Transient Stress Concentration in Diffusional Creep of a Thin Foil with Heterogeneous Grain Boundary Diffusivity
Transient Stress Concentration in Diffusional Creep of a Thin Foil with Heterogeneous Grain Boundary Diffusivity
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DOI：
10.1177/1081286508092610
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发表时间：
2009-01
影响因子：
2.6
通讯作者：
T. Bhandakkar;Y. Wei;H. Gao
中科院分区：
文献类型：
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作者：
T. Bhandakkar;Y. Wei;H. Gao
研究了具有异质晶界扩散率和非均匀晶粒尺寸的薄膜中的Coble蠕变，模型为具有高扩散率的晶界与不等长的低扩散率的晶界连接的薄箔在远场单轴拉伸应力作用下的蠕变。结果表明，在高扩散率边界的特征时间尺度上，在GB结附近出现一个瞬态应力峰，在低扩散率边界的特征时间尺度上，当系统达到稳态时，应力峰消失.我们表明，对于一个给定的GB的尺寸比，这种应力取决于几何上的GB扩散率比。基于GB的扩散率和尺寸比，我们提出了一个图划分的制度，其中峰值应力是由稳态解和瞬态应力解确定。
Coble creep in thin films with heterogeneous grain boundary (GB) diffusivity and non-uniform grain size is investigated in the model problem of a thin foil with a high diffusivity GB joined with a low diffusivity GB of unequal length and subjected to a far field uniaxial tensile stress. It is found that a transient stress peak emerges near the GB junction on the characteristic time scale of the high diffusivity boundary and then disappears when the system reaches steady-state on the characteristic time scale of the low diffusivity boundary. We show that for a given GB size ratio, this stress depends logarithmically on the GB diffusivity ratio. Based on the GB diffusivity and size ratios, we present a diagram demarcating the regime in which peak stress is determined by the steady state solution and that determined by the transient stress solution.