Gradient structured (GS) materials are ubiquitous in biological systems and now increasingly adopted in engineering systems to achieve desirable combinations of mechanical properties. However, how to control and characterize the gradient structure still remains challenging. In the present work, pure Ni samples possessing a gradient structure with a change in the grain size up to three orders of magnitude from 29 nm to 4 μm are prepared by electrodeposition, where the degree of grain size gradient is accurately controlled. The GS Ni samples exhibit a favorable combination of high strength and high ductility. An optimal grain size distribution profile is discovered which gives rise to a yield strength of 460 MPa and a uniform elongation of 8.9%, the latter even better than that of the coarse-grained Ni. Experimental observations and molecular dynamics simulations reveal that the surface roughening of coarse grains and strain localization of nano-grains can be effectively suppressed by the mutual constraint between nano-grains and coarse grains, leading to the observed superior uniform elongation. This work not only reports a promising methodology of producing materials possessing both high strength and high ductility, but also provides a model for investigating the deformation mechanism in GS materials.

梯度结构（GS）材料在生物系统中无处不在，现在越来越多地在工程系统中采用，以实现理想的机械性能组合。然而，如何控制和表征梯度结构仍然具有挑战性。在目前的工作中，通过电沉积制备具有梯度结构的纯Ni样品，该梯度结构具有从29 nm到4μm的三个尺寸变化的晶粒尺寸，可以精确地控制晶粒尺寸梯度的程度。GS Ni样品表现出高强度和高延展性的良好组合。发现了最佳的晶粒尺寸分布轮廓，其产生了460 MPa的屈服强度和8.9％的均匀伸长率，后者甚至比粗粒Ni还要好。实验观察和分子动力学模拟表明，纳米晶粒与粗晶粒之间的相互约束可以有效地抑制粗晶粒的表面粗糙化和纳米晶粒的应变局部化，从而观察到优异的均匀伸长率。这项工作不仅报告了一种有前途的生产具有高强度和高延展性的材料的方法，而且为研究GS材料的变形机理提供了模型。