| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 101 === The mechanical behavior of magnesium metal matrix composites (Mg MMCs) are superior to those of the pure metal alloy. By adding the reinforcement, such as particles, short fibers, or continuous fibers, into the metal matrix can improve the composite’s mechanical properties. Three different particle size of SiCp are dissolved into AZ61 by the stir-casting method, and then the Mg-based composite is fabricated. Before extrusion, solid solution treatment was conducted to improve the ductility of the material. Eventually, the mechanical properties of the composite before and after the extrusion with aging treatment are discussed.
The results shows that the ultimate tensile strength, yielding strength, ductility and hardness of magnesium matrix composites will decrease with increasing the size of reinforcement. The ultimate tensile strength, yielding strength, ductility and hardness of AZ61/5 wt% SiCp/10 μm ingot are 146.7 MPa, 66.6 MPa, 3.8% and 59.4 HV, respectively. Compared with the AZ61/5 wt% SiCp/1 μm ingot were reduced 19.2%、10.7%、36.7%、2.5%. For the extrusion rod, AZ61/5 wt% SiCp/1 μm exhibits better mechanical properties, which will decrease with increasing the reinforcement size. The ultimate strength, yielding strength, ductility and hardness are 316.0 MPa, 147.5 MPa, 16.6% and 69.1 HV, respectively. In addition, aging treatment will enhance the ultimate strength, yielding strength and hardness of rods.
In this study, microstructure of AZ61/5 wt% SiCp/10 μm ingot shows Mg2Si compound at the grain boundaries after solid solution treatment. The Mg2Si compound will affect the mechanical properties of magnesium matrix composite. From the experiment results, the mechanical properties decreased greatly with the reinforcement size of 10 μm.
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