Hossein Seydrezai

PhD Candidate

Department of Mechanical and Materials Engineering

Nicol Hall -Room 303
Queen's University
60 Union Street
Kingston, Ontario, Canada K7L 3N6

Tel: (613) 533-3229

e-mail: rezai@me.queensu.ca

Academic Background

M.A.Sc., Materials Science and Engineering, McMaster University, Hamilton, ON, CANADA (2007)

B.Sc., Metallurgical Engineering, Amirkabir University of Technology, Tehran, IRAN (2005)

Select Publications

Seyedrezai H., Grebennikov D., Mascher P. and Zurob H. S, "Study of the early stages of clustering in Al-Mg-Si alloys using the electrical resistivity measurements", Materials Science and Engineering A., vol.525 (2009) pp.186-191 (doi:10.1016/j.msea.2009.06.054)

Zurob H. S. and Seyedrezai H., "A model for the growth of solute clusters based on vacancy trapping", Scripta Materialia, vol.61 (2009) pp.141-144 (doi:10.1016/j.scriptamat.2009.03.025)

Zurob H. S., Hutchinsonb C. R., Bréchet Y., Seyedrezai H. and Purdy G. R., "Kinetic transitions during non-partitioned ferrite growth in Fe-C-X alloys", Acta Materialia, vol.57 (2009) pp.2781-2792 (doi:10.1016/j.actamat.2009.02.029)

Ketabchi M. and Seyedrezai H., "Energy analysis of L-section extrusion using two different streamlined dies", Journal of Materials Processing Technology, vol.189 (2007) pp.242-246 (doi:10.1016/j.jmatprotec.2007.01.029)

Current Research Description

There is a continuing trend in the automotive industry to move towards lighter, more fuel-efficient vehicles. With improvements in processing technologies, many new materials, mainly aluminum alloys, are emerging as alternatives to plain carbon steel which is widely used in current automobiles. To ensure competitiveness of ferrous alloys, new grades of steel are being produced which have combinations of superior strength, excellent formability and good failure properties. These new steels are often referred to as Advanced High Strength Steels (AHSS). In the present research the focus will be on an AHSS grade called Dual Phase (DP) steels. It is well established that there is a trade-off between higher strength and reduced ductility, which can lead to premature material failure during the manufacturing of components or as a result of in-service loading. In order to overcome this problem, a more fundamental understanding of the microstructural effects on damage properties of these steels is required. This is the motivation behind the proposed research.

Dual phase steels consist of ferrite and non-ferritic phases (NFP). Traditionally the NFP is martensite. More recently, however, the thermo-mechanical process used to produce DP steels has become more complicated by the introduction of other heat treatments before or after inter-critical annealing (referred to as pre-treatments and post-treatments). Therefore the structure of DP steels can now consist of many different phases other than ferrite and martensite, e.g. bainite and retained austenite. It is found that the size, distribution and composition of the NFP can greatly alter the properties of these steels. The first two parameters are functions of the carbon (or carbides) distribution and can be controlled by various pre-treatments. The NFP composition, on the other hand, depends on the post-treatment and is typically controlled by introducing a lower temperature treatment after inter-critical annealing.

In this research, a series of pre-treatments will be introduced to produce significantly different DP microstructures. In addition, mechanical deformation will also be performed at different stages of pre-treatments to further improve the grain refinement.

In the second portion of the project, the relationship between microstructure (produced via various pre-treatments) and mechanical behaviour of DP steels, i.e. strength, work hardening and fracture properties, will be investigated. Quantitative correlations between specific properties and microstructural features will be developed. In addition, an important aspect of this part of the study will be to characterize the development of damage leading to final fracture, by in-situ micro-CT observations and post-fracture sectioning of tensile samples. Finally the effects of strain path on damage and fracture will be determined by other test geometries, such as in-plane plane strain (IPPS) tensile tests.

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