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首页> 外文期刊>Metallurgical and Materials Transactions, A. Physical Metallurgy and Materials Science >The Contribution of Dislocation Density and Velocity to the Strain Rate and Size Effect Using Transient Indentation Methods and Activation Volume Analysis
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The Contribution of Dislocation Density and Velocity to the Strain Rate and Size Effect Using Transient Indentation Methods and Activation Volume Analysis

机译：使用瞬态压痕方法和激活体积分析脱位密度和速度对应变速率和尺寸效应的贡献

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Constant load indentation creep and load relaxation tests were performed on several FCC Al, Ag, and Ni metals that exhibit indentation size effect (ISE) to examine the coupled relationship between the activation volume V* at specific loads, the dislocation density rho, and the dislocation velocity (v) from kinetics-based perspective. The influence of the ISE on the dislocation velocity and the activation volume is thoroughly examined using the two independent indentation creep and load relaxation experiments. This study is carried out based on the general experimental and theoretical hypothesis that the ISE is driven by a dislocation mechanism, specifically the increase in the geometrically necessary dislocation density at shallow depth of indentation due to the presence of a large strain gradient. Geometrically necessary dislocations dominate the material's propensity to work harden when their density exceeds the density of statistically stored dislocations and are primarily considered responsible for the size effects observed in indentation. Based on the preestablished bilinear behavior and the decrease in the activation volume with hardening due to dislocation-dislocation interaction in indentation creep experiments by Elmustafa and Stone, 2003, we demonstrate that the dislocation velocity exhibits a bilinear behavior when plotted vs hardness using the Orowan's relation. Ag and Ni distinctively depict a bilinear behavior in the dislocation velocity with hardness, whereas Al exhibited a rather linear behavior. This can be explained by the fact that aluminum's work-hardening rate is higher due to the increase in the rate and intensity of cross-slip and dislocation climbing. (C) The Minerals, Metals & Materials Society and ASM International 2018
机译：在几种FCC AL，Ag和Ni金属上进行恒定载荷缩进蠕变和负载弛豫测试，其表现出凹口尺寸效应（ISE）来检查特定负载，位错密度Rho和脱位密度rho之间的活化体积V *之间的耦合关系。基于动力学的角度的位错速度（v）。使用两个独立的压痕蠕变和负载松弛实验，彻底检查ISE对位错速度和活化体积的影响。本研究基于一般的实验和理论假设进行，即ISE由位错机制驱动，特别是由于存在大应变梯度的存在而在浅凹陷中的几何必要位错密度增加。几何必要的脱位使材料占据了材料的倾向，当它们的密度超过统计储存的脱位密度时，主要被认为是对压痕中观察到的尺寸效应的负责。根据Elmustafa和Stone，2003年缩进蠕变实验中的凹陷蠕变实验中的脱位脱位相互作用的脱位脱位相互作用的活化体积减少，我们证明了使用Orowan的关系绘制了VS硬度时的位错速度表现出双线性行为。 AG和Ni明显地描绘了具有硬度的位错速度中的双线性行为，而Al表现出相当线性的行为。这可以通过铝的工作 - 硬化率较高的事实来解释，由于交叉滑移和脱位爬升的速率和强度的增加。 （c）2018年矿物质，金属和材料协会和ASM国际

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