Topography of fatigue fracture of two-phase titanium alloy

Abstract

1. Plastic deformation during cyclic loading of two-phase α+β titanium alloy, unlike the single-phase alloy, results from slip without twinning. 2. During fatigue failure of the α+β titanium alloy subjected to cyclic torsion the fatigue crack propagates in three stages — the initial stage consitsts of cleavage along slip planes under the influence of normal stresses; the intermediate stage consists of cleavage accompanied by considerable plastic deformation under the influence of shearing stresses; the final stage consists of quasibrittle fracture as the result of normal stresses. 3. Raising the temperature from −140 to +150°C changes the relationship between the areas of these zones — the area of the intermediate zone decreases and the area of the final zone increases substantially. The character of the zones themselves remains unchanged. 4. The increase in the fatigue life of the samples at low temperatures is affected by the initial stages of the process before the formation of the fatigue crack.