Abstract—The mechanical properties of composite materials are strongly dependent on micro structural parameters of the system. The evolution of microstructure depends largely on the cooling rate during phase change. Though the microstructure evolution depends on many process parameters, the final structure is decided by the cooling conditions during solidification. The mold material has a decided effect on the structure formation. The use of end chills during casting not only favors directional solidification but also accelerates solidification. Faster cooling rates give rise to finer structures and improved mechanical properties. In this work an attempt is made to vary the cooling rate of AL-B4C, composite cast using stainless steel, cast iron and copper chills. The microstructure and micro hardness of the chill cast specimens are analyzed and reported. It is observed that the chill material has a significant influence on the microstructure and hardness of the cast specimens. Finer structure and better hardness were observed with the specimens cast using copper chills, whereas, cast iron and stainless steel chills gave rise to coarse structure with reduced hardness.

Index Terms—End chill, Cooling rate, Directional solidification, Microstructure

Cite: Leela B N and K V Sreenivas Rao, "Microstructure and Microhardness of Chill Cast Al-B4C Composites ," International Journal of Mechanical Engineering and Robotics Research, Vol.1, No.3, pp. 450-456, October 2012.