Numerical Simulation Study On Solid-state Recycling Process Of Magnesium Alloy

As the lightest structural metal material, Magnesium alloys which are compared as the "21st Century Green Engineering Material" have broad development prospects in the automotive, aerospace and electronic industry. With the rapid development of magnesium and magnesium alloy industry, large amounts of magnesium alloy scrap will be produced, so to solving the problem of recycling of magnesium alloy scrap is imminent, which has become the major factor of the sustainable development of magnesium alloy industry.First, elementary performance, characteristics and applications of the magnesium alloy, present situation of magnesium alloy scrap and recycling technology of magnesium alloy scrap are summarized. The extrusion process of the magnesium alloy is studied according to the metal plastic theory, and finding the rule of extrusion parameter.In this study, Gleeble-1500D thermal simulator was used to the isothermal compression tests of the AZ91D magnesium alloy. It showns that the flow stress behavior of AZ91D magnesium alloy is content with Hyperbolic sine function. Through this analysis we can get the flow stress function of AZ91D magnesium alloy: (ε|·)=3.21227×10¹⁴[sinh(0.00866σ)]⁷⁸⁵exp(-176010/RT)The effects of the extrusion process parameters, such as deformation temperature, extrusion velocity and extrusion ratio on the extrusion process were studied by the DEFORM-3D software. These results of AZ91D and AZ31 magnesium alloy extrusion processing numerical simulation show that the temperature, strain and stress in the radial, axial were unevenly distributed and the maximum value of the temperature and strain appears at the die exit. In the extrusion process, the extrusion pressure increases fastly at the beginning period, when the semifinished product was extruded from the concave model, the extrusion pressure reaches maximum value. Then, the extrusion process becomes steady-state, the extrusion pressure is reduced slowly and remains stable basicly.The simulation results show that: the temperature of the material at mould mouth and extrusion pressure increase with the increasing of the extrusion speed. when the other parameters are invariable; When the extrusion speed and extrusion ratio are certain, the temperature of the material at mould mouth increases with the increasing of initial heating temperature, extrusion pressure decreases with the increasing of initial heating temperature; When the extrusion speed and initial heating temperature are certain, the temperature of the material at mould mouth and extrusion pressure along with the increasing of extrusion ratio. Under the comprehensive consideration, we should choose the extrusion speed of 0.5 mm/s, the semifinished product initial heating temperature of 400℃(AZ91D) and 350℃(AZ31), the extrusion ratio of 25:1.