| More application of magnesiμm alloys has become a development direction for the future.But magnesiμm is the hexagonal structure,has limited slip systems.It has poor forming ability under room temperature condition.Therefore improving its ability to plastic deformation becomes an urgent problem to solve very critical.It is proved that small equiaxed granis can improve its ability to plastic deformation. So, to find a process to refine the effective grain size of magnesiμm alloy is very important.The purpose of this paper is to investigate the microstructure evolution, mechanical properties of AZ31 magnesiμm alloy by mixed deformation and give acomparative analysis. Focused on mixed deformation mechanism of grain refinement and model,compresed properties at room temperature after deformation and fracture mechanisms and squeeze pressure and strain. In order to squeeze in the comparative analysis of two-step to get on the AZ31 magnesiμm alloy and the deformation mechanism of deformation process itself and of a preliminary study.In this paper, as-casted AZ31 magnesiμm alloy were elected as mixed deformation material for investigation. The AZ31 magnesiμm alloy microstructure and texture evolution were analyzed by Optical microscopy (OM), and X-ray diffraction; the mechanical properties and fracture way and mechanism were discussed by mechanical test at room temperature, the grain refinement mechanism were explored by transmission electron microscopy (TEM), the properties and microstructure of annealing after mixed were discussed , and the extrusion force and distribution of stress and strain during mixed process were simulated by finite element analysis. After two steps of the AZ31 magnesium alloy after deformation respectively, were annealed and Comparative Analysis. And discussed the thermal stability.The main results can be summarized as follows:After one step of CCAE,significant grain refinement of magnesiμm alloys can be observed. The ductility, strength and microhardness were improved with the grain refinement, which is consistent with Hall-Petch relationship. The effect of grain refinement was improved with lowering the CCAE temperature. Grains of AZ31 magnesium alloy decreased with the deformation temperature decreases under the temperature range of 250~400℃. Both the ductility and synthetic mechanical properties of AZ31 magnesium alloy can be improved by CCAE. The sample after one step of CCAE were squeezed with one step of ECAE under A path.The thick tissue were significantly reduced and further refined grains were got.After ECAE,the grain size up to 3μm. The ductility, strength and microhardness were further improved with the grain refinement. Both the ductility and synthetic mechanical properties of AZ31 magnesium alloy can be further improved by ECAE.After CCAE at 250℃,the compressive strength reached to 407MPa,the compression ratio up to 16.5%;After the 300℃ECAE(300℃,CCAE),the compressive strength reached to 416MPa, the compression ratio up to 15.9%.Refinement mechanism is basically the same of CCAE and ECAE,.Grain refinement mechanism of AZ31 alloy during them can both be described as grain fragmentation in the shear zone and extrusion ratio zone for continuous dynamic recovery and recrystallization (CDRR). For the CDRR, at the initial stage of deformation, dislocation density increases and then dislocations are arranged into dislocation boundaries and sub-grain boundaries. With further deformation, these sub-boundaries evolve to low angle grain boundaries (LAGBs) and high angle grain boundaries (HAGBs), therefore the grains can be refined.
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