| Summary: | 碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 103 === Magnesium alloys have various characteristics, such as high strength, low density, strong shock absorption ability, electromagnetic shielding and good thermal conductivity. They are widely applied in electronic products and aerospace industries. In this study, in order to make the product have better mechanical properties, using dynamic recrystallization (DRX) to make grain refinement to increase the strength of the product by applying plastic deformation in hot-working. The flow stress of Magnesium alloy ZK60 can be obtained by compression test. The peak of the flow stress, including peak stress and peak strain, and the strain of 50% DRX strain can be applied in DRX prediction equation by using mathematical regression method. After the DRX prediction equation is done, key in FEM software DEFORM-2D to predict the effects of magnesium alloy ZK60 dynamic recrystallization behavior in hot-rolling and rolling process conditions. The simulation results show that a rolling temperature of 400 ℃ and a thickness reduction of 40% are the optimal conditions. An average grain size of 0.55 μm- 1.37 μm in the microstructure is obtained and the strength and formability of ZK60 magnesium alloys is improved.
Finally, this study has made one pass and multi-pass hot-rolling experiment by changing different process conditions, such as, temperature, pressure ratio and roll temperature, etc.. After the metallographic microstructure observation, comparison under the same process conditions degree of recrystallization and grain size, as well as do a series of mechanical properties are discussed and resolved to verify the correctness of the simulation. The experimental results show the average grain size of sheet temperature of 400 ℃ after rolling have large errors, because the grain growing rate is too fast. The error of the measurement result of average grain size at 300 ℃ is about 30%.
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