Investigations on the preparation Characterization and property Evaluation of rheo cast al si mg alloy And al si mg sicp composites in the As cast and heat treated condition

Abstract

Aluminum-silicon alloy castings with a wide range of Si content have been extensively used in aerospace and automotive industry for the last two decades due to their high strength, low density, good castability, good corrosion resistance and weldability. However, the applications of both gravity die-casting and high pressure die-casting aluminum alloys in automotive and aerospace sectors have been restricted due to their poor quality resulting from harmful gas entrapment in the solidified metal as well as the presence of large amounts of micro-porosity. In recent years, rheological forming of semisolid metal such as Rheo-casting, Thixo-casting and Stir-casting of aluminum alloys have received more attention in producing aluminum alloy castings with enhanced mechanical properties compared with conventional die casting processes. With advent of RDC process, undesirable dendritic microstructure (tree-like grains) of die casting Al-Si-alloys can be replaced with non-dendritic (fibrous grains) microstructure, which gives rise to an unusual improvement in strength along with improved ductility of the Al-Si alloy castings. Many researchers have paid more attention on studying the effect of processing parameters on the microstructure of rheo-die cast Al-Si-Mg alloys. A large number research work was reported on the microstructure of Al-Si-Mg alloys in the semisolid condition as well as high solid fractions in semisolid of Al-Si-Mg alloys with 4 wt % to 7 wt % Si and 0.5 wt % and 1.0 wt %Mg respectively. Aluminium metal matrix composites have also emerged as advanced materials for several engineering applications, in particular automotive and aerospace sectors due to their excellent combination of properties like high strength, high stiffness, electrical and thermal conductivity, low coefficient of thermal expansion along with better wear and seizure resistance. Reports on mechanical properties and wear behaviour of RDC Al-Si alloys with SiCp reinforcement are very limited newline newline newline