α相对高强韧Ti-55531合金强化及断裂机制的影响

In order to find the influence of α phase on tensile fracture behavior of high strength-toughness Ti-55531 alloy, different heat treatments and analysis methods including SEM, OM and XRD were adopted. Results show that the content of secondary α phase in bimodal microstructures is increased and the scale becomes finer with decreasing of content and scale of primary α phase, so that the strength of alloy increases and ductility decreases. In lamellar microstructures, with coarsening of secondary α phase, both strength and ductility of the alloy are decreased. In full β microstructures, alloys get well in ductility but bad in strength. Both fracture modes of bimodal and lamellar microstructures are mixed modes including transgranular cleavage, microvoid accumulations and intergranular crack fracture. With decreasing of content and scale of primary α phase, the content of secondary α phase increases and the scale is coarsened, the percentage of microvoid accumulations fracture is decreased while percentage of transgranular cleavage and intergranular crack fracture is increased.