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选用直流电沉积制备平均晶粒尺寸为27.2nm,宽晶粒尺寸分布(5~120nm)的纳米镍(简称宽晶纳米镍),在室温采用拉伸应变速率(ε)突变法测量其应变速率敏感指数(m)。发现m随ε的减小而增加,特别在ε小于2×10-5s-1时,m快速增加,m在ε=5×10-6s-1时达到0.054,表明塑性变形过程中晶界扩散、晶界滑移很可能被激活。在室温进行循环加载-卸载拉伸测试,结果表明宽晶纳米镍晶内存储位错的能力十分有限,当拉伸应力达到1052MPa,应变为7.8%时,晶内位错密度达到饱和。通过对拉伸断口附近的TEM观察,证实宽晶纳米镍在塑性变形过程中存在显著的类似粗晶中的晶内位错滑移。
The nanosized nickel with average grain size of 27.2nm and wide grain size distribution (5 ~ 120nm) was prepared by direct current deposition, and its strain rate sensitivity was measured at room temperature by the method of tensile strain rate (ε) Index (m). It was found that m increased with the decrease of ε, especially at ε less than 2 × 10-5s-1, m increased rapidly and m reached 0.054 at ε = 5 × 10-6s-1, indicating that the grain boundary diffusion during plastic deformation , Grain boundary slip is likely to be activated. The cyclic loading-unloading tensile test at room temperature showed that the ability of dislocations to store dislocations in the wide-grain nickel nanocrystals was very limited. When the tensile stress reached 1052 MPa and the strain was 7.8%, the intragranular dislocation density was saturated. The TEM observation of the vicinity of the tensile fracture shows that there is a significant intragranular dislocation slip in the coarse-grained nanocrystalline nickel during the plastic deformation.