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Determination of dislocation density and crystallite size distribution in deformed lath martensite by X-ray peak profile analysis

Mohamad reza Movaghar Garabagh 1Syamak Hossein Nedjad 1Hassan Shirazi 2Mohsen Iranpour Mobarekeh 2Mahmoud Nili Ahmadabadi 2

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

Abstract

Microstructrual characteristics of extra low carbon lath martensite after equal channel angular pressing of four passes and cold rolling to 85% reduction were studied by means of X-ray peak profile analysis and transmission electron microscopy. The modified Williamson-Hall and Warren-Averbach methodologies were implemented to determine crystallite size distribution, dislocation density and character of prevailing dislocations of the deformed structures. It was found out that lath boundaries disappear at large strain which successively turn to a highly and uniformly dislocated structure. Cold-rolled steel showed lamellar dislocation cell blocks in which strong preferred orientation could be deduced from anisotropy of integral width according to the classic Williamson-Hall approach. However, equiaxed dislocation cells of random orientation were found in the equal channel angular pressed steel. It is demonstrated that further straining would be necessary to realize a bulk nanostructured steel with high fraction of high angle boundaries.

 

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Related papers

Presentation: Poster at E-MRS Fall Meeting 2007, Symposium H, by Hassan Shirazi
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-08-10 22:53
Revised:   2009-06-07 00:44