DWELL-SENSITIVE FATIGUE UNDER BIAXIAL LOADS IN THE NEAR-ALPHA TITANIUM-ALLOY IMI685
DWELL-SENSITIVE FATIGUE UNDER BIAXIAL LOADS IN THE NEAR-ALPHA TITANIUM-ALLOY IMI685
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DOI：
10.1016/0142-1123(94)90194-5
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发表时间：
1994-10-01
影响因子：
6
通讯作者：
BACHE, MR
中科院分区：
文献类型：
--
作者：
EVANS, WJ;BACHE, MR
低温驻留灵敏度是近α钛合金的一个工业相关问题。有充分的证据表明，当疲劳循环包含峰值应力停留期时，这些材料中的组件可以显示超过一个数量级的寿命减少。尽管做了大量的工作，但造成这种现象的机制尚未完全理解，尽管在厚截面中排列不良的α微观结构、塑性应变积累、氢水平和应力双轴性都被调用。研究方案解决了这个问题，把重点放在作为这类材料的典型代表的IMI685上。为了探究其中的机理，采用了张力和扭转加载模式，氢气浓度在20-60 ppm范围内变化。准解理小面形成是破坏过程的重要组成部分，本文介绍了在拉、扭转试样中近似垂直于主拉应力方向的基面上产生准解理小面的模型。在此模型的基础上，大部件的寿命衰减可能与先前β晶粒尺寸的变化有关。氢含量对变形响应有影响，但对破坏过程影响不显著。
Low-temperature dwell sensitivity is an industrially relevant problem in the near-alpha titanium alloys. It is well documented that components in these materials can display life reductions of over an order of magnitude when the fatigue cycle contains a dwell period at peak stress. Despite much work, the mechanisms responsible for the phenomenon are not understood in full, although a poorly aligned alpha microstructure in thick sections, plastic strain accumulation, hydrogen level and stress biaxiality have all been invoked. The research programme has addressed the problem by focusing on IMI685 as a typical representative of this class of material. To probe the mechanisms involved, tension and torsion loading modes were employed and hydrogen concentration was varied in the range 20-60 ppm. Quasi-cleavage facet formation is an essential element of the failure process and a model for its occurrence on basal planes approximately perpendicular to the principal tensile stress direction in both tension and torsion specimens is introduced. On the basis of this model, the life decrement in large components can be related to variations in prior beta grain size. Hydrogen content is shown to have an effect on deformation response but not a significant influence on the failure process.