| With the development of modern science and technology, a single material can not meet human’s needs. Composite materials arise at the historic moment. Composite materials have a wide variety, and laminar composite metal is one of the hotest topics in the study of material science. Aluminum has the advantages of high strength ratio, good plasticity, good corrosion resistance, good electric conductivity and thermal conductivity, light weight and low price and so on, stainless steel has the advantages of high strength, corrosion resistance, easy machining and the surface gloss, the composite connection to the aluminum and steel structure, has produces huge social benefit and economic benefit. But, as a result of great differences in physical and chemical properties between iron and aluminum, which cause the great welding difficulties directly, so the study on the diffusion welded interface of steel and aluminum has a practical significance.The composite sample of the304stainless steel/Al/304stainless steel (304SS/Al/304SS) was prepared by the diffusion welding in the vacuum using commercially pure aluminum as a transition zone. The chemical composition, interface microstructure, fracture morphology and phases were measured by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD). The shear strength and microhardness near the interface were tested by shear and microhardness tests. The influences of different diffused processes on element distribution, microstructure and properties of interface have been analyzed.The results of microstructure analysis show that stainless steel/aluminum can achieve combination by the diffusion welding in the vacuum. Interface component analysis shows that at the range of the study temperatures, the atomic interdiffusion phenomenon was founded near the interface. Every kind of the element reduced gradually with the increasing of the diffusion distance, and formed the different transition layer with the different concentrations in the diffusion zone. The thickness of transition zone increases with the rising diffusion temperature and the extending the holding time.At500～600℃, the interface of304stainless steel-aluminum formed Fe2Al5, Fe4Al13and Al5FeNi phase, with the diffusion temperature increasing to700℃, a lot of FeAl2and Al3Ni phase were found near the interface except Fe2Al5, Fe4Al13and Al5FeNi phase with the aluminum liquid, and the fracture of composite sample belongs to the typical cleavage brittle fracture.Hardness tests and shear tests show that because the elements interdiffusion and the intermetallic compounds (Fe-Al) were formed in the interface, so the maximummicrohardness and the position of fracture were appeared in this interface. The shear strength of the interface decreases with the rising heating temperature at the range of the study temperatures, and it first increases and then decreases with the extension of the holding time. |
