Abstract

Fracture surfaces of amorphous selenium broken in flexure at room temperature have been studied. The fracture velocity was found to vary in different regions of the fracture surface. Peculiar features were observed in a transition zone between fast and slower fracture. In this zone cleavage steps with a nearly constant spacing of approximately 1 μ were found. Occasionally long cleavage whiskers—up to some millimeters long—were observed. Within certain regions the cleavage steps were crossed and interrupted by two line systems. The maximum fracture velocity has been measured to 350 m/sec. Further the velocities of ultrasonic longitudinal and shear waves were measured to 1820 m/sec and 930 m/sec, respectively. Based on these results the two line systems in the transition zone can be interpreted as ``Wallner lines'' with sources within the zone.