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Possibilities of Bulk Nanostructured Metals as Advanced Structural Material

2015-08-18

Seminar by Professor N. Tsuji from Kyoto University

You are cordially invited to attend a seminar by Professor Tsuji from Kyoto University.

Time: Friday September 11 at 11:00am.

Place: Room IP2 at the Division of Industrial Production in the M-Building on the LTH campus.

RSVP to the host, Professor Dmytro Orlov at the Division of Materials Engineering, at: dmytro.orlov@material.lth.se. Then you can also make an appointment if you want to discuss with Professor Tsuji in private.

Abstract

Bulk nanostructured metals (or ultrafine grained (UFG) metallic materials), of which mean grain size of the matrix is smaller than 1 μm, usually perform surprisingly high strength, high fatigue strength and good low-temperature toughness, but their tensile ductility, especially uniform elongation, is limited in many cases. This is attributed tothe early plastic instability caused by their high flow stress and limited strain-hardening capability [1]. Therefore, an important strategy for managing both strength and ductility in nanostructured metals is to increase the strain-hardening capability by controlling microstructures, such as, dispersing nano-particles in the UFG matrix, making the nanostructure multi-phased structures, etc. [2]. Nanostructures fabricated by severe plastic deformation (SPD) naturally have characteristics of deformation structures. This is one of the main microstructural reasons of limited ductility, as strain-hardened metals usually do not show large tensile elongation. In order to remove the deformed characteristics, annealing processes are often applied to the SPD materials. But in many cases the mean grain size becomes over 1 μm after fully annealed microstructures are obtained in single-phased materials, so that the strength has already decreased very much. Recently, on the other hand, we have succeeded in obtaining fully-annealed nanostructures in some alloys [3,4]. The materials show both high strength and enough strain-hardening ability to result in large uniform elongation. All these ways to manage strength and ductility will be presented in the seminar.

References

[1] N.Tsuji, Y.Ito, Y.Saito and Y.Minamino: Scripta Mater., Vol.45, No.12 (2002), pp.893-899.

[2] N.Tsuji, N.Kamikawa, R.Ueji, N.Takata, H.Koyama and D.Terada: ISIJ International, Vol.48, No.8(2008), pp.1114-1121.

[3] R.Saha, R.Ueji and N.Tsuji: Scripta Mater., Vol.68, Issue 10 (2013), pp.813-816.

[4] Y.Z. Tian, L.J. Zhao, S. Chen, D. Terada A. Shibata, N. Tsuji: J. Mater. Sci., Vol.49 (2014), pp.6629-6639.

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