The Evolution of Aluminium Based Piston Alloys for Direct Injection Diesel Engines

The trend in recent years towards increased engine ratings across the whole range of piston applications has led to an increase in the durability requirements for piston alloys. New piston alloy development has been particularly important in the light vehicle diesel (LVD) field, where the race for improved engine performance has led to significant increases in the temperatures and pressures experienced by the piston during engine operation.

The demand by oem's for cost effective material solutions for these high per-formance, high volume applications has required piston manufacturers to develop improved aluminium based casting alloys in a short timeframe. Federal-Mogul has been at the forefront of both material and process development in the area of cast aluminium alloys for high duty applications.

This paper describes the material property requirements for direct injection diesel engine pistons and how increases in these requirements, particularly in the area of high temperature fatigue resistance, has lead to the evolution of a family of new piston alloys over the past few years. The paper also describes the fundamental metallurgical work on the relationships between production process conditions, alloy microstructure and material fatigue resistance carried out by Federal-Mogul. The paper concludes with the use of this fundamental knowledge in the rapid development of an improved performance piston alloy for LVD applications, now in volume production, and finally future development trends in new piston materials are discussed.