Correlation between melt quality and fatigue properties of 2024, 6063 and 7075

Abstract

Extruded 2024, 6065 and 7075 alloys were subjected to Strain Induced Melt Activated (SIMA) process and average of 80 µm spherical grains were obtained. T6 solution heat treatment was carried out to all alloys. In addition to the typical water quenching at 20°C, temperature controlled bath was used where the water was set to 80°C and some samples were quenched in that water. High mean stress values were selected (0.9, 0.8 and 0.7UTS) and load stress ratio (R) was selected to be 0.1. The fatigue test results were analyzed by Weibull and the distributions were compared with metal quality. SEM analysis was carried out on the fracture surface. A good correlation was found between bifilm index and the fatigue properties; as the quality was lowered, the scatter of the test results was increased.