Evolution of precipitate coarsening reaction in a nanostructured Fe-Ni-Mn maraging alloy

Syamak Hossein Nedjad 2Mahmoud Nili Ahmadabadi 3Tadashi Furuhara 1Tadashi Maki 1

1. Kyoto University, Kyoto 606-8501, Japan
2. Sahand University of technology (SUT), Sahand New Town, Tabriz, Iran, Tabriz 51335-1996, Iran
3. University of Tehran (UT), North-Kargar, Tehran 14395-731, Iran

Abstract

Fe-Ni-Mn maraging alloys show discontinuous coarsening of f.c.t. θ-NiMn precipitates along prior austenite grain boundaries (PAGBs) during isothermal aging. Heavy cold rolling of a solution annealed Fe-10Ni-7Mn (wt. %) maraging alloy and subsequent aging treatment at 773 K were found to result in the formation of a nanostructured material. Hardness measurement and transmission electron microscopy were used to study the aging behavior and microstructural evolution of the nanostructured alloy. At early stages of aging, an ultrafine grained structure was observed showing fine matrix precipitates. However, at later stages of aging, severe coarsening of precipitates was found. Consequently, a lamellar duplex microstructure composed of conventional precipitation hardened laths and ultrafine grained ferrite was identified in an intermediate aging time. Coarse f.c.t. θ-NiMn precipitates were identified among ultrafine grained ferrite. At longer stages of aging, evolution of the coarsening reaction were found to result in the development of the ultrafine grained ferrite regions.

Keywords: Nanostructure: Cold Rolling: Maraging: Precipitation: Coarsening

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium I, by Mahmoud Nili Ahmadabadi
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-31 13:50
Revised:   2009-06-07 00:44
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