This paper reports a study of the Coefficient of Thermal Expansion (CTE) of Al7075/basalt short fiber Metal Matrix Composites (MMCs) as a function of temperature and reinforcement.
The percentage of reinforcement was varied from 2.5 to 10 wt. % in steps of 2.5% and the composites were prepared by the liquid metallurgy technique. Using Thermal Mechanical Analyzer (TMA) model DuPont 943 equipment, the changes in the linear dimension as a function of temperature is recorded as Percent Linear Change (PLC). The temperature of the tests ranged from 50°C to 300°C in the steps of 5°C both in the heating and cooling cycles. The results show that the CTE significantly increased with increasing temperature but decreased with increasing basalt fiber. These phenomena are explained.
The coefficient of thermal expansion of Al7075/basalt short fiber composites have been systematically studied using thermal mechanical analyzer technique. The CTE of both unreinforced matrix alloy and the composite is found to increase with increasing temperature but decreased with increasing basalt fiber reinforcement, which is due to high reinforcement stiffness, matrix alloy grain modification, and the dislocation density of the composites due to the difference in CTE between matrix and reinforcement.
The dimension change of composite has varied almost linearly with the increase in temperature with a rapid increase in the range (280-300°C). This is due to increase distance of lattice. The residual thermal strain is found to increase with the increase in the weight percentage of basalt short fiber content. The evaluation of thermal stresses indicates the existence of considerable magnitude of thermal stresses within the short basalt fiber reinforced composite. A marginal increase in the CTE value is observed for the basalt short fiber reinforced composite samples when compared to as cast material. Further, the CTE values remain almost uniform over a greater temperature range for the basalt short fiber reinforced composite materials, which is considered as an advantage.
S. Ezhil Vannan, Professor, Deparment of Mechanical Engineering, HKBK College of Engineering, Karnataka, India;
Paul Vizhian S., Professor, Deparment of Mechanical Engineering, University Visvesvaraya College of Engineering, K.R Circle, Bangalore University, Karnataka, India;
R. Karthigeyanc, Research Scholar, Deparment of Mechanical Engineering, Adhiyamaan College of Engineering, Tamil Nadu, India.