Study On Microstructure And Mechanical Properties Of Spray Deposited High Silicon Aluminum Alloy

Hypereutectic Al-Si alloys are widely used in the automobiles and electronic industries due to their lower density, lower thermal expansion coefficient, excellent wear resistance characteristics and mechanical properties. Especially, the content and morphology of silicon has an important effect on performance of these alloys. In this paper, hypereutectic Al-Si alloys have been manufactured by spray forming technique which effectively refines the grain size of matrix and secondary phases to improve the alloy properties.Compared with conventional ingot casting, the primary silicon grows into granule with 4-8μm and uniform distributes in Al matrix by spray forming technique, which significantly improves alloy microstructure.The compression testing resultes show that the stress decreased with the decrease of strain rate or the increase of test temperature. At the same time, compressed sample surface crack reduces, but increases while deformation temperature is too high. Compared with compressed sample surface, the optimum process parameter can be gotten with the temperature at 450℃and strain rate between 0.005s-1-0.01s-1. The flow stress of the high-silicon aluminum alloy during hot-compression deformation can be described by the hyperbolic sine function.The billet was hot extruded into a bar with the diameter of 20mm, and its density was increased with porosity eliminated. The microstruction of alloy was refined and the needle phase was extruded into small particles.We studied solution and aging treatment to the bar and got the final optimization of the alloy heat treatment process: solution treatment at 470℃for 1.5h and natural aging for 48h, then artifical aging treatment at 120℃for 24h. The alloy was subjected to tensile testing after solution and aging treatment, and the results indicate that tensile strength and elongation rate of Al-Si alloy reaches 440.5 MPa and elongation for 1.22%. The tensile strength decreases and the elongation rate increase with the increased of temperature, 267.4 MPa and 6.42% at 300℃. Spray forming high-silicon aluminum alloy wear-resisting property is better than cast iron material. With the wearing time increasing, the wearing capacity of high-silicon aluminium alloy steadly grows, but cast iron grows rapidly.