晶界稳定性控制着极细纳米晶粒金属的硬化和软化。

Grain boundary stability governs hardening and softening in extremely fine nanograined metals.

机构信息

Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.

Normandie University, UNIROUEN, Institut National des Sciences Appliquées Rouen, CNRS, Groupe de Physique des Matériaux, 76000 Rouen, France.

出版信息

Science. 2017 Mar 24;355(6331):1292-1296. doi: 10.1126/science.aal5166.

DOI:10.1126/science.aal5166

PMID:28336664

Abstract

Conventional metals become harder with decreasing grain sizes, following the classical Hall-Petch relationship. However, this relationship fails and softening occurs at some grain sizes in the nanometer regime for some alloys. In this study, we discovered that plastic deformation mechanism of extremely fine nanograined metals and their hardness are adjustable through tailoring grain boundary (GB) stability. The electrodeposited nanograined nickel-molybdenum (Ni-Mo) samples become softened for grain sizes below 10 nanometers because of GB-mediated processes. With GB stabilization through relaxation and Mo segregation, ultrahigh hardness is achieved in the nanograined samples with a plastic deformation mechanism dominated by generation of extended partial dislocations. Grain boundary stability provides an alternative dimension, in addition to grain size, for producing novel nanograined metals with extraordinary properties.

摘要

传统金属的晶粒尺寸越小，硬度就越高，遵循经典的霍尔-佩奇关系。然而，在纳米尺度的某些合金中，这种关系会失效，在某些晶粒尺寸下会出现软化现象。在这项研究中，我们发现，通过调整晶界（GB）稳定性，可以改变极其细小纳米晶粒金属的塑性变形机制及其硬度。由于晶界介导的过程，电沉积纳米晶粒镍-钼（Ni-Mo）样品的晶粒尺寸低于 10 纳米时会出现软化现象。通过弛豫和钼偏析稳定晶界，纳米晶粒样品中通过扩展部分位错的产生来实现超高硬度，其塑性变形机制占主导地位。晶界稳定性除了晶粒尺寸之外，为生产具有特殊性能的新型纳米金属提供了另一个维度。