Research On The Key Techniques Of Cladding Extrusion For Mg/Al Alloy

With the development of economy, the demanding for natural resources has increasingly aggravated the shortage of them. Magnesium alloys are attracting more and more attention for their abundant reserves and advanced properties, but poor plasticity at room temperature and low corrosion resistance limit their development and extensive application in industry. However, cladding extrusion maybe a good idea to resolve the two puzzles mentioned above.The method of the finite element analyze is an important method on the researching engineering. Applying the ripe finite element analyze method to the extrusion process, can analyze and study conveniently the characteristic of hot metal deformation, and are helpful to guide the technology of cladding extrusion.In this thesis, aluminum cladding magnesium alloys extruded rod were fabricated using pure aluminum and AZ31magnesium alloy at different temperatures by cladding extrusion technology. During the extrusion process, AZ31magnesium alloy was coated by aluminum. The compound, with bonding interface between aluminum and magnesium forming, was obtained. First, the numerical simulation analysis of warm plastic forming process of the typical automobile shell part under different process conditions was conducted with Deform-3D including the overall situation of the deformation, the flow of metal material in the forming process and the effect of key process parameters on forming load, then the best process parameters were determined by using the orthogonal experiment with the forming load as judging standard.After the extrusion process, the microstructure and chemical composition distribution of the cross-section of the Mg/Al extrusion alloy were investigated with metallographic microscope, scanning electron microscopy(SEM,equipped with EDS) respectively, and the micro-hardness was obtained by hardness meter. The results show that qualified products with smooth surface can be made by extrusion without obvious defects. Inter-diffusion occurs and metallurgical bond forms between A1and Mg, and an inter-metallic compound layer, with a thickness of about350um, was obtained. The magnesium-rich phase close to the side of magnesium alloy is Al12Mg17and the aluminum-rich phase close to the aluminum side is Al3Mg2. The micro-hardness test results show that the hardness of Mg-Al bonding interface can be up to200HV or more, which means the interfacial inter-metallic compounds may be generated by brittle phases.