Abstract
The effect of test temperature on fatigue damage was studied on pure aluminium in fully reversed plane bending by using the X-ray microbeam technique. As a result, the fatigue strength was found to decrease with increasing test temperature. As the test temperature was elevated, the total misorientation β, the excess dislocation density (Db)max and (Db)min increased, and larger and more polygonized subgrains were formed. This resulted in the reduction of fatigue strength.
The propagation rate of fatigue crack dl/dN was dependent on test temperature and not uniquely expressed by a power function of the stress intensity factor. However, the excess dislocation density (Db)max and the subgrain size t in the grain at crack tip were closely related to the crack propagation rate dl/dN by the following equations independently of test temperatures: dl/dN=3.26×10-24 (Db)max1.79 and dl/dN=3.08×10-3t-3.69
