Abstract:
Cooling slope can be an effective technique for grain refinement and a step towards thixotropic semi solid metallurgy. This study investigates the processing of Al-Si-Mg alloy in semi solid phase using sloping plate technique. A newly determined contact time parameter was used obtaining a correlation with inclination angle and flow velocity. The pouring temperature effect (640˚C, 660˚C and 680˚C), contact time (0.04S,0.09S,0.13S) and inclination angle 20˚,40˚ and 60˚ and sloping plate length was studied on microstructure and mechanical properties on commercially available Al-Si-Mg alloy (LM 25). We prepared nine tensile testing specimens in conformance to ASTM E8M using sloping plate casting. The microstructure analysis and mechanical properties of the alloy were compared with an as cast and as received non modified, non-refined Al-Si-Mg alloy (NGM) and commercially produced magneto hydro dynamically stirred Al-Si-Mg (A 356) alloy (MHD A 356).
The microscopic study and improved mechanical properties e.g % elongation and hardness of specimen confirmed the grain refinement through slopping plate casting. Further, the mechanical properties like yield strength, ultimate tensile strength and ductility was determined, after collecting data by using computer controlled Universal Testing Machine MTS 810 as per ASTM standard E8M. Brinell hardness tests were performed according to ASME standard E0010-01E01 on universal Hardness Tester of the specimen were examined in view of the input parameters and concluded optimum results.
The role of cooling slope was found as the extraction of heat thereby affecting the grain size and morphology both on slope interface and bulk melt by creating thermal under cooling necessary for columnar to equaixed transition(CET) and also influencing dominant nucleation mechanism.
