An investigation of structure-property relationship in the Al-Si alloys produced by semi-solid casting process

This thesis comprises of a study of the semi-solid casting of A357 alüminium-silicon alloy. The cooling slope casting process was employed to produce non-dendritic feedstock. The molten alloy with 620 oC, 630 oC and 640 oC superheat was poured on the surface of the inclined plate in 60o angles and various lengths (250, 350 and 450 mm). It was found that 630 oC casting temperature with 350 mm cooling length produced an optimim non-dendritic structure having 45 ?m cell size and 0.60 shape factor. The feedstock having optimum non-dendritic parameters were then held at temperatures of 572 oC with various (1,3,5 and 7 min.) izothermal holding times before water quenching. 5 min. isothermal holding time at 572 oC temperature resulted in 68?m cell size and 0.70 shape factor. Those feedstocks in semi-solid state (47% liquid fraction) were injected with using 1, 1.5, 2, and 2.37 m/s injection speed into mold which has 150 ºC constant temperatures. The results indicated that 2.37 m/s injection speed produced 74?m cell size and 0.60 shape factor. The values of tensile strength, 0.2% yield strength and % total elongation were increased when 2.37m/s enjection speed applied.