Low Cycle Fatigue Behavior of TC21 Titanium Alloy with Bi-Lamellar Basketweave Microstructure

Abstract

Low cycle fatigue (LCF) behaviors of TC21 alloy with a bi-lamellar basketweave microstructure were investigated in this paper. The strain fatigue tests were carried out at total strain amplitudes of 1.4% to 2.0%. The cyclic stress response showed the cyclic softening behavior. In addition, the shape of the hysteresis rings exhibited a non-Masing model behavior. The cyclic stress–strain as well as the strain-life equations were obtained. The fatigue life decreased significantly with an increasing total strain from 1.4% to 2.0%. The cyclic softening behavior was interpreted by cyclic back stress and friction stress. Low cycle fatigue cracks were predominantly initiated on the surface of the samples. The relationship between the fatigue sub-critical crack and microstructure was also discussed. The cyclic deformation behavior and crack initiation mechanism were revealed on the basis of the deformation microstructure under different strain amplitudes.