Solid-solution and precipitation softening effects in defect-free faceted Nickel-Iron nanoparticles
Solid-solution and precipitation softening effects in defect-free faceted Nickel-Iron nanoparticles
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DOI：
10.1016/j.actamat.2022.118527
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发表时间：
2022-11
期刊：
影响因子：
9.4
通讯作者：
Amit Sharma;O. Mendelsohn;A. Bisht;J. Michler;Raj Kiran Koju;Y. Mishin;E. Rabkin
中科院分区：
文献类型：
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作者：
Amit Sharma;O. Mendelsohn;A. Bisht;J. Michler;Raj Kiran Koju;Y. Mishin;E. Rabkin
众所周知，金属是通过添加合金或第二相的细小弥散析出物来强化的。在这里，我们表明，原始的，无缺陷的单晶镍纳米粒子与铁合金化导致了与直觉相反的软化，这是由于随机分布的溶质(Fe)原子和有序的Ni3Fe或富Fe相的纳米级沉淀。通过对沉积在蓝宝石衬底上的Ni-Fe双层薄膜进行固态除湿，制备了Fe含量为0-50at.%的Ni-Fe颗粒。Ni-27Fe和Ni-50Fe颗粒呈双峰分布，具有小的(111)和大的(100)取向。在所有颗粒中均观察到固溶体软化现象。(100)取向的Ni-27Fe颗粒具有均匀分布的有序Ni3Fe(L12)相，观察到析出软化现象。在高度合金化的Ni-50Fe颗粒表面和边缘附近发现了富Fe的析出物，导致了更大的软化。粒子形变的分子动力学模拟表明，软化效应与溶质原子随机分布引起的局部应力集中位错过早形核有关。这项工作说明了在无缺陷单晶金属纳米粒子中如何操纵甚至逆转在块体材料中工作的经典硬化机制，其塑性变形受位错成核控制。
It is well known that metals are strengthened by alloying additions or finely dispersed precipitates of a second phase. Here we show that alloying pristine, defect-free single crystalline nickel nanoparticles with iron results in a counter-intuitive softening due to randomly distributed solute (Fe) atoms and nano-size precipitates of the ordered Ni3Fe or Fe-rich phases. The Ni-Fe particles with Fe concentration of 0-50 at.% were synthesized by solid-state dewetting of Ni-Fe bilayer thin films deposited on a sapphire substrate. Ni-27Fe and Ni-50Fe particles exhibited a bimodal size distribution with small (111) and large (100) oriented particles. The solid solution softening was observed in all particles. The precipitation softening was observed in (100) oriented Ni-27Fe particles with uniformly distributed ordered Ni3Fe (L12) precipitates. Fe-rich precipitates were found on the surfaces and near the edges of the highly alloyed Ni-50Fe particles, leading to even greater softening. Molecular dynamic simulations of particle deformation have demonstrated that the softening effect is associated with premature dislocation nucleation at sites with a local stress concentration caused by the randomly distributed solute atoms. This work illustrates how the classical hardening mechanisms operating in bulk materials can be manipulated and even reversed in defect-free single-crystalline metal nanoparticles whose plastic deformation is controlled by dislocation nucleation.