| Magnesium alloy is the lightest of the current industrial applications of engineering materials, crystal structureis close-packed hexagonal structur and relatively low plasticity at room temperature and low temperature. Grain refinement is a good way in order to improve the mechanical properties of magnesium alloys. In recent years, there is an increasing emphasis on national researchers about ECAP technology, although this approach can obtain ub-micron or nano-level ultra-fine grain structure for aluminum, copper alloy, carbon steel, etc, it is used relatively small in close-packed hexagonal structure. This paper mainly studies microstructure and properties of mechanical in the different ECAP process parameters on AZ31 magnesium alloy and presents a more reasonable deformation mechanism of magnesium alloy through researching the organization of the deformation in the process of evolution.The author conclude influence of properties of magnesium alloy in the various process parameters through AZ31 magnesium alloy microstructure and mechanical properties of research and testing in different squeezed paths, pass, temperature, mold corner and other process parameters. The results show that there is a good effect of grain refinement and grain size distribution is relatively uniform in Bc path; The magnesium alloy grain size gradually reduced with deformation pass increased, stabilizing grain size in six pass, the average grain size is about 2.1μm; The lower the deformation temperature is, the smaller dynamic recrystallization grain size is, the better grain refinement is; The macro-hardness specimen with deformation times, have significantly improved, macro-hardness value reached the maximum 90.81MPa after three pass, then the hardness decreased slightly stabilized. the yield strength and tensile strength of magnesium alloy gradually decreased, elongation continued to increase with deformation pass increased; The tensile fracture toughness is nest, as the dimple size decreases with fine grain, the growing number of dimples.Organization variation with ECAP deformation indacate that degrees of grain refinement is different near the corner of the inside and outside corner in the specimen cross-section, the level of grain refinement is more obvious in the corner of the inside, it cause organization very uneven uniformity, as the deformation pass increased, the grain size gradually reduced, the organization tends to be uniform; ECAP deformation of AZ31 magnesium alloy is experienced compression deformation before the first shear deformation occur, dynamic recrystallization first occurred in the grain boundary, subsequently extended to the grain, as the grain size decreases, dynamic recrystallization gradually reduced; The main mechanism of magnesium alloy refinement are dynamic recrystallization and intragranular refinement,when the grain refinement is to a certain extent, the grain will no longer be refined.Finite element analysize ECAP deformation of magnesium alloy using Deform software, the further understanding of the magnesium alloy ECAP do behavior. The results show that load - stroke curves are divided into three phases: the rapid growth stage, load slow growth phase, steady phase of load; Equivalent stress mainly was concentrated in and around the corner, the more close to the inside corner the greater the equivalent strain rate; Equivalent strain distribution is more complicated, strain distribution in central specimen is regular, the distribution of strain along the direction of the cross section is gradient distribution. The deformation is more complex in the head and tail of the sample and more regular specimen strain distribution in central. From the specimen in cross-sectional view of the central and the equivalent strain along the inside corner to the lateral direction, the strain distribution is uneven. Through analyzing numerical simulation results and the deformation of the samples after the morphology and microcosmic comparison, simulation was effective. |
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