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Fatigue Crack Growth Mechanisms in HCP Single Crystals

HCP 单晶的疲劳裂纹扩展机制

基本信息

批准号：
11650715
负责人：
TAKASHIMA Kazuki
金额：
$ 2.43万
依托单位：
TOKYO INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650715/
关键词：
Titanium Single Crystal Fatigue Crystallographic Orientation Crack Growth Rate Crack Growth Mechanism Slip System Twinning HCP金属疲労き裂伝播分子動力学

项目摘要

There have been few studies on fatigue crack growth mechanisms in HCP crystals. This may be partly due to the fact that the slip systems of HCP crystals have often not yet been identified precisely. In addition, mechanical twinning may occur in HCP crystals to accommodate deformation, since the number of slip systems in HCP metals is limited. This may also make it difficult to clarify fatigue crack growth mechanisms in HCP metals. Among HCP crystals, a-titanium and its alloys have been applied to aerospace structures and engine components because of their excellent specific strength and corrosion resistance. Therefore, it is important to address fundamental mechanisms in such materials. In this investigation, the fatigue crack growth behavior of a-titanium single crystals has been investigated in laboratory air at room temperature. Two types of CT specimens E and F with different notch orientations were prepared. In the E- and the F-specimens, the notch plane was (0001), and the notch directions were [1010] and [2110], respectively. The crack propagates roughly parallel to the basal plane in both the E- and the F-specimens, and the traces which correspond to {1012} twin systems are found near the crack plane. Ridges parallel to <1010>, and traces and bands due to {1012} twinning are observed on the fatigue surfaces. These results suggest that the crack growth might occur plausibly by the activation of micro-twins.

目前对HCP晶体中疲劳裂纹扩展机理的研究还很少。这可能部分是由于HCP晶体的滑移系通常还没有被精确地识别。此外，由于HCP金属中滑移系的数量有限，HCP晶体中可能发生机械孪生以适应变形。这也可能使其难以澄清HCP金属中的疲劳裂纹扩展机制。在HCP晶体中，α-钛及其合金由于其优异的比强度和耐腐蚀性而被应用于航空航天结构和发动机部件。因此，重要的是解决这些材料中的基本机制。本文研究了α-钛单晶在室温空气中的疲劳裂纹扩展行为。制备了两种不同切口方向的CT试样E和F。在E-和F-试样中，缺口平面为（0001），缺口方向分别为[1010]和[2110]。在E-和F-试样中，裂纹大致平行于基面扩展，并且在裂纹面附近发现对应于{1012}孪晶系统的痕迹。在<1010>疲劳表面上观察到平行于{1012}孪晶的脊、痕迹和条带。这些结果表明，裂纹扩展可能是由于微孪晶的激活而发生的。