Abstract
Medium Mn steels have emerged as the so-called 3rd generation advanced high strength steels (AHSS) because they potentially have better properties than the low alloyed first generation AHSS (dual phase and TRIP steels) but with lower alloying levels and subsequent issues associated with the 2nd generation TWIP AHSS.  In this work, medium Mn (between 4 and 10% Mn) were designed with Si and Al additions calculated to reach stacking fault energies associated with twinning of the retained austenite.  Although both twinning and tripping was achieved, the steels proved to be very brittle.   It was hypothesized that Si additions could be causing embrittlement problems and, therefore, alloys were made to explore the effect of Si on mechanical properties.  The steels created showed extremely different stress-strain behaviour, with some microstructures exhibiting excellent strength – ductility combinations.  However, the effect of Si is not straightforward, and depends on the microstructure, in particular the amount of retained austenite and the presence of delta ferrite.

Prof. Stephen Yue简介：
Professor Stephen Yue, who was selected as the inaugural holder of the Lorne Trottier Chair in Aerospace Engineering (2009), obtained a B.Sc. and Ph.D. in Metallurgy at Leeds University in England in the mid-seventies. He has been Associate Dean of Faculty of Engineering at McGill University from 2005 to 2007, and Chairman of the Department of Mining and Materials Engineering from 2007 to 2015. He is currently director of the McGill Institute for Aerospace Engineering. He teaches a variety of courses in materials science and engineering, including ‘Structure of Materials’ and 'Phase Transformations'.  
His research interests revolve around the use of high temperature deformation processing to control the final microstructure and mechanical properties of titanium alloys, superalloys, steels, metal-matrix composites, biomaterials and magnesium alloys. He has published over 200 technical papers in journals and refereed conference proceedings, and holds four patents. In 2005, he was selected as ASM International Fellow for his “sustained and outstanding scientific contributions to metal processing research”.