Molecular dynamics study of solute strengthening in Al/Mg alloys
Molecular dynamics study of solute strengthening in Al/Mg alloys
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DOI：
10.1016/j.jmps.2005.12.008
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发表时间：
2006-08
影响因子：
5.3
通讯作者：
D. Olmsted;L. Hector;W. Curtin
中科院分区：
文献类型：
--
作者：
D. Olmsted;L. Hector;W. Curtin
采用分子动力学方法研究了Mg溶质原子对Al的强化作用。MD方法允许明确的“核心”效应，位错钉扎和减速，和位错unpinning热激活，所有下施加的负载。适当的MD模拟单元尺寸的选择进行评估，使用Labusch开发的分析概念。计算了单个Mg原子与直刃位错和螺形位错的相互作用能，并与连续介质模型进行了比较。使用单一的镁能量，一个一维的能量景观的运动直刃位错通过随机场的镁溶质计算。在这个景观中的最小值匹配以及在零温度下的MD模拟中发现的。解钉直刃位错的应力被困在由溶质产生的局部能量最小值，然后预测半解析使用的能量景观，并获得良好的协议与MD结果。在300和500 K的温度下，解钉扎的热激活速率与应力和温度的半解析计算，并与完整的MD结果再次获得与过渡态模型中的一个单一的尝试频率的拟合一致。的半解析模型的协议提供了一个基础，用于计算屈服应力与应变速率和温度，导致统计钉扎，对于一个单一的滑移系上的非相互作用的位错的情况下，并扩展分析，研究动态应变时效的影响所导致的镁原子周围的钉扎位错的扩散。
The strengthening of Al by Mg solute atoms is investigated using molecular dynamics (MD) studies of single dislocations moving through a field of randomly placed solutes. The MD method permits explicit treatment of “core” effects, dislocation pinning and deceleration, and dislocation unpinning by thermal activation, all under an applied load. Choice of an appropriate MD simulation cell size is assessed using analytic concepts developed by Labusch. The interaction energy of a single Mg atom with straight edge and screw dislocations is computed and compared with continuum models. Using the single Mg energies, a one-dimensional energy landscape for the motion of a straight edge dislocation through a random field of Mg solutes is computed. The minima in this landscape match well with those found in the MD simulations at zero temperature. The stress to unpin a straight edge dislocation trapped in a local energy minimum generated by the solutes is then predicted semi-analytically using the energy landscape, and good agreement is obtained with the MD results. At temperatures of 300 and 500K, the thermally activated rate of unpinning vs. stress and temperature is calculated semi-analytically, and agreement with the full MD results is again obtained with the fitting of a single attempt frequency in a transition state model. The agreement of the semi-analytical models provides a basis for calculating yield stress vs. strain rate and temperature, resulting from statistical pinning, for the case of non-interacting dislocations on a single slip system, and for extending the analysis to study dynamic strain aging effects resulting from diffusion of Mg atoms around a pinned dislocation.