The Study On Atomic Interaction In Solid-phase Binding Region Of Bimetallic Cold Welding

The study of the mechanism of binding metal welding is still based on the fusion welding, in this thesis, by using experimental method to discussing the problems arising in the metal deformation work and atomic interaction of metal binding interface, further explained the solid phase interface connecting mechanism of Cold welding. Based on the test results of Non-fusion welding, to studying the physical substance of atomic binding by metal welding, it can not only enrich the material connection theoretical research, but also provide a theoretical basis for the development of non-fusion welding material solid connection method.From the experiment of Al/Cu、Cu/Zn cold welding, the connection interface are closely together, the line scan showed that in the cold connection interface exist obvious atomic elements transition, so that increased the contact with each other to promote the combination of atoms, the material closer connections. The Al/Cu joints in the TEM microstructure shows the original grains are elongated and the atoms are broken at the interface, Al, Cu broken crystal doped mutual snap together to form the combination of atoms.During the Cold welding, elastic deformation and plastic deformation are happened in the mental, by the stress- strain curve law, use deformation work method to find the relevant calculations of metal deformation work, the elastic portion is relatively small compared with plastic deformation, so it can be ignored. First, metal deformation is relatively easy, with the force increasing, the interface lattice distortion becomes large, inside the metal the dislocation proliferation and generating interaction, leading to hardening, metal deformation resistance increases, the deformation can increase the rate of speed. As the deformation continues, the enhanced role of dislocations cancel each other, deformation work continues to increase, but the rate of increase slowed. Deformation of the metal provides the energy basis of bonding metal atom, by the experiment and calculation results, due to the severe plastic deformation, metal broken crystal doped with each other, atoms contact with each other, enabling the connection of the metal.when the atoms reach the interatomic distance, The per polycrystal interface binding energy of Al, Cu are 3.19J/m2, 7.08J/m2 in unite area, The polycrystal interface binding energy of Al/Cu、Al/Fe are 4.78J/m2, 5.02J/m2. The most stable face of Face-centered cubic metal is Al(111)/Cu(111), Interface spacing played an important role in the stability of the interfacial bonding.In the Cold welding process, The external force do work not fully used to deformation of materials, the interface binding energy can be relatively small, the deformation work accounts for a relatively small percentage of external force work because of the internal material defects will hinder the further deformation, and need greater external force to make the material deformation, to achieve the atoms binding. The energy have three grade because of the surface irregularity dislocations, plastic flow, thermal effects and other factors effects the combination of atoms, explained the interface connection mechanism of welding at room temperature.