位移级联对钼铼单晶固溶体合金力学性能影响的分子动力学模拟研究

Molecular Dynamics Study on the Effects of Displacement Cascades on the Mechanical Properties of Molybdenum-Rhenium Single-Crystal Solid Solution Alloys

摘要:

钼铼合金因其高熔点、优异的高温力学性能和抗辐照特性,被认为是先进核反应堆燃料包壳和堆芯结构材料的重要候选材料。本工作采用分子动力学方法,通过与纯Mo单晶结果对比,系统研究了位移级联不同Re含量(5%和14%)的Mo-Re单晶固溶体合金力学性能的影响规律。研究结果表明,Re含量的增多会使MoRe单晶固溶体合金在拉伸应力下更多滑移系统启动,有效提高其塑性；位移级联则显著降低了Mo-Re单晶固溶体合金的拉伸强度和塑性,其底层的物理机制源于级联引入的缺陷诱发了局部的应力集中和能量变化,导致滑移系统启动的临界应力下降,加速材料屈服并降低单晶固溶体合金的均匀延伸率。本工作的研究结果揭示了位移级联对Mo-Re单晶固溶体合金拉伸力学性能的影响规律及其原子机制,对先进核反应堆材料的设计与选材具有科学参考价值。

Abstract:

Due to their high melting points, excellent high-temperature mechanical properties, and radiation resistance, molybdenum-rhenium (Mo-Re) alloys have been considered as primary candidates for fuel cladding and core structural materials used in advanced nuclear reactors. In this study, molecular dynamics simulations were employed to systematically investigate the effects of displacement cascades on the mechanical properties of Mo-Re single-crystal solid-solution alloys with different Re contents (5% and 14%), using pure Mo single crystals as a benchmark. The results indicate that increasing the Re content could activate more slip systems within the Mo-Re single-crystal solid-solution alloys under tensile stress, thereby effectively enhancing their plasticity. Results further indicated that displacement cascades could significantly degrade both the tensile strength and plasticity of the Mo-Re alloys. The underlying physical mechanism may be from the defects introduced by the cascades, which can induce localized stress concentrations and energy perturbations, resulting in a reduction in the critical stress required to activate slip systems, thereby accelerating material yielding and decreasing the uniform elongation of the single-crystal solid-solution alloys. Therefore, the results of this study elucidate the influence of displacement cascades on the tensile mechanical properties of Mo-Re single-crystal solid-solution alloys, as well as the underlying atomic-scale mechanisms, providing valuable scientific insights for the design and selection of materials for advanced nuclear reactors.