| As the lightest metal structural material, magnesium alloys have become the first choice of light weight weapon material. The vast majority of the magnesium alloys workpieces are die-cast products with low mechanical properties and a lot of casting defects, which resulted in bad performances of the products, so that it could only be used as low loading force parts. The mechanical properties of the magnesium alloy both at room temperature and elevated temperature as well as the anti-corrosion properties could be improved by adding rare erath elements. Moreover, extruding rare earth magnesium alloy could further enhance the overall mechanical performance of the new generation weapon by expanding its use as the main structure material to bear higher loading forces. Therefore, it is of great importance to carry out basic research relating to the extruding of rare erath magnesium alloy palte. The hot deformation behavior of the AZ80+0.4% Ce rare earth magnesium alloy and its microstructure evolution were studied, and the hot deformation maps of the alloy were also established.?1?Gleeble-3500 thermal simulation machine were used in order to study the hot deformation behavior of extruded AZ80+0.4%Ce magnesium alloy sheet. The flow stresses, peak stresses and peak stress strain of the deformed AZ80+0.4%Ce magnesium alloy increased with decreasing temperatures and increasing strain rates in the temperature range of 300-420? and strain rate range of 0.0005-0.5s-1 The mechanical properties of samples with different orientations exhibited anisotropic characteristics, which decreased with increasing strains and temperature and increased with increasing strain rates.?2? The phenomenological constitutive equations were established for 0°,45° and 90° samples respectively. The critical stresses and the critical strains with different samples were also obtained. The critical stresses and the critical strains of the AZ80+0.4%Ce magnesium alloy increased with the decreasing temperatures and increasing strain rates, and the critical strains were in the range of 30-50% of the peak strain. The critical strain in ascending order were 0°,90° and 45° samples, which were determined by different dynamic recrystallization mechanisms for the three samples.?3? Optical microscopy were used to analyze the microstructure evolution.The microstructure evolution for different samples showed strong anisotropic characteristics under low temperatures and high strain rates deformation, which could be attributed to different plastic deformation for respective samples. The microstructure evolution anisotropic characteristics tended to be the same with increasing temperatures and decreasing strain rates, which contributed to the decreasing mechanical properties anisotropic characteristics of different samples.?4? The dissimilarities of microstructure evolution for AZ80+0.4%Ce magnesium alloy with different sample deformed under low temperature and high strain rates were that the dynamic recrystallization grains area percentage decreased in the order of 90°,0° and 45°sample. However, the dissimilarities tended to disappear gradually with the increasing temperatures and decreasing strain rates.The cracks for different sample were prone to initiated at places where deformation band or the second phase located, thus leading to stress concentration, and the fracture mechanisms for these samples were microvoids coalescence. The plastic performance of 45° sample is the best, while that of 0° sample is the worst. Dynamic precipitations for AZ80+0.4%Ce magnesium alloy, which were more easily to be found in deformation bands, tended to be weakened with increasing temperatures, and the the sizes of dynamic precipitations phases tended to decrease with increasing strain rates. The ratio of the long axis and short axis increased with increasing strain rates and decreasing temperatures. The ratio for 45° sample was higher that of the 90° sample, and the ratio for 0° sample was the smallest.?5? Hot deformation maps for all the samples were established with three typical stability regions, namely region ?, ? and ?. Region ?, which has the lowest power dissipation is at 300-340?,5×10-4-5×10-3s-1; region ? is at 380-420?,5×10-2-5×10-1s-1; region ?, which has the highest power dissipation, is at 380-420?, 5×10-4-5×10-3s-1. The optimum hot deformation conditions for 0°,45° and 90° sample are at 380?,5×10-3s-1,380?,5 × 10-2s-1 and 380?,5 × 10-2s-1 respectively.This study laid a solid foundation both for the numerical simulation of AZ80+0.4%Ce magnesium alloy with basal texture and its optimized processing parameters. |
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