应变诱导Ni原子在纳米晶Fe中的扩散行为研究（英文）

Strain-Induced Diffusion of Nickel in Nanocrystalline Fe Produced by High Energy Shot Peening

利用高能喷丸法(HESP)在工业纯铁表面制备了一定厚度无污染、空位、杂质等缺陷的纳米晶层,其平均晶粒尺寸为50 nm,厚度为100μm。在Gleeble 1500热模拟机上,采用脉冲加压扩散(PPD)和恒定加压扩散(CPD)对纳米晶铁在850℃下进行渗镍处理。结果表明,镍原子在纳米晶铁中的扩散系数比常规粗晶中高1个数量级;而采用脉冲加压扩散时,镍原子的扩散系数要比采用恒压扩散高1个数量级。镍原子扩散系数的提高主要包括三方面的原因,一是脉冲加压能击碎扩撒界面上形成的阻碍镍原子扩散的金属件化合物;二是纳米晶铁中形成的大量三叉晶界;三是纳米晶铁中形成大量的非平衡晶界。

A nanocrystalline surface layer without oxidation, porosity or contamination was obtained by high energy shot peening（HESP） to a pure iron cylinder. The thickness of the nanocrystalline surface layer was more than 100 μm and the average grain size was about 50 nm. The pulse pressure diffusion（PPD） and constant pressure diffusion（CPD） were used to diffuse nickel into nanocrystalline iron at 850 °C on Gleeble 1500. Results show that the diffusion coefficient of Ni in the nanocrystalline Fe is 1 order of magnitude higher than that in coarse-grained Fe and 1 order of magnitude higher than that using CPD. The enhanced diffusivity of Ni may originate from the following three reasons：（1） pulse pressure can break the metallic compound formed during diffusing which may block the diffusion of Ni to inner nanocrystalline Fe;（2） a considerable amount of triple junctions and（3） a large volume fraction of non-equilibrium grain boundaries（GBs） in the present nanocrystalline Fe sample processed by the HESP technique.