THE MICROSTRUCTURE AND MECHANISM OF FATIGUE CRACK INITIATION OF 2024-T3 AND 2524-T34 ALUMINUM ALLOYS

摘要

The micro structure and mechanism of fatigue crack initiation of 2024-T3 and 2524-T34 Al alloys were investigated at the present paper.Four-point bending and tension-tension fatigue tests were conducted on the test alloys along the rolling direction at room temperature and frequency of 15Hz,R=0.1.It was found that the flat grain was elongated along the rolling direction,showing the laminar grain structure. The majority of fatigue cracks of 2524 were initiated at coarse particles,a few of them was formed on sites of material defects or slip bands. The intrusion and extrusion induced by slip band in the Al cladding layer provided principal fatigue crack initiation sites for 2024 Al-cladding aluminum alloys.