HIGH CYCLE FATIGUE STRENGTH AND FATIGUE CRACK CHARACTERISICS IN SEMI-LIQUID DIE CASTING ALUMINUM ALLOY

摘要

Rotating bending fatigue tests were carried out on a semi-liquid die casting aluminum alloys. Comparing with the conventional casting alloy (AC4CH), the semi-liquid die casting alloy could reduce cast defects and porosities in the alloys, and could miniaturize structure sizes, therefore, the fatigue strength of the semi-liquid die casting alloy was well improved in comparison with the conventional AC4CH. According to the observation of the crack initiation behaviors, the cracks initiation sites were alternative of cast defects and eutectic silicon particles, and also, the crack initiation life varied with depending on the crack initiation sites. And, then crack propagation property was depended on the form and the distribution of eutectic silicon particles in the semi-liquid die casting alloys. As a results, the fatigue life was estimated from the crack initiation life and the crack propagation life, and the obtained fatigue life prediction gave a good agreement with the experimental life.