On Fatigue Deformation and Fatigue Crack Initiation in Pure α-Titanium

Abstract

A study by electron-microscopy has been made of the behaviour of deformation and crack initiation in fatigued pure α-titanium. Plastic deformation is intensified at twin interfaces and the twin interfaces become searated: the serrations are accommodated by closely spaced kink boundaries. The pre-existing twins are broken up into smaller irregularly shaped twin fragments. Slip band extrusions occur also, in pure α-titanium. Surface crack topography produced in fatigued pure α-titanium consists of: (1) cracks at the twin interfaces. (2) a large number of cavities spanning the interface between the twin and the parent matrix. (3) cracks at the end of the thin twin. (4) cracks at the intersection of twins. (5) cracks at the grain boundary which is the dead end of the twin. (6) cracks in the twins. (7) formation of the catities in the persistent slip bands and their linkage. (8) cracks at the extrusions and intrusions.