Stress driven creep deformation and cavitation damage in pure copper
Stress driven creep deformation and cavitation damage in pure copper
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DOI：
10.1016/j.msea.2021.142543
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发表时间：
2021-12
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通讯作者：
Yadunundan Das;A. Fernández-Caballero;E. Elmukashfi;H. Jazaeri;A. Forsey;M. Hutchings;R. Schweins;P. Bouchard
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作者：
Yadunundan Das;A. Fernández-Caballero;E. Elmukashfi;H. Jazaeri;A. Forsey;M. Hutchings;R. Schweins;P. Bouchard
采用单向拉伸的扁沙漏试样，研究了纯铜在250° C下的蠕变和空泡损伤的应力依赖性。原位数字图像相关（DIC）是用来监测随时间变化的表面蠕变变形，非原位小角中子散射（SANS）适用于测量体积空化损伤，和扫描电子显微镜用于表面表征。应用自洽弥散模型成功地解释了DIC测量的全场多应力蠕变变形行为。通过近似一系列形状的空腔与球形空隙的模型分布，最小稳定的空腔成核直径范围为600至1200 μ m，这取决于所施加的应力水平，在SANS结果中清楚地观察到。这一发现支持经典的表面能/功平衡表达式定义的最小稳定腔的大小的有效性。在中断寿命样品中观察到的所有空洞本质上都是小面的。SANS的数据意味着连续的空腔成核和生长在整个蠕变寿命，与成核率在应力小于100 MPa线性相关的蠕变速率。这与Sandström和Wu [1]的双台阶晶界滑动形核模型一致。
The stress dependence of creep deformation and cavitation damage in pure copper at 250° C under uniaxial loading is studied using a flat hourglass test specimen under uniaxial tensile load. In-situ digital image correlation (DIC) is used to monitor time dependent surface creep deformation, ex-situ small angle neutron scattering (SANS) applied to measure volumetric cavitation damage, and scanning electron microscopy used for surface characterisation. A self-consistent discolation model is successfully applied to explain the full field multi-stress creep deformation behaviour measured by DIC. Through approximating a range of shaped cavities with a model distribution of spherical voids, a minimum stable cavity nucleation diameter range of 600 to 1200 Å, depending on the applied stress level, is clearly observed in the SANS results. This finding supports the validity of the classical surface energy/work balance expression defining the minimum stable cavity size. All cavities observed in interrupted life samples were facetted in nature. The SANS data imply continuous cavity nucleation and growth throughout creep life, with a nucleation rate at stresses less than 100 MPa linearly related to the creep rate. This is in accordance with the double ledge grain boundary sliding nucleation model of Sandström and Wu [1].