Influence of non-geometric effect of PSB on crack initiation in aluminium single crystal

We present an investigation of the crack initiation by cyclic deformation on the two special surfaces of pure aluminium single crystal. One is the side-surface containing the active Burgers vector, the other is the top-surface forming the smallest angle with the active Burgers vector. The fatigue test is performed at the constant resolved shear stress amplitude (5 MPa), zero mean stress. Experimental results show that many microcracks are initiated on the side-surface on which no PSB surface topographies are formed during cyclic deformation. Cracks on the side-surface are short with mean length of about 10 μm and distributed approximately in a similar direction, perpendicular to the active Burgers vector, whereas on the top-surface cracks, similar to those reported before, are not as obvious as those on the side-surface. Observations by scanning acoustic microscopy show that the fatigue damage on the side-surface is much deeper than that on the top-surface. A model of crack nucleation by voiding is suggested.