Stir casting is an economical process for the fabrication of aluminum matrix composites. There are many parameters in this process, which affect the final microstructure and mechanical properties of the compos- ites. ...Stir casting is an economical process for the fabrication of aluminum matrix composites. There are many parameters in this process, which affect the final microstructure and mechanical properties of the compos- ites. In this study, micron-sized SiC particles were used as reinforcement to fabricate A1-3 wt% SiC composites at two casting temperatures （680 and 850 ℃） and stirring periods （2 and 6 min）. Factors of reaction at matrix/ceramic interface, porosity, ceramic incorporation, and agglomera- tion of the particles were evaluated by scanning electron microscope （SEM） and high-resolution transition electron microscope （HRTEM） studies. From microstructural char- acterizations, it is concluded that the shorter stirring period is required for ceramic incorporation to achieve metal/ce- ramic bonding at the interface. The higher stirring tem- perature （850 ℃） also leads to improved ceramic incorporation. In some cases, shrinkage porosity and intensive formation of A14C3 at the metal/ceramic interface are also observed. Finally, the mechanical properties of the composites were evaluated, and their relation with the corresponding microstructure and processing parameters of the composites was discussed.展开更多
In this study, large micron-sized Si C particles were fragmented via ball-milling process in the presence of iron and nickel powders, separately, to fabricate composite powders of Fe–Si C and Ni–Si C. Continuous fra...In this study, large micron-sized Si C particles were fragmented via ball-milling process in the presence of iron and nickel powders, separately, to fabricate composite powders of Fe–Si C and Ni–Si C. Continuous fracturing of brittle Si C powders leads to the formation of multi-modalsized Si C powders with size of from 50 nm to slightly higher than 10 lm after 36-h ball milling. The milled powders were then incorporated into the semisolid melt of A356 aluminum alloy to ease the incorporation of fine Si C particles by using iron and nickel as their carrier agents.The final as-cast composites were then extruded at 500 °C with a reduction ratio of 9:1. Lower-sized composite powders with slight agglomeration are obtained for the36-h milled Ni–Si C mixture compared to that of Fe–Si C powders, leading to incorporation of Si C particles into the melt with a lower size and suitable distribution for the Ni–Si C mixture. It is found that lower-sized composite particles could release the fine Si C particles into the melt more easily, while large agglomerated composite particles almost remain in its initial form, resulting in sites of stress concentration and low-strength aluminum matrix composites. Ultimate tensile strength(UTS) and yield strength(YS) values of 243 and 135 MPa, respectively, are obtained for the aluminum matrix composite in which nickel acts as the carrier of fine ceramic particles.展开更多
文摘Stir casting is an economical process for the fabrication of aluminum matrix composites. There are many parameters in this process, which affect the final microstructure and mechanical properties of the compos- ites. In this study, micron-sized SiC particles were used as reinforcement to fabricate A1-3 wt% SiC composites at two casting temperatures （680 and 850 ℃） and stirring periods （2 and 6 min）. Factors of reaction at matrix/ceramic interface, porosity, ceramic incorporation, and agglomera- tion of the particles were evaluated by scanning electron microscope （SEM） and high-resolution transition electron microscope （HRTEM） studies. From microstructural char- acterizations, it is concluded that the shorter stirring period is required for ceramic incorporation to achieve metal/ce- ramic bonding at the interface. The higher stirring tem- perature （850 ℃） also leads to improved ceramic incorporation. In some cases, shrinkage porosity and intensive formation of A14C3 at the metal/ceramic interface are also observed. Finally, the mechanical properties of the composites were evaluated, and their relation with the corresponding microstructure and processing parameters of the composites was discussed.
基金financially supported by the Iran National Science Foundation (No. 91002190)
文摘In this study, large micron-sized Si C particles were fragmented via ball-milling process in the presence of iron and nickel powders, separately, to fabricate composite powders of Fe–Si C and Ni–Si C. Continuous fracturing of brittle Si C powders leads to the formation of multi-modalsized Si C powders with size of from 50 nm to slightly higher than 10 lm after 36-h ball milling. The milled powders were then incorporated into the semisolid melt of A356 aluminum alloy to ease the incorporation of fine Si C particles by using iron and nickel as their carrier agents.The final as-cast composites were then extruded at 500 °C with a reduction ratio of 9:1. Lower-sized composite powders with slight agglomeration are obtained for the36-h milled Ni–Si C mixture compared to that of Fe–Si C powders, leading to incorporation of Si C particles into the melt with a lower size and suitable distribution for the Ni–Si C mixture. It is found that lower-sized composite particles could release the fine Si C particles into the melt more easily, while large agglomerated composite particles almost remain in its initial form, resulting in sites of stress concentration and low-strength aluminum matrix composites. Ultimate tensile strength(UTS) and yield strength(YS) values of 243 and 135 MPa, respectively, are obtained for the aluminum matrix composite in which nickel acts as the carrier of fine ceramic particles.
