抄録
Mechanism of fatigue fracture has been widely studied by many investigators. It has not been clarified, however, whether surface features or sub-structures are essential to fatigue crack initiation. In this investigation, as the first step to challenge this problem, the crystal orientation dependence of fatigue damage is studied on 99.99 % pure aluminium single crystals by X-ray micro-beam technique.
The results obtained are as follows:
(1) Fatigue damage is accelerated in the crystal orientation which has equally large Schmid factor both on Primary and Critical slip planes, but it is restrained as Schmid factor on Conjugate slip plane increases.
(2) The formation of extrusion and intrusion is restrained near [100] direction which has large Schmid factor of cross slip system. It is suggested that the persistent slip bands are coplanar.
(3) The configuration of fatigue damage depends on the crystal orientation.
(4) Secondary slip system plays an important part in the formation of fatigue damage. It is remarkable in the Stage II of crack propagation.
