Analysis of the Failure of the Engine Piston of the AlSi Alloy

Abstract

The aim of the article is piston damage evaluation of a highly exposed combustion engine. The analysed piston was made of an AlSi-based alloy. Atypical damage, which occurred relatively early in the lifetime of the component, was evaluated by metallographic and fractographic analyses. The analysis took into account influences of mechanical and thermal fatigue processes in relation to the microstructure of the material. The metallographic observations of the microstructure revealed the occurrence of cracks extending over the secondary phases and precipitates. Cracks were initiated on the coarser Si phase particles. The crack initiation site is located at the root of the bridge between the sealing piston rings. The damage of the piston was metallographically documented in wide range.