One-Dimensional Glide Motion of “Naked” Nanoscale 1/2^|^lt;111^|^gt; Prismatic Dislocation Loops in Iron

Abstract

One-dimensional (1D) glide diffusion of interstitial-type prismatic dislocation loops is believed to play key roles in microstructural evolutions within nuclear-fusion and fission materials upon energetic particle irradiation. In the present study, using in-situ transmission electron microscopy, we have examined behaviors of nanoscale 1/2<111> loops in high-purity α-iron at "low temperatures" ranging from 15 to 290 K, under zero external stress. We observed 1D intermittent and fast motion of loops above approximately 100 K, which was significantly different from the 1D continuous and viscous motion observed at "high temperatures" above approximately 450 K. The estimated lower-limit values of diffusivities for "low temperatures" were considerably higher than the values obtained through the extrapolation of the temperature dependence of the diffusivities at "high temperatures." These results support the idea that strong obstacles for loop motion are formed by heating of the specimens to "high temperatures" after the introduction of loops.

Rearrangement of interstitial defects in alpha-Fe under extreme condition

“…Indeed, transmission electron microscopy (TEM) observations in bcc transition metals reveal the existence of planar loops. They can have the Burgers vector aligned along either ½<111> (highly mobile) or <100> (immobile), depending on temperature [16,17,18,19,12]. Dislocation loops with ½<111> Burgers vector are dominant in most bcc metals, and are therefore presumed to be the most stable configurations for bundling crowdions.…”

Interaction between interstitial carbon atoms and a ½ 〈1 1 1〉 self-interstitial atoms loop in an iron matrix: a combined DFT, off lattice KMC and MD study

“…energy along the 〈1 1 1〉 direction [1] in pure Fe thus making it a mobile defect which can easily interact with other defects, as presented in the mechanism proposed by Xu et al leading to the formation of 〈1 0 0〉 loops by the interaction between two ½ 〈1 1 1〉 loops [2]. While the very mobile 〈1 1 1〉 loops may migrate to grain boundaries, the almost immobile 〈1 0 0〉 loops are expected to accumulate in the microstructure and act as sinks for mobile defects [2] and may as well hinder the dislocations movement.…”

<110> Dislocation Junction Formation via the Coalescence between Nanoscale 1/2<111> Prismatic Dislocation Loops in Iron

“…In α-iron, it has been revealed by molecular dynamics (MD) simulations [5][6][7][8][9] and in-situ TEM experiments, [10][11][12] nanoscale interstitial-type prismatic dislocation loops with b = 1/2 < 111 > undergo one-dimensional (1D) glide diffusion (Brownian motion) along their b directions by thermal energy even in the absence of stresses. Two 1D migrating 1/2 < 111 > loops with different b values and intersecting glide cylinders can collide with each other, via attractive elastic interaction, 13) which has been shown by MD simulations [14][15][16][17] and an in-situ TEM experiment.…”