| Summary: | 碩士 === 國立中正大學 === 機械工程學系暨研究所 === 99 === The mechanical characteristics of magnesium metal matrix composites (Mg MMCs) are superior to those of the pure metal alloy; Adding the reinforcement, such as particles, shot fibers, and continuous fibers, to the metal matrix can improve the composite’s mechanical properties. SiCP is dissolved into AZ61 by the stir-casting method, and then the Mg-based composite is fabricated. The Mg-based composites are extruded under the conditions of 300oC and 400oC and the material plastic flow inside the die is analyzed with the finite element simulations. After extrusion, solid solution treatment of the products are conducted to improve their mechanical properties. Eventually, the mechanical properties of the composite before and after the extrusion with aging treatment are discussed.
From the experimental results, it is known that the yielding strength and hardness of AZ61-Billet are 58MPa and 55.94HV, respectively. The yielding strength and hardness were improved by 7.4% and 5.4%, respectively, for 5wt%SiCp Billet. The yielding strength and hardness of AZ61-tube are 129MPa and 63.9HV, respectively, under extrusion temperature of 400oC, and its yielding strength and hardness are improved by 9.3% and 3.1%, respectively, after adding 5wt%SiCp; whereas, 10.9% and 8.9% increases are obtained under extrusion temperature of 300oC. After T5 aging treatment, the yielding strength and hardness of AZ61-tube are further increased by 10.1% and 8.3% under extrusion temperature of 400oC; and 12.4% and 18.4% with 300oC. With extrusion temperature of 400oC and T5 aging treatment, the ultimate strength obtained is 315MPa, the yielding strength is 145MPa, the ductility is 15.6%, and the hardness is 75.63HV.
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