| The benefit of rapid solidification is well understood in synthesizing aluminum alloys for high-temperature applications. More over the stringent requirements of the automotive and aerospace industries have prompted the design of advanced. Materials with high strength to weight ratio, low coefficient of thermal expansion and high wear and corrosion resistance. The hypereutectic Al-Si alloys containing transition metals are unique materials due to their particular properties at elevated temperatures. Conventional techniques of processing of alloys lead to a coarse-grain microstructure and give rise to inferior mechanical properties. This has led to the processing of these alloys through rapid solidification techniques Such as spray forming, provide a substantial chemical and microstructures homogeneity together with refinement in grain size and second phase particle size.In this paper , an inert gas atomization technique was employed to produce spray deposits of an Al-Si alloy. The spray-deposited alloy was subsequently hot extruded with a reduction ratio of 8:1 and extrusion temperature of 480℃. The microstructural features of the as-spray-deposited and extruded alloy were examined using optical, scanning election microscopy techniques.Results showed that a fine particulate, morphology of primary Si phase uniformly dispersed in the matrix ofα-phase was observed in spray-deposit of Al-Si alloy. Microstructures refinement was further increased in the hot extruded alloys. The room temperature tensile tests of spray formed and extruded alloys showed considerable increase in their strength over that of the as cast alloys. It has ultimate tensile strength of 511MPa in as deposited and extruded condition. In addition, the tensile at 100℃to 300℃were determined after T6 heat treatment. The improvement in mechanical properties of spray formed alloys is discussed in light of the microstructure modifications induced during spray deposition process. |
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