Akio Ishii Department of Mechanical Science and Bioengineering, Osaka University, Osaka, Japan.
PLoS One. 2013 Apr 11;8(4):e60586. doi: 10.1371/journal.pone.0060586. Print 2013.
Dislocation pipe diffusion seems to be a well-established phenomenon. Here we demonstrate an unexpected effect, that the migration of interstitials such as carbon in iron may be accelerated not in the dislocation line direction ξ, but in a conjugate diffusion direction. This accelerated random walk arises from a simple crystallographic channeling effect. c is a function of the Burgers vector b, but not ξ, thus a dislocation loop possesses the same everywhere. Using molecular dynamics and accelerated dynamics simulations, we further show that such dislocation-core-coupled carbon diffusion in iron has temperature-dependent activation enthalpy like a fragile glass. The 71° mixed dislocation is the only case in which we see straightforward pipe diffusion that does not depend on dislocation mobility.
位错管扩散似乎是一个既定的现象。在这里，我们展示了一个意想不到的效果，即在铁中，间隙原子（如碳）的迁移可能不是沿着位错线方向 ξ 加速，而是沿着共轭扩散方向加速。这种加速的随机行走源于简单的晶体学通道效应。c 是柏氏矢量 b 的函数，但不是 ξ，因此位错环在任何地方都是相同的。使用分子动力学和加速动力学模拟，我们进一步表明，铁中位错核耦合的碳扩散具有类似于脆性玻璃的温度相关激活焓。只有在 71°混合位错的情况下，我们才看到不依赖于位错迁移率的直接位错管扩散。
