Effect of end chills, reinforcement content and carburization on the hardness of LM25-borosilicate glass particulate composite

Abstract

Aluminium metal matrix composites (AMCs) are widely employed in aerospace and automobile applications. Thus, they are required to operate reliably under a severe corrosive, high temperature and carbonaceous environments, without undergoing any deterioration in their mechanical properties. The paper is the compilation of the experimental results and analysis carried out to investigate the effect of different end chills, reinforcement content and carburization on the LM25 aluminium alloy reinforced with borosilicate glass powder. The composites are prepared via stir casting route by varying the weight percent (wt.%) of the reinforcement starting from 3 wt.% and going up till 12 wt.% with an increment of 3wt.% in every step. To obtain quality castings, end chills are placed within the sand mould. The specimens drawn from the chill-end of the castings are pack carburized in a muffle furnace for a set duration of time. The hardness of the specimens before and after carburization is recorded. The analysis of the results illustrates that the hardness increases linearly with the increase in the reinforcement content within the matrix from 3 wt.% up to 9 wt.%. It is also evident that the Volumetric Heat Capacities (VHC) of the chill material bears a strong effect not only on the quality of the castings produced but also on the hardness of the AMCs. Carburization leads to carbon deposition on the surface causing a change in the hardness of the specimens.

Keywords

• volumetric heat capacity
• aluminium metal matrix composites
• particulate reinforcement
• hardness
• directional solidification
• stir casting