Deep Drawing Behavior And Interfacial Structure Evolution Of Al/Mg/Al Composite Sheets

Due to its weak deformation ability and poor corrosion resistance, the wideapplication of magnesium alloy is limited. Aluminium alloy has excellentductility and corrosion resistance. In this paper, magnesium alloy andaluminium alloy were formed as Al/Mg/Al multilayer composite sheet bycladding both sides of magnesium alloy with aluminium alloy via hot rollingprocess, as a result the corrosion resistance and deformation ability ofmagnesium alloy had been improved significantly, and the aluminium alloycoating can reduce the initiation and propagation of cracks as well.This paper focuses on the Al/Mg/Al composite sheets fabricated viafour-pass hot rolling method. Primarily, uniaxial tension experiment at warmstate was conducted on the composite sheets, so as to study the deformationbehavior and fracture mechanism at varied temperature and strain rate. Theresults can be summarized as follows: Firstly, the peak stress of the composite sheets decreased with the increasing of the deformation temperature anddecreasing of the strain rate, and a lot of dimples appeared at the fracture ofAZ31. Secondly, the strain rate sensitivity of Al/Mg/Al composite sheetsdecreased with the increasing of deformation temperature from150°C to200°C. Thirdly, the peeling phenomenon appeared at the deformationtemperature of150°C. Whereas the main fracture mechanism was ductilefracture mechanism with a favorable bonding properties at200°C and250°C.Subsequently, the drawn cups with maximum drawing radio atdeformation temperature of150°C,180°C,200°C and230°C have beenstudied and thickness distribution of the drawn cup have been measured bymicrometer along the rolling direction (RD),45°and transverse directions(TD). The results showed that the thickness strain distributions of the cupdrawn at150°C and180°C were approximately the same, so there was noserious earing appearing. The thickness strain distribution of the cup drawn at200°C and230°C temperature along TD were significantly lower than thosealong RD and45°directions, showing obvious anisotropy. As the deformationtemperature increased, the fracture field changed from the punch corner regionto the force-transferring area.The scanning electron microscope experiment was used to study theinterdiffusion layer structure evolution of Al/Mg/Al composite sheets duringdeep drawing. Furthermore, the bottom region, corner region and wall regionof the cup in RD and TD drawn at150°C and200°C were investigated. The results showed that the composite sheets had a favorable bonding propertieswhen drawing at200°C with the punch temperature of50°C, punch speed of15mm/min and die curvature radio of10mm, and less cracks appeared withinthe interdiffusion layer at the wall region, corner region and bottom region.However, a lot of cracks appeared obviously at the wall region and cornerregion at150°C, which means that the composite sheets during deep drawingat150°C cannot come up to the plastic deformation requirement.