Slip Activity During Low-Stress Cold Creep Deformation in a Near-Α Titanium Alloy
Slip Activity During Low-Stress Cold Creep Deformation in a Near-Α Titanium Alloy
复制标题
近α钛合金低应力冷蠕变变形过程中的滑移活动
DOI：
--
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
M. Preuss
中科院分区：
文献类型：
--
作者：
Claudius Dichtl;D. Lunt;M. Atkinson;R. Thomas;Adam Plowman;Bartosz Barzdajn;R. Sandala;J. Q. da Fonseca;M. Preuss
众所周知，近α钛合金容易受到冷保压疲劳（CDF）的影响，这是一种与高载荷保压时间叠加在低周疲劳载荷期间的冷蠕变有关的失效机制。为了揭示冷保压期间的变形机制并更好地理解微观结构的作用，在低于0.2%的屈服应力的应力水平下，使用晶粒取向图和原位电子显微镜成像的组合，研究了TIMETAL®834的两种不同的双峰微观结构（精细和粗糙转变产物）。这使得深入分析的二维滑移模式和滑移系统的活动，使用高分辨率数字图像相关（HRDIC），显示在这两个微观结构的基础滑移最初是主导滑移模式之前，棱柱滑移活动增加接近0.2%的屈服应力。比较双峰显微组织中的两种成分，第一滑移带主要位于初生α晶粒中，表明次生α菌落的强度较高，特别是对于较细的转变产物。在10分钟的负荷保持在低于0.2%的屈服应力的应力，更多的塑性应变和更长的连接的几个晶粒之间的滑移痕迹中观察到的样品与粗的转变产品，表明更高的敏感性冷蠕变变形。
Near-α titanium alloys are known to be susceptible to cold dwell fatigue (CDF), a failure mechanism that has been linked to cold creep during high-load dwell times superimposed onto low cycle fatigue loading. In order to shed new light on the deformation mechanisms during cold dwell and to understand better the role of the microstructure, two different bimodal microstructures (fine and coarse transformation product) of TIMETAL®834 were investigated at stress levels below the 0.2% proof stress using a combination of grain orientation mapping and in-situ electron microscopy imaging. This enabled in-depth analysis of 2D slip patterns and slip system activity using High-Resolution Digital Image Correlation (HRDIC), showing that in both microstructures basal slip is initially the dominant slip mode before prismatic slip activity increases approaching the 0.2% proof stress. Comparing the two constituents in the bimodal microstructure, first slip bands are localised predominantly in primary α grains, indicating higher strength of secondary α colonies, particularly for finer transformation products. During 10-minute load holds at stresses below 0.2% proof stress, more plastic strain and longer connected slip traces across several grains were observed in the sample with coarse transformation product, indicating higher susceptibility to cold creep deformation.