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The Effect of Nano-precipitates on Strength in a Micro-alloyed Ferritic Steel

Published online by Cambridge University Press:  10 October 2011

H.A. Askari ,
Y.F. Shen ,
C.M. Wang ,
X. Sun  and
H.M. Zbib
H.A. Askari
Affiliation:
Mechanical and Materials Engineering, Washington State University, Pullman, WA.
Y.F. Shen
Affiliation:
Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110004, P.R. China
C.M. Wang
Affiliation:
Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, USA
X. Sun
Affiliation:
Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, USA
H.M. Zbib
Affiliation:
Mechanical and Materials Engineering, Washington State University, Pullman, WA.
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Abstract

A high strength ferritic steel with finely dispersive precipitates was investigated to reveal the fundamental strengthening mechanisms in this alloy. Using energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM), fine carbides with an average diameter of 10 nm were observed in the ferrite matrix of the 0.08%Ti steel, and some cubic M23C6 precipitates were also observed at the grain boundaries and the interior of grains. The dual precipitate structure of finely dispersive TiC precipitates in the matrix and coarse M23C6 at grain boundaries provides combined matrix and grain boundary strengthening. The resulting yield stress is two or three times higher than that of conventional Ti-bearing high strength hot-rolled sheet steels. The effect of the particle size, particle distribution and intrinsic particle strength have been investigated through dislocation dynamics (DD) simulations and the relationship for resolved shear stress for single crystal under this condition has been presented using simulation data. The results show that the finely dispersive precipitates can strengthen the material by pinning the dislocations up to a certain shear stress and retarding the recovery as well as annihilation of dislocations. The DD results also show that strengthening is not only a function of the density of the nano-scale precipitates but also of their size. This size effect is explained using a mechanistic model developed based on dislocation-particle interaction.

Keywords

steeldislocationsstrength
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1296: Symposium O – New Methods in Steel Design—Steel Ab Initio , 2011 , mrsf10-1296-o05-04
Copyright
Copyright © Materials Research Society 2011

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