Zheng Xiangui, Hu Jian, Li Jiongxian, Shi Yinong
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
School of Materials Science and Engineering, East China Jiaotong University, Nanchang 330013, China.
Nanomaterials (Basel). 2019 Apr 4;9(4):546. doi: 10.3390/nano9040546.
Annealing hardening has recently been found in nanograined (ng) metals and alloys, which is ascribed to the promotion of grain boundary (GB) stability through GB relaxation and solute atom GB segregation. Annealing hardening is of great significance in extremely fine ng metals since it allows the hardness to keep increasing with a decreasing grain size which would otherwise be softened. Consequently, to synthesize extremely fine ng metals with a stable structure is crucial in achieving an ultrahigh hardness in ng metals. In the present work, direct current electrodeposition was employed to synthesize extremely fine ng Ni-Mo and Ni-P alloys with a grain size of down to a few nanometers. It is demonstrated that the grain size of the as-synthesized extremely fine ng Ni-Mo and Ni-P alloys can be as small as about 3 nm with a homogeneous structure and chemical composition. Grain size strongly depends upon the content of solute atoms (Mo and P). Most importantly, appropriate annealing induces significant hardening as high as 11 GPa in both ng Ni-Mo and Ni-P alloys, while the peak hardening temperature achieved in ng Ni-Mo is much higher than that in ng Ni-P. Electrodeposition is efficient in the synthesis of ultrahard bulk metals or coatings.
最近在纳米晶（ng）金属和合金中发现了退火硬化现象，这归因于通过晶界弛豫和溶质原子晶界偏析促进了晶界（GB）稳定性。退火硬化在极细的纳米晶金属中具有重要意义，因为它能使硬度随着晶粒尺寸减小而持续增加，否则晶粒尺寸减小会导致材料软化。因此，合成具有稳定结构的极细纳米晶金属对于实现纳米晶金属的超高硬度至关重要。在本工作中，采用直流电沉积法合成了晶粒尺寸低至几纳米的极细纳米晶Ni-Mo和Ni-P合金。结果表明，所合成的极细纳米晶Ni-Mo和Ni-P合金的晶粒尺寸可小至约3nm，且结构和化学成分均匀。晶粒尺寸强烈依赖于溶质原子（Mo和P）的含量。最重要的是，适当的退火在纳米晶Ni-Mo和Ni-P合金中均能诱导出高达11GPa的显著硬化，而纳米晶Ni-Mo达到的峰值硬化温度远高于纳米晶Ni-P。电沉积在合成超硬块状金属或涂层方面效率很高。
