| SiCp can effectively refine the microstructure of aluminum alloy and improve its mechanical properties. However, poor wettability between SiCp and Al matrix limits the further development of SiCp/ZL105 composite's research and application. Therefore an electromagnetic stirring(EMS) technique combined with a high-temperature oxidation method were used to prepare a SiCp/ZL105 composite. The incorporation of SiCp was during the semi-solid range of ZL105 alloy. The influences of SiCp additive amount, EMS parameters(applied voltage and stirring frequency) on the microstructure, tensile properties of composites were researched in detail. The results showed that, appropriate addition of SiCp can refine the primary ?-Al and the eutectic Si, and improve their distribution. The secondary dendrite arm spacing of ?-Al, and the mean area and aspect ratio of eutectic Si were decreased significantly. At the same time, the Fe-rich phase(? phase) was changed from intensive bone shape into a dispersion type. On the other hand, adjusting EMS parameters can change the disorder severity of melt flow, influencing the distribution of SiCp in Al matrix. So it can play a indirect role on microstructure. When the SiCp's additive amount, the applied voltage and the stirring frequency were 1.5wt.%, 350 V and 35 Hz, the ultimate tensile strength and elongation of composite were reached up to 238.62 MPa and 5.23%. When it compared to the matrix, they were increased by 24.57% and 37.27% respectively.T6 heat treatment was used to process the ZL105 matrix and its composite that contained 1.5wt.%SiCp. The microstructure evolution during heat treatment, involved mechanisms and mechanical properties were discussed. Spheroidization of eutectic Si, dissolution of Al2 Cu that induced skeletal outline clear occurred during solution treatment. The optimal holding time for composite(6h) was shorter than that for matrix(9h). After aging, some precipitates of Al2 Cu were observed through TEM inspection. After T6, the hardness of matrix and its composite were 91.81 HV and 101.86 HV, which were increased by 14.52% and 17% respectively when it compared to the as-cast ones. In terms of tensile properties, the ultimate tensile strength and elongation of matrix after T6 were 246.54 MPa and 5.94%, which were increased by 28.7% and 55.91%. On its fracture, the cleavage planes were decreased significantly, and there were extensive dimples emerged. The ultimate tensile strength and elongation of composite after T6 were 273.64 MPa and 6.12%, which were increased by 14.68% and 17.02%. There was few cleavage planes on its fracture, instead of many dispersive and small-sized dimples.Dry sliding wear tests at ambient temperature were processed to as-cast ZL105 alloy, SiCp/ZL105 composites before and after T6. The effect of heat treatment on friction and wear properties of composite was researched. The results showed that, wear volume and coefficient of friction(COF) increased with normal load. And wear volume and COF for SiCp/ZL105 composite after T6 were all reached to the lowest under an invariable load. From the view of mechanisms, at low loads(15, 30N), abrasive wear and oxidative wear were primary. When the applied load was 60 N, there existed plastic deformation of certain extent. At high load(90N), as-cast ZL105 alloy exhibited severe plastic deformation. And plastic deformation and delamination were the main mechanism. With the addition of SiCp, the serious extent of delamination was weakened. After heat treatment, wear surface became smooth and flat, and there was no obvious signs of cracking, which indicated the composite after T6 had excellent friction and wear properties, and good wear resistance. |
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