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A model for creep based on microstructural length scale evolution

机译：基于微结构长度尺度演化的蠕变模型

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This paper seeks to quantitatively link recovery and plastic deformation to develop a model for creep. A simple approach with one length scale coarsening equation is postulated in this paper to provide a descriptive and unified framework to understand recovery. We propose that recovery is a general dislocation-level coarsening process whereby the length scale, λ, is refined by dislocation generation by plastic deformation and is increased concurrently by coarsening processes. Coarsening relations generally take the form: d(λ~(mc)) = KR(T)dt where R(T) is the rate equation for the fundamental rate controlling step in coarsening, K a free constant, dt a time increment and m_c is the coarsening exponent. Arguments are presented that m_c should be in the range of 3-4 for dislocation or subgrain coarsening. The coarsening equation postulated is consistent with the compared data sets in the following ways: (ⅰ) temporal evolution of one length scale λ; (ⅱ) temperature dependence of recovery rate; (ⅲ) adequacy of single parameter in the proper description of strength change. The coarsening equation is coupled with standard arguments for modeling plastic deformation. Combining these we can easily justify the form of the empirically derived Dorn creep equation: γ/(D(T)) = B(τ/μ)~n where the mobility of the recovering feature, R(T) should typically scale with self diffusivity, D(T), and the value of the steady-state creep exponent, n is 2 + m_c — 2c where c is a constant related to dislocation generation that should be in the range of 0-0.5. Hence, this approach predicts creep as being controlled by self diffusion and that the steady-state stress exponent should be on the order of 4-6. All the parameters in the creep model can be estimated from non-creep data. Comparison with the reported steady-state creep data of pure metals shows good agreement suggesting recovery modeled as coarsening is a fundamental element in steady-state creep.
机译：本文试图定量地将恢复和塑性变形联系起来，以建立蠕变模型。本文提出了一种使用一个长度尺度粗化方程的简单方法，以提供一个描述性和统一的框架来理解回收率。我们提出恢复是一般的位错级粗化过程，其中长度尺度λ通过塑性变形通过位错产生而得到细化，并通过粗化过程同时增加。粗化关系通常采用以下形式：d（λ〜（mc））= KR（T）dt其中，R（T）是粗化中基本速率控制步骤的速率方程，K是自由常数，dt是时间增量，m_c是粗化指数。提出了关于位错或亚晶粒粗化的m_c应在3-4的范围内的论点。假设的粗化方程在以下方面与比较的数据集一致：（ⅰ）一个长度尺度λ的时间演化； （ⅱ）温度对回收率的依赖性； （ⅲ）正确描述强度变化时单个参数是否足够。粗化方程式与用于模拟塑性变形的标准参数结合在一起。结合这些，我们可以很容易地证明经验得出的Dorn蠕变方程的形式：γ/（D（T））= B（τ/μ）〜n其中，恢复特征的迁移率R（T）通常应随自身成比例扩散率D（T）和稳态蠕变指数的值n为2 + m_c_2c，其中c是与位错生成有关的常数，应在0-0.5的范围内。因此，该方法预测蠕变受自扩散控制，并且稳态应力指数应在4-6的数量级上。蠕变模型中的所有参数都可以根据非蠕变数据进行估算。与已报道的纯金属稳态蠕变数据进行比较，表明吻合良好，表明以粗化为模型的回收率是稳态蠕变的基本要素。

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