Bisht Anuj, Koju Raj Kiran, Qi Yuanshen, Hickman James, Mishin Yuri, Rabkin Eugen
Department of Materials Science and Engineering, Technion-Israel Institute of Technology, Haifa, Israel.
Department of Physics and Astronomy, MSN 3F3, George Mason University, Fairfax, VA, USA.
Nat Commun. 2021 May 4;12(1):2515. doi: 10.1038/s41467-021-22707-x.
The classic paradigm of physical metallurgy is that the addition of alloying elements to metals increases their strength. It is less known if the solution-hardening can occur in nano-scale objects, and it is totally unknown how alloying can impact the strength of defect-free faceted nanoparticles. Purely metallic defect-free nanoparticles exhibit an ultra-high strength approaching the theoretical limit. Tested in compression, they deform elastically until the nucleation of the first dislocation, after which they collapse into a pancake shape. Here, we show by experiments and atomistic simulations that the alloying of Ni nanoparticles with Co reduces their ultimate strength. This counter-intuitive solution-softening effect is explained by solute-induced local spatial variations of the resolved shear stress, causing premature dislocation nucleation. The subsequent particle deformation requires more work, making it tougher. The emerging compromise between strength and toughness makes alloy nanoparticles promising candidates for applications.
物理冶金的经典范式是向金属中添加合金元素会提高其强度。对于固溶强化是否会在纳米尺度物体中发生鲜为人知，而合金化如何影响无缺陷多面体纳米颗粒的强度则完全未知。纯金属无缺陷纳米颗粒表现出接近理论极限的超高强度。在压缩测试中，它们弹性变形直至第一个位错形核，之后塌陷成薄饼状。在此，我们通过实验和原子模拟表明，镍纳米颗粒与钴合金化会降低其极限强度。这种违反直觉的固溶软化效应是由溶质引起的分解切应力的局部空间变化所解释的，导致位错过早形核。随后颗粒变形需要更多功，使其更坚韧。强度与韧性之间新出现的权衡使合金纳米颗粒成为有前景的应用候选材料。
