α相对高强韧Ti-55531合金强化及断裂机制的影响

Influence of α phase on strengthen and fracture mechanisms of high strength-toughness Ti-55531 alloy

摘要:

采用SEM、OM及XRD等分析方法,结合不同的热处理工艺,系统分析了α相的形态、含量及尺寸等特征参数对高强韧Ti-55531合金强化及断裂机制的影响。结果表明：双态组织,随等轴α_p含量降低,尺寸减小,次生片层α_s含量增多,长度变长,宽度更窄；导致合金的强度提高,塑性降低。片层组织,随次生α_s片层的粗化,合金强度和塑性都下降。全β晶粒组织,强度较低,塑性很好。双态和片层组织Ti-55531合金的断裂方式均为穿晶解理、微孔聚集型和沿晶开裂的混合断裂机制；随α_p含量降低和尺寸减小,α_s含量和尺寸增加,微孔聚集断裂数量降低,穿晶解理和沿晶开裂特征数量增加。

Abstract:

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 are adopted. Results show that the content of secondary α phase in bimodal microstructures are increased and the scale became finer, with decreasing of content and scale of primary α phase, so that the strength of alloy are increased and ductility are decreased. In lamellar microstructures, with coarsening of secondary alpha 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 mix modes including transgranular cleavage, microvoid accumulations and intergranular crack fracture. As decreasing of content and scale of primary α phase, the content of secondary α phase are increased and the scale are coarsen, the percentage of microvoid accumulations fracture are decreased and percentage of transgranular cleavage and intergranular crack fracture are increased.