الفهرس 
الغلافOnly 14 pages are availabe for public view
 |  | from | 212 |  |  |
| | | from | 212 | | |
Abstract
Casting process using the cooling slope plate (CSP) has gained significant importance for the manufacturing of semisolid feedstock of aluminum alloys which find applications in the automotive and aerospace industries. The effect of the pouring temperatures and mould type on the microstructure of A356 aluminum alloy via semisolid casting using CSP has been investigated. The semisolid casting using CSP was studied at different designated pouring temperatures (625, 640, 680, 700 °C) above the liquidus temperature of the investigated alloy of 624 °C. The prepared alloy that became semisolid at the end of CSP was consequently poured into two different types of moulds: sand and metallic moulds. In case of using the sand mould, the results showed clearly that without using CSP, the α-Al phases became a coarse dendritic structure with the average length of about 287.5 μm. With using CSP, the α-Al phases developed the fine globular structure with the average grain size of about 72.6 μm at the optimum pouring temperature of 640 °C. In case of using the metallic mould, the α-Al phases became dendritic structure with the average length of about 115 μm without using SCP. While, The α-Al phases developed the fine globular structure with the average grain size of about 47.5 μm at the optimum pouring temperature of 680 °C with CSP. The improvement of the tensile properties for the A356 aluminum alloy produced by semisolid casting using CSP is related to the modification and refinement of α-Al phases. The ultimate tensile strength and elongation of the prepared alloy using sand mould significantly increase from 102 MPa and 1.175% without semisolid casting to 113 MPa and 3.6 % with semisolid casting at the optimum pouring temperature of 640 °C, respectively and then gradually decrease with a further increase in pouring temperature. In case of using metallic mould, the ultimate tensile strength and elongation of the prepared alloy significantly increase from 140 MPa and 2.55 % without semisolid casting to 155 MPa and 9.2 % with semisolid casting, respectively and then gradually decrease with a further increase in pouring temperature. The fracture mechanisms have been also investigated. The improvement of the hardness for the investigated A356 aluminum alloy produced by semisolid casting using CSP is related to the modification and refinement of α-Al phases. In case of using the sand mould, the hardness of the investigated A356 aluminum alloy significantly increases from 60 HB without semisolid to 64 HB with semisolid at the optimum pouring temperature of 640 °C and then gradually decreases with a further increase in pouring temperature. In case of using metallic mould, the hardness significantly increases from 61 HB without semisolid to 64 HB with semisolid at the optimum pouring temperature of 680 °C and then gradually decreases with a further increase in pouring temperature.