Study On Clad Extrusion Of Magnesium

Mg alloys are attracting more and more attention for their high specific strength, highspecific modulus, good electromagnetic radiation absorption and abundant reserves. Inparticular, with the energy depletion, environmental pollution and other issues to be resolved,the research and development of magnesium alloy is also one of the hotspots of the worldtoday.In this thesis, clad extrusion developed AZ31magnesium alloy tubes with5083aluminum or copper. In this paper, the cast magnesium alloy homogenization annealingprocess, magnesium alloy extrusion process, magnesium alloy-aluminum alloy andmagnesium alloy-pure copper clad extrusion process and the principles of clad extrusioninterface were studied. The main research content and experimental results are as follows.Organization of AZ31magnesium alloy has a great influence on the extrusionperformance.By homogenization treatment, dendrite segregation of magnesium alloy ingothave been eliminated. The optimized temperature and time for AZ31alloy ingots in this studyare390℃×16h.At380°C, when the extrusion ratio is23, the pipe AZ31magnesium alloy has a denserecrystallized microstructure and good mechanical properties. If extrusion ratio is too small,grain crushing effect is not obvious, part of the grain is not dynamic recrystallization, on theother hand, larger extrusion ratio can lead to grain growth and banded structure.Tensile fracture characteristics of as-cast AZ31magnesium alloy is cleavage fracture,after homogenization annealing by390℃×16h, the second phase Mg17Al12fully dissolvedinto the matrix, so the number of dimples increases. Tensile fracture characteristics ofextruded AZ31magnesium alloy is quasi-cleavage, and with the extrusionratio increases, the cleavage plane and the torn edges are reduced.Through using DFRORM-3D software to carry out extrusion simulation, when extrusionspeed is1mm/s, billet temperature is380℃, mold temperature is360℃, extrusion ratio is23,extrusion cladding pipe in good condition. The extrusion stress, strain and strain ratesimulation curve display extrusion process parameter is reasonable.Through the experiment, the accuracy and dependability of the hot clad Extrusion’ssimulation has been verified in the thesis. When the extrusion ratio is23, extrusion process inthis article can get high-quality aluminum-magnesium and copper-magnesium composite tube,and interface is linked closely together. If the extrusion rate is increased, then the surfacequality decline. Interface Binding Strength of Aluminum alloy and magnesium alloy firstincreases, then decreases. When the extrusion ratio is23, interface of Aluminum alloy and magnesium alloy is fairly good, and interface bonding strength is greater than the magnesiumalloy and copper.The interface of aluminum and magnesium is wide and thick, by regional energyspectrum scanning and Mg-Al two ternary phase diagrams, it can be judged that surface layeris Al3Mg2. Elements mutual diffusion of Mg and Cu is not obvious; the diffusion layer is thin,which belongs to the solid phase diffusion. There is no obvious element diffusion in on bothsides of the interface. Although the temperature is high, the extrusion process fast.