An Influence of Cooling Rate on the Fatigue Reliability of Metal-Molded Aluminum Alloy Castings

Abstract

An influence of cooling rate on the fatigue reliability of aluminum alloy castings (AC4CH) was investigated. The results obtained were as follows: (1) As the cooling rate of AC4CH was increased, the porosities and the microstructure were controlled fine. (2) The fatigue strength of AC4CH produced through rapid cooling rate was superior to that produced through slow cooling rate, specially on the fatigue limit (N = 107). (3) The effect of stress gradient on the fatigue limit is due to the probability that the maximum stress can put on the largest porosity in the specimen. (4) Micro porous defects were always observed at the origin of fatigue crack. Then, it could be interpreted that the fatigue life was related to the size of porous defect, based on fracture mechanics. (5) From the above relation and the statistical analysis on the size of porous defect, the fatigue limit of 99% remaining probability could be estimated. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.