J. Phys. IV France
Volume 112, October 2003
Page(s) 381 - 384

J. Phys. IV France
112 (2003) 381
DOI: 10.1051/jp4:2003906

Effect of stacking fault energy and austenite strengthening on martensitic transformation in Fe-Mn-Si alloys

J. Wan, S. Chen and T.Y. Hsu (Xu Zuyao)

School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030, China

In the Fe-Mn-Si alloys with very low stacking fault energy ( $\gamma_0$), the $\gamma$(fcc) $\to$(hcp) martensitic transformation substantially relies on an overlapping-of-stacking-faults mechanism. $\gamma_0$ strongly influences its Ms temperature. Ms gets lowered when $\gamma_0$ increases. It has been shown that both Mn and Si strengthen the austenitic matrix. However, Mn in a certain concentration range raises $\gamma_0$ of the alloy and thus lowers its Ms while Si acts in the other way around. Carefully summarizing and treating the available theoretical and experimental data, an analytical expression is established to describe the Ms as a function of $\gamma_0$ and the strengthening effect that is related with the strain energy. The results show that stacking fault energy plays an overwhelming role on the transformation in such alloys, even though the austenite strengthening also lowers Ms to some extent.

© EDP Sciences 2003