摘要
为研究新一代高Nb含量γ-TiAl合金在低周疲劳过程中双态组织稳定性对应力-应变响应和疲劳断裂过程的影响,测试了Ti-47Al-5Nb合金在总应变控制条件下550℃～750℃温度范围的低周疲劳性能,并观察了循环变形后的显微组织,缺陷特征和断口形貌。结果表明:在550℃变形时所产生的循环硬化缘于不均匀的位错滑移,在滑移带内高密度位错之间产生强烈的相互作用降低了位错的可移动性,滑移带产生的应力集中使裂纹易于沿α2/γ片层界面扩展。在650℃和750℃变形时的循环软化则一方面归因于部分α2片层溶解和γ相再结晶,另一方面大量孪晶的激活和位错通过交滑移和攀移克服短程障碍的作用使合金的变形能力提高,同时增加了疲劳过程中的塑性应变累积。疲劳断口特点为等轴γ晶和α2/γ片层的穿晶断裂。
To investigate the microstructural stability, stress-strain response and fatigue fracture of a new generation γ-TiAl alloy with high Nb content under cyclic deformation, Low aycle fatigue tests under total strain controlling were carried out in the temperature range of 550℃-750℃ Deformed microstructures and fatigue fracture surfaces were observed. The cyclic hardening at 550℃ is attributed to the nonuniform dislocation slip. The strong interaction among dislocations reduces the removability of dislocations. The slip bands within y lamellae produce stress concentration at γ/α2 interface, leading to an interlamellar fracture. The cyclic softening at 650℃ and 750℃ results from the dissolution of α2 lamellae and the recrystallization of yphase. The activation of deformation twins and the occurrence of cross slip and the climb of dislocations increase the deformability of the matrix and promote the plastic strain accumulation during fatigue process. The fracture surfaces exhibit a transgranular and translamellar fracture.
出处
《稀有金属材料与工程》
SCIE
EI
CAS
CSCD
北大核心
2006年第9期1359-1362,共4页
Rare Metal Materials and Engineering
基金
教育部留学归国人员启动基金资助
