Fatigue Fracture Mechanisms of Titanium Alloy at Cryogenic Temperature

钛合金低温疲劳断裂机理

• 批准号: 02650057
• 负责人: KATAGIRI Kazumune
• 金额: $ 1.15万
• 依托单位: Iwate University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1990
• 资助国家: 日本
• 起止时间: 1990 至 1991
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02650057/
• 关键词: Titanium Alloy; Fatigue Mechanisms; Cryogenic Temperature; Fatigue Crack; Crack Closure; Fracture Surface; 疲労破壊; き裂伝ぱ速度; き裂開閉口; き裂経路; 破面観察; 微視組織

The fatigue crack initiation and growth mechanisms of Ti-6Al-4V alloy at 77K were investigated. Measurement relevant to the crack growth as well as observations on the specimen surface, longitudinal section as well as fracture surface through optical microscope, SEM and high voltage TEM revealed the following results. 1)Crack was initiated in the surface alpha-grain at 77K. No subsurface crack initiation was observed in the 10^5 cycles life time stressing. 2)The fatigue crack growth rate at 77K is lower by factors of 1/2-1/4 as compared with that at 293K. The difference in the growth rate is larger at low growth rate region. The crack closure revel at 77K is higher than that at 300K through all the growth rates measured. The crack growth rate at 77K and 293K coincided to each other as a paramer of effective DELTAK. 3)Marked bifurcation of crack was observed at low growth rate in 77K fatigue. 4)The fracture surface in the low growth rate was consisted of facets of fine alpha-grain and it changed into plateaus as the growth rate increased. The fracture surface at 77K was rather flat as compared with that at 293K. Other than striations, as another difference in the fracture surface, facets elongated in the growth direction like "flute" observed in corrosion cracking was observed at 77K in the high growth rate region. 5)Arrays of dislocation in the prismatic slip plane in alpha-grain were observed in region remote from a crack tip which is growing at low rate.

研究了77K时TI-6AL-4V合金的疲劳裂纹启动和生长机制。与裂纹生长以及通过光学显微镜，SEM和高电压TEM上的试样表面，纵向截面以及骨折表面的观测相关的测量结果显示了以下结果。 1）在77K的表面α粒中启动裂缝。在10^5周期的寿命时，未观察到地下裂纹开始。 2）与293K相比，疲劳裂纹在77K时的疲劳裂纹增长率较低。在低生长速率区域，生长速率的差异更大。通过测量的所有增长率，在77K处的裂纹封闭距离高于300K的裂纹。 77K和293K处的裂纹增长速率彼此相吻合，这是有效的Deltak的参数。 3）在77K疲劳中以低生长速率观察到裂纹的明显分叉。 4）低生长速率中的断裂表面由细α粒的方面组成，随着生长速度的增加，它变成了高原。与293K相比，在77K处的断裂表面相当平坦。除条纹以外，作为断裂表面的另一个差异，在高生长速率区域的77K处观察到在腐蚀裂纹中观察到的“长笛”的面孔在生长方向上伸长。 5）在远离裂纹尖端的区域中观察到α粒的棱柱滑移平面中的位错阵列，该区域以低速率生长。

项目成果

K.Katagiri: "Fatigue Crack Growth in Metastable Austenitic Stainless Steel at Cryogenic Temperatures" Advance in Cryogenic Engineering,Materials Eds.R.P.Reed and F.R.Fickett,Plenum Press NY. 36. 1225-1232 (1990)

K.Katagiri：“低温下亚稳态奥氏体不锈钢的疲劳裂纹扩展”低温工程进展，材料 Eds.R.P.Reed 和 F.R.Fickett，Plenum Press NY。

片桐 一宗: "チタン合金の極低温疲労破面" 低温工学. 27. (1992)

Kazumune Katagiri：“钛合金的低温疲劳断裂表面”，低温工程27。（1992）

K. Katagiri, H. Kaneshiro, H. Mori and M. Ishii: "Dislocation Structures of Strain Localized Region and Fatigue Crack Initiation in Metals and Alloys" Proc. 3rd Int. Conf. Residual Stresses, Elsevier Applied Science, Essex. (1992)

K. Katagiri、H. Kaneshiro、H. Mori 和 M. Ishii：“金属和合金中应变局部区域的位错结构和疲劳裂纹萌生”Proc。

K. Katagiri, M. Tsuji, T. Okada, N. Komabayashi, Y. Shoji: "Fracture Surface of Titanium Alloy Fatigued at Cryogenic Temperature" Cryogenic Engineering. 27. (1992)

K. Katagiri、M. Tsuji、T. Okada、N. Komabayashi、Y. Shoji：“低温疲劳钛合金断裂表面”低温工程。

K.Katagiri: "Dislocation Structures of Strain Localized Region and Fatigue Crack Initiation in Metals and Alloys" Proc.3rd Int.Conf.Residual Stresses Elsevier Applied Science,Essex. (1992)

K.Katagiri：“金属和合金中应变局部区域的位错结构和疲劳裂纹萌生”Proc.3rd Int.Conf.Residual Stresses Elsevier Applied Science，埃塞克斯。