The surface liquid segregation(SLS) phenomenon in semi-solid metal-high pressure die casting(SSM-HPDC) plates of 7075,2024,6082 and A201 was investigated by different techniques.Depth profiles were determined by firstly measuring the chemical composition of the surface of the plates using a Thermo Quantris optical emission spectrometer(OES).Material was then removed by a grinding process followed by measurement of the amount of material removed and chemical analysis.Chemical profiles of the main alloying elements were plotted for the cross-section of the plates in the as-cast and T6(after solution treatment) temper conditions.Vickers hardness profiles from the surface to the centre of the plates were determined.Metallographic samples of cross-sections of the castings were prepared and evaluated using a scanning electron microscope.The results show that surface liquid segregation in SSM-HPDC alloys causes significant differences in properties between the surface and the bulk of these castings in both the F and T6 temper conditions.
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