Quantitative Study of Strain-Enhanced Atomic Transport in Mechanically Milled Metal Powders

对金属粉末在球磨过程中组织和显微组织参数的时间演变进行了定量研究。采用球磨机设计，以温度和磨球强度为主要控制变量，对粉体温度、磨球强度和气氛进行精确的了解和控制。感兴趣的材料参数包括晶粒尺寸、均方根弹性应变、长程和短程有序参数、过饱和溶液中的溶解度、两相混合物中的畴尺寸以及非晶合金中的结晶分数。材料的表征是通过x射线衍射，差示扫描量热法，扫描和透射电子显微镜。对实验结果的详细分析应提供塑性变形和热恢复对各参数演化的贡献表达式。结果与辐射增强扩散理论和辐射诱导相形成理论相似。最重要的是，期望从热恢复项中获得塑性变形增强扩散的定量证据。这项工作有望为球磨过程中发生的微观过程提供新的定量理解。预计在系统微结构设计方面获得的经验将有助于未来的实际应用。* * *

9500617 Atzmon A quantitative study is made of the temporal evolution of structural and microstructural parameters of metal powders during ball milling. A ball mill design is employed which allows precise knowledge and control of the powder temperature, milling intensity and atmosphere with the temperature and milling intensity as main control variables. Materials parameters of interest include grain size, root-mean-square elastic strain, long- and short-range order parameters, solubilities in supersaturated solutions, domain sizes in two-phase mixtures, and the crystallized fraction in amorphous alloys. Characterization of the material is by x-ray diffraction, differential scanning calorimetry, and scanning and transmission electron microscopy. Elaborate analysis of experimental results should provide expressions for the contributions of plastic deformation and thermal recovery to the evolution of each parameter. The results are interpreted in analogy with theories of radiation-enhanced diffusion and radiation-induced phase formation. Most importantly, quantitative evidence for plastic deformation enhanced diffusion is expected to be obtained from the thermal recovery term. %%% This work is expected to provide new and quantitative understanding of microscopic processes occurring during ball milling. It is anticipated that the experience gained in systematic microstructural design will help in prospective practical applications. ***