Microstructure evolution during severe plastic deformation
Microstructure evolution during severe plastic deformation
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DOI：
10.1080/14786435.2011.615349
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发表时间：
2011-01-01
影响因子：
1.6
通讯作者：
Wilde, Gerhard
中科院分区：
文献类型：
--
作者：
Divinski, Sergiy V.;Padmanabhan, K. A.;Wilde, Gerhard
放射性示踪剂对严重变形、超细晶材料的扩散研究揭示了超快速传输路径的存在，包括“非平衡”晶界和自由体积。在某些实验条件下，即使在纯铜中也会产生渗透孔隙。当局部最大剪切应力超过剪切屈服应力时，金属就会形成微裂纹。然而，由于金属的延展性、应力系统的流体静力成分和/或动态恢复/再结晶，它们的生长和扩展被推迟到变形过程的后期。换句话说，只有当进一步变形的范围受到高度限制时，才会出现裂纹的扩展和扩展。利用该方法预测了等通道角挤压所需的载荷、霍尔-佩奇图斜率随晶粒尺寸减小的变化以及金属在剧烈塑性变形过程中可达到的最小晶粒尺寸的理论极限，并通过实验结果进行了验证。实验成功地防止了由叠加静水压力的渗透裂缝的形成也说明了使用该模型。
Radiotracer diffusion studies of severely deformed, ultra-fine grained materials have revealed the presence of ultra-fast transport paths, which include "non-equilibrium" grain boundaries and free volume. Under some experimental conditions, percolating porosity is produced even in pure copper. Micro-cracks may form in metals, if the local maximum shear stress exceeds the shear yield stress. However, their growth and propagation is postponed till late in the deformation process owing to the ductility of metals, the hydrostatic component of the stress system and/or dynamic recovery/recrystallization. In other words, crack growth and propagation is present only when the scope for further deformation is highly restricted. Using this approach, the load required for equal channel angular pressing, the change in the slope of the Hall-Petch plot with decreasing grain size and the theoretical limit for the smallest grain size attainable in a metal in a severe plastic deformation process are predicted and validated by experimental results. Experimentally successful prevention of percolated crack formation by the superposition of a hydrostatic pressure is also accounted for using this model.