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Characterization of Al-7Si-Mg-Cu turbine impeller produced by investment casting
Syahid M.
Advanced Materials Research
Abstract
Application of a light-weight material, such as an aluminum alloy, on a turbine impeller can enhance the efficiency of an Organic Rankine Cycle power plant that operates at temperatures below 150 °C. The density of an aluminum alloy only one-third that of steel. However, increased strength of aluminum alloys is needed for turbine impeller qualification. Investment casting was chosen to produce radial inflow turbine impeller due to their complex geometry and precision. It can replace machining process, which is time-consuming and less efficient because of material removal. This study describes the investment casting process used to produce a radial inflow impeller turbine. The study also identifies defects, microstructures and properties of radial inflow turbine impeller. The turbine impeller were produced from Al-7Si-4Mg alloy with 0.38, 3.82, and 6.0 wt. % Cu. Visual examination showed that the turbine impeller was free of macro defects and misruns. Microstructures were characterized by Optical Microscopy and SEM. The structures consisted of α-Al, Si eutectic, AlMgSi, AlMgFeSi (Chinese script) and CuAl 2 . The higher hardness value of 54HRB was affected by Cu content due to the good mechanical properties of fasa CuAl 2 .