ISSUE 4/2008

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Ramamurthy Mahadevan and Ramaswami Gopal, Chennai, India
Selectively reinforced squeeze cast pistons

This paper presents the development of a selectively reinforced metal matrix composite piston through squeeze casting and its functional comparison with a conventional gravity diecast Alfin piston in automotive application.
Special characteristics, such as reduced weight, lower thermal expansion, improved wear resistance and higher strength, have been the focus of attention in the development of MMC pistons. Among the various processing methods squeeze casting provides several advantages as it combines the beneficial aspects of casting as well as forging. Selectively reinforced pistons were produced using a specially designed squeeze casting machine jointly developed by IIT Madras and India Pistons Ltd. through a collaborative project between industry and institute. The material system consists of a eutectic Al-Si alloy and aluminium-silicate short fibre preforms. The pistons, which have been reinforced in the top ring groove and land area, were fitted in S3-24 Simpson diesel engines for performance comparison with conventional Alfin pistons. The engine has already completed 1000 hrs endurance testing apart from scuffing and thermal cycling tests, and the results are very encouraging. The ring wear, groove wear, oil consumption and blowby were some of the characteristics checked for comparison. These results clearly indicate that there is a potential for replacing the current Ni-resist aluminium alloy pistons with selectively reinforced squeeze cast aluminium pistons (MMC).

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