On strain ageing and the fatigue limit

Abstract

Metallographic evidence, provided by a low-carbon steel that was strain-cycled under varying conditions of strain ageing, has shown that active fatigue slip-bands are kept narrow when strain ageing is rapid but, in general, dislocations within the active bands are not captured by solute-locking. It is concluded that, near room temperature, strain ageing must promote fatigue strength by strengthening the fatigue-hardened material that surrounds regions of strain concentration, so that the spread of fatigue damage is inhibited.