Mapping dislocation densities resulting from severe plastic deformation using large strain machining
Mapping dislocation densities resulting from severe plastic deformation using large strain machining
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DOI：
10.1557/jmr.2018.264
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发表时间：
2018-08
影响因子：
2.7
通讯作者：
Sepideh Abolghasem;S. Basu;S. Shekhar;M. Ravi Shankar
中科院分区：
文献类型：
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作者：
Sepideh Abolghasem;S. Basu;S. Shekhar;M. Ravi Shankar
位错的增殖决定了塑性变形过程中微观结构演变的轨迹。人们已经认识到，位错储存和变形驱动的亚晶粒形成是相关的——相似性原理，即位错密度（ρ_i）与亚晶粒尺寸（δ）自相似地成比例：$(\delta):\delta \sqrt {{\rho _{\rm{i}}}} \sim$ ∼常数。在此，利用在一系列剧烈剪切变形条件下（应变范围为1 - 10，应变速率为10 - 10³/秒）的大应变加工，对这一概念在铜中的稳健性进行了探究。变形应变、应变速率和温度特性与电子显微镜分析相结合，并且通过对晶体学平面的X射线衍射峰展宽进行量化来测量位错密度。我们将位错密度的变化参数化为应变以及速率参数R的函数，R是应变速率、温度和材料常数的函数。我们证实了在热机械条件的数量级范围内，位错密度和亚晶粒结构之间的相似性保持不变。
The multiplication of dislocations determines the trajectories of microstructure evolution during plastic deformation. It has been recognized that the dislocation storage and the deformation-driven subgrain formation are correlated—the principle of similitude, where the dislocation density (ρ_i) scales self-similarly with the subgrain size (δ): $(\delta):\delta \sqrt {{\rho _{\rm{i}}}} \sim $ ∼ constant. Here, the robustness of this concept in Cu is probed utilizing large strain machining across a swathe of severe shear deformation conditions—strains in the range 1–10 and strain-rates 10–10^3/s. Deformation strain, strain-rate, and temperature characterizations are juxtaposed with electron microscopy, and dislocation densities are measured by quantification of broadening of X-ray diffraction peaks of crystallographic planes. We parameterize the variation of dislocation density as a function of strain and a rate parameter R , a function of strain-rate, temperature, and material constants. We confirm the preservation of similitude between dislocation density and the subgrain structure across orders-of-magnitude of thermomechanical conditions.