Deformation mechanisms of TWIP steel: from micro-pillars to bulk samples
Twinning-induced plasticity (TWIP) steels have excellent combination of strength and ductility and are potential lightweight materials for automotive applications. Understanding the deformation mechanisms in TWIP steels is essential for the successful application of TWIP steels. The first part of this work is to employ micron-sized single crystalline pillars to investigate the nucleation and growth mechanism of deformation twins. It is found that the nucleation and growth of deformation twins are due to emission and glide of successive partial dislocations. A physical model is proposed to simulate the nucleation and growth of deformation twins. The second part of the presentation discusses the deformation mechanism of bulk samples. Deformation mechanism of bulk samples at high strain rates will be discussed firstly. By synchrotron X-ray diffraction experiments, the present work demonstrates that a higher strain rate leads to a lower dislocation density and a lower twinning probability, which is opposite to other fcc metals. Furthermore, it has been demonstrated that the contribution of twins to the flow stress is very limited. Instead, dislocations strengthening via forest hardening accounts for up to 90% of the flow stress. In other words, the contribution of twins to flow stress of TWIP steels may have been overestimated in the existing literature. Finally, the present talk will discuss a nanotwinned steel which is manufactured by a simple thermomechanical treatment consisting of cold rolling and recovery annealing and possesses a high yield strength (1450 MPa) and considerable uniform tensile elongation (20%).
Dr. Mingxin Huang
Associate Professor
Department of Mechanical Engineering
The University of Hong Kong
Pokfulam
Rm 717, Haking Wong Building
Hong Kong
| Phone | +852 2859 7906 |
| Dr. Mingxin Huang | |
| Http | Dptm. of Mech. Eng. |
Short biography
Dr. Mingxin HUANG is currently an Associate Professor at The University of Hong Kong, Hong Kong. His research interests focus on two areas: (1) fundamentals of microstructure-property relationship and phase transformation of advanced steels, and (2) development of lightweight materials for automotive applications. Both experimental and modelling works are involved in his research. His research projects have been well funded by government funding agents as well as industries from Europe and China (e.g. ArcelorMittal France, General Motors, Ansteel, Baosteel).
Dr. Huang received his Bachelor as well as Master degrees from Shanghai Jiao Tong University (SJTU) in 2002 and 2004, respectively, and his PhD in 2008 from Delft University of Technology (TU Delft), The Netherlands. From 2008 to 2010, he worked as a research engineer at ArcelorMittal R&D centre in Maizieres-les-Metz, France. His research work in ArcelorMittal focused on the development of new advanced steels for automotive applications. Dr. Huang joined University of Hong Kong in 2010 as an Assistant Professor and was promoted to Associate Professor with tenure in 2016. Dr. Huang has published 50+ journal papers on major international journals in his field such as Acta Materialia and Scripta Materialia. Dr. Huang is an editorial board member of Materials Science and Technology, the Key Reader for Metallurgical and Materials Transactions A and has received twice “Outstanding Reviewer of Scripta Materialia” awards.