Thermal expansion and fatigue properties of automotive brake rotor made of AlSi–SiC composites

Abstract

Automotive brake rotors were made of Al-9Si and Al-12Si reinforced with 10 and 20% SiC particles using stir casting method. Microstructures of brake rotors made of composite revealed uniform distribution of SiC particles, primary phase (⍺-Al) and modified eutectic Si. Grain refining was also observed due to the addition of SiC particles. Coefficient of thermal expansion (CTE) and thermal strain response curves during heating and cooling cycles between room temperature and 350ﾟC for produced brake rotors made of Al-9Si and Al-12Si and their composites. Al-12Si and its composites have lower CTE and near zero residual strain. Thermal fatigue studies were carried out on the brake rotors made of composite and break rotor made of cast iron for comparison. After 80 cycles, hardness, microstructure and XRD analysis were conducted. The results showed that the strain and temperature followed the same path on cooling as on heating, indicating that both hystresis loop and residual strain were absent. At the same time, the crystallinity of the brake rotors made of composite was improved by exposure to thermal cycles, while it was worsened in case of break rotor made of cast iron on the long run.