纳米Ni和Ni／SiC_p纳米复合材料的超塑性

Superplasticity of nanocrystalline Ni and Ni/SiC_p nanocomposite

研究了用电沉积方法制备的纳米Ni和Ni／SiCp纳米复合材料的超塑特性,在试验温度410℃ 和450℃,应变速率为8．3×10-4s-1-5×10-2s-1的条件下,纳米Ni和Ni／SiCp纳米复合材料 均表现出超塑性．当温度为450℃、应变速率为1．67×10-2s-1时,在Ni／SiCp中获得最大延伸率为 836％;在同样的温度下应变速率为1．67×10-3s-1时纳米Ni获得最大延伸率为550％．对超塑性变形 后组织的分析表明,晶界滑移是主要变形机制,晶粒长大至亚微米／微米量级后,变形机制是位错协调晶界 滑移和位错滑移塑性．

Superplasticity of nanocrystalline Ni and Ni/SiCp was investigated. Tensile tests were carried out under 410 ℃ and 450 ℃ and strain rates ranging from 8.3×10^-4s^-1 to 5×10^-2s^-1. Low temperature and high strain rate superplasticity was realized in the two materials. A maximum elongation of 836% was obtained in Ni/SiCp nanocomposite under the condition of 450℃ and strain rate of 1.67×10^-2s^-1, and a maximum elongation of 550% for nanocrystalline Ni under the same temperature and strain rate of 1.67×10^-3s^-1. Microstructure of the as-deposited nanocrystalline Ni and Ni/SiCp nanocomposite and deformed samples was observed using SEM and TEM. Analysis of the deformed microstructures showed that grain boundary sliding was the main deformation mechanism. When the grain grew to submicro/micro range, dislocation-mediated grain boundary sliding and dislocation slip plasticity were the deformation mechanisms.