Effect of Chills on the Mechanical Properties, Wear Properties and Microstructure of Al 6061 Alloy Subjected to B4C Reinforcement Additions

Abstract

In the present investigation, successful attempts were made to produce aluminium alloy conforming Al 6061 specification in green sand moulds with and without the boron carbide (B4C) reinforcement additions and using chills. Chills promote directional solidification and hence results in improvement in mechanical properties. Three different chills materials namely copper, cast iron and mild steel having dimensions 130  40  6 mm has been used. These chills were placed at the bottom and side of the mould cavity, and the molten metal was transferred into the prepared moulds. After solidification and cooling of the metal, the castings were separated from the moulds, specimen for the assessment for the mechanical properties and wear properties (in dry sliding condition) were machined from the above castings. It is seen from the results of the investigation that improvement in mechanical properties and wear resistance properties to an extent of 40% has been noticed, indicating that chill material has an influence in enhancing the mechanical properties and wear resistance properties. Microstructure study confirms the presence and uniform distribution of boron carbide reinforcement. Castings made using copper chills exhibit higher mechanical and wear resistance properties compared with other two chill materials. The results of the present investigation are quite encouraging and the same is presented in following sections.