1995 Volume 45 Issue 11 Pages 671-676
Automobile engine materials require higher thermal fatigue resistance with increasing combustion temperature. Porosity in aluminum alloy castings is a serious defect which decreases the strength of the castings. In this study, the effect of porosity on thermal fatigue lives was investigated using JIS AC2B-T6 alloy castings. The thermal fatigue lives were evaluated by a newly-developed test method using restraining holders composed of low-thermal-expansion material. In a high total strain range, the maximum pore area on a fracture surface correlated to the thermal fatigue life. In a low total strain range, on the other hand, the total porosity area on a fracture surface correlated to the thermal fatigue life. It has been clarified that the fracture mechanism was changed by the total strain range, affecting the correlation between the porosity and the thermal fatigue lives.
