tailieunhanh - Diffusion Solids Fundamentals Diffusion Controlled Solid State Episode 3 Part 5

Tham khảo tài liệu 'diffusion solids fundamentals diffusion controlled solid state episode 3 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Diffusion in Nanocrystalline Metals 607 permanent interest largely because material transport in nanostructured materials belongs to the group of material properties differing most from their coarse-grained or single-crystalline counterparts. An overwiew of the early diffusion measurements on nanocrystalline metals and alloys was given in 40 . More recent developments can be found in a status report of Wurschum AND COWORKERS 28 . In the first diffusion studies in this field diffusivities in nanocrystalline Cu produced by inert-gas condensation and subsequent consolidation were found to be significantly faster than in grain boundaries of conventional polycrystals see . 41 42 . Soon after this initital era it was recognised that factors such as structural relaxation grain growth residual porosity different types of interfaces and perhaps triple junctions must be taken into account to obtain an unambigous assessment of diffusion in nanocrystalline metals. More recent studies taking structural relaxation and grain growth into consideration came to the conclusion that diffusivities in relaxed interfaces of nanocrystalline metals are similar to or only slightly higher than grainboundary diffusivities obtained from conventional bicrystals or polycrystals. Somewhat at variance with the finding that the grain boundary diffusivities of nanocrystalline materials are siminlar to those obtained from conventional polycrystals are the observations of super-plasticity 43 and increased strength and ductility 44 of nanostructured materials processed by severe plastic deformation. These properties have been attributed to the formation of non-equilibrium grain-boundaries with enhanced diffusivity 45 . However so far the existence of such grain-boundary structures has not been established by experiments. Most of the experimental techniques discussed in part II of this book have been applied to diffusion studies on nanocrystalline metals and alloys as well. These methods include

TỪ KHÓA LIÊN QUAN
crossorigin="anonymous">
Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.