Evolution of Al-Si-Cu alloy in piston of diesel engine during knock damage.

• The failure process mainly includes the erosion damage of the original passive film and the subsequent peeling of the surface material. • Carbon deposit on the crown of piston react with the surface of the aluminum matrix to form brittle phase (Al 4 C 3 and Al 2 O 3). • The residual piston hardness in the cross section of the damage zone decreases significantly as the ablation level increases. The failure mechanisms of Al-Si-Cu alloy in piston of diesel engine due to abnormal combustion are not fully understood at present. In this paper, the bench test of the original piston was carried out, which induced knock combustion by monitoring of the pressure signal in the cylinder. The results show that the failure process mainly includes the erosion damage of the original passive film and the subsequent peeling of the surface material which was proved by XRD, optical and scanning electron microscopy, 3D confocal laser scanning microscope and other research methods. During erosion damage, carbon deposit on the crown of piston react with the surface of the aluminum matrix to form brittle phase (Al 4 C 3 and Al 2 O 3). In addition, the residual hardness in the cross section of the damage zone decreases significantly as the ablation level increases. [ABSTRACT FROM AUTHOR]