate heat treatment can at a great extent eliminate the deformation hardening caused in explosive welding.Summarily, the interface of explosive welded copper-titanium exists a comprehensive phenomenon consisting of the four interrelated processes as above. Importantly, each process contributes to the metallurgical bonding.