TC4 ELI钛合金显微组织对低周疲劳性能的影响

Low cycle fatigue behavior of TC4 ELI titanium alloy with bimodal and lamellar microstructure has been investigated by analysis of strain-cycles curve with different stress amplitudes. Results indicate that the volume fraction of equiaxed α phase is ~26.6% for the bimodal microstructure, and the average grain size is approximate 7.8 μm. At the same time, the thickness of α phase layer is about 0.5~2.0 μm for lamellar microstructure. Cyclic softening phenomenon is observed for all the samples of TC4 ELI alloys with different microstructures at the maximum stress. Sample with bimodal microstructure exhibits higher low cycle fatigue life, which could be attributed to the shorter effective slip path than the one with lamellar microstructure. More than that, the presence of equiaxed α-phase with high dislocation density could also hinder the initiation and propagation of fatigue cracks for the bimodal microstructure. Fracture morphology is flat and smooth for the sample with bimodal microstructure; however, some geometric facets associated with the original coarse-grained β are found for the sample with lamellar microstructure.