Study on the Effects of Squeeze Pressure on Mechanical Properties and Wear Characteristics of near-Eutectic Al–Si–Cu–Mg–Ni Piston Alloy with Variable Cu Content

Abstract

This paper discusses the effects of the squeeze pressure on the microstructure, wear characteristics and mechanical properties of near-eutectic Al–Si piston alloys with variable copper (Cu) content. The paper starts with a description of Al–Si alloys and the features that make them desirable for use as piston alloys. The impact of the alloying elements on the mechanical properties, microstructure and wear characteristics is also discussed, where it is determined that adding alloying elements such as Cu, Mg and Ni results in improved strength and good casting properties. The paper also discusses the microstructural and material strength improvements that are achieved using the hybrid squeeze casting process and various heat treatment solutions. To evaluate the validity of these methods, the strength of the Cu-enriched Al–Si alloy as-cast and after heat treatment is analysed, and the results are compared. The results are for both gravity die casting and squeeze casting. Various techniques are used to analyse the chemical, mechanical and wear properties of the Al–Si alloys, including chemical analysis using optical spectrometry, heat treatment testing, microstructural observation, tensile testing and wear testing using scanning electron microscopy. The increase in Cu content in Al–Si alloys from 0 to 3% wt causes an increase in the ultimate tensile strength and hardness. Heat treatment and pressure application to the cast sample also result in improved mechanical properties, a fine and modified microstructure, improved wear resistance and a lack of surface porosity compared to the gravity die-cast samples. These characteristics are suitable for reducing the mechanical losses of Al–Si pistons as well as the fuel consumption.