Ultra-fine grain

In 1986, Wakai et al. (1986) in Japan discovered that ultra-fine-grained ceramics can also be superplastically deformed they may be brittle with respect to dislocation... 

Hillard, J. E., Cohen, J. B., and Paulson, W. M. (1970), Optimum Procedures for determining ultra fine grain sizes, in Burke, J. J., Reed, N. L., and Weiss, V., Eds., Ultrafine Grain Ceramics, Syracuse University Press, Syracuse, New York, pp. 73. 

Taking this circumstance into account some above topics will be analyzed lower in more details. Namely, these are limiting hardening created as a result of obtaining ultra-fine grains, some topics of deformation hardening additionally, considered will be some aspects of development of new generation of titanium-based materials (systems Ti-B-X and Ti-Si-X, where X is Al, Zr, etc.). 

Key words chromium, molybdenum, coatings, ultra-fine grain structure, nanohardness. 

It is shown, that chromium and molybdenum coatings have ultra-fine grain structure (Fig. 1). So, the grains size in 80 and 400 nm thickness chromium and molybdenum coatings are equal to 40 -50 nm and 20 nm accordingly. The diffraction pattern shows that only lines corresponding to lines body-centered cubic lattices chromium and molybdenum are precisely fixed, additional lines are not revealed. 

The nanohardness of 400 nm thickness chromium coatings with ultra-fine grain (nanocrystalline) structure is equal to 21.61 GPa (Table 1), which is 8-9 times higher than that of cast chromium. At the same time the nanohardness of molybdenum coatings, which characterized even more fine-grain structure, is equivalent to 9.98 GPa. It is necessary to note, that in a massive state hardness of polycrystalline chromium is lower than hardness of polycrystalline molybdenum (2 GPa and 1.3 GPa for poly crystalline molybdenum and chromium accordingly [7]). 

S. Hirano, K. Okamoto, K. Aota, and M. Inagaki, Metallurgical and Mechanical Properties of Friction Stir Welded Ultra Fine Grained Steel, Proceedings of the Fifth International Conference on Friction Stir Welding, Sept 14—16, 2004 (Metz, France), TWl, paper on CD... 

DUC] Tensile test Strength and ductility of ultra fine grain sized V (FeCo)3 with temperature. 

Che] Chezan, A.R., Craus, C.B., Chechenin, N.G., Vystavel, T., Niesen, L., De Hosson, J.T.M., Boerma, D.O., On the Formation of Ultra-Fine Grained Fe-Base Alloys via Phase Transformations , Mater. Sci. Eng. A, 367(1-2), 176-184 (2004) (Crys. Stracture, Experimental, Kinetics, Morphology, Phase Relations, 13)... 

W. J. Deng, W. Xia, C. Li, Y. Tang, Formation of Ultra-Fine Grained Materials by Machining and the Characteristics of the Deformation Fields. Journal of Materials Processing Technology 2009,209,4521-4526. 

Iwahashi Y, Wang J, Horita Z, Nemoto M, Langdon TG. Principle of equal-channel angular pressing for the processing of ultra-fine grained materials. Scr Mater... 

Synthesis and Sintering of Fine and Ultra-Fine Grain NZP Ceramics... 

Kim, T Balakrishnan, A Lee, B Kim, W Dvorankova, B Smetana, K Park, J Panigrahi, B. In vitro fibroblast response to ultra fine grained titanium produced by a severe plastic deformation process. Journal of Materials Science Materials in Medicine, 2008, 19, 553-557. 

The maximum of microhardness of steel after EBP exceeds the maximum values of microhardness of steel, hardened after furnace heating and after EEA. Electron-microscopic studies have shown that this is due to the formation of ultra fine-grained (0.54 0.20 pm) stmeture on the surface of processing. The dimensions of martensite crystals in such grains change considerably within the following limits cross - 30...50 nm, longitudinal - 120... 500 nm. 

W.S. Young, S.T. Rasmussen, and I.D. Cutler in Ultra-Fine Grain Ceramics, eds. J.J. Burke, N.L. Reed, and V. Weiss (Syracuse Univ. Press, Syracuse, New York, 1970), pp. 185-202. 

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