J. Mater. Sci. Technol. ›› 2018, Vol. 34 ›› Issue (3): 417-420.DOI: 10.1016/j.jmst.2017.11.045

Special Issue: High Strength Alloys-2018

• Orginal Article •     Next Articles

Alloy design by dislocation engineering

M.X. Huang*(), B.B. He   

  1. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
  • Received:2017-11-17 Revised:2017-11-18 Accepted:2017-11-18 Online:2018-03-20 Published:2018-03-20
  • Contact: Huang M.X.
  • About author:

    Dr. Huang is currently an Associate Professor at Depart-ment of Mechanical Engineering, University of Hong Kong. He received his BEng and MSc in Solid Mechanics from Shanghai Jiao Tong University (SJTU) in 2002 and 2004, respectively, and his PhD in Materials Science from Delft University of Technology (TU Delft) in 2008. Dr. Huang was a Research Engineer at ArcelorMittal in Maizieres-les- Metz, France, from 2008 to 2010. In 2010, Dr. Huang joined University of Hong Kong as an Assistant Professor and was promoted to Associate Professor with tenure in 2016. He is an editorial board member of Materials Science and Tech-nology and Metallurgical and Materials Transactions A. Dr. Huang received twice the Outstanding Reviewer Award from Scripta Materialia. Dr. Huang’s works have been published in top journals of his research field including Science, Acta Materialia, Journal of Mechanics and Physics of Solids and International Journal of Plasticity. His current research inter-ests focus on two areas: (1) fundamentals of microstructure-property relationship and phase transformation of metals and alloys, and (2) development of lightweight high-strength steels for automotive applications. Both experimental and modelling works are involved in his research. Dr. Huang’s research projects include funda-mental projects as well as industry-oriented projects and have been well funded by General Research Fund, Innovation and Technology Fund, National Science Foun-dation of China, and industries from Europe and China (e.g. ArcelorMittal France, General Motors, Ansteel).

Abstract:

Ultra-high strength alloys with good ductility are ideal materials for lightweight structural application in various industries. However, improving the strength of alloys frequently results in a reduction in ductility, which is known as the strength-ductility trade-off in metallic materials. Current alloy design strategies for improving the ductility of ultra-high strength alloys mainly focus on the selection of alloy composition (atomic length scale) or manipulating ultra-fine and nano-grained microstructure (grain length scale). The intermediate length scale between atomic and grain scales is the dislocation length scale. A new alloy design concept based on such dislocation length scale, namely dislocation engineering, is illustrated in the present work. This dislocation engineering concept has been successfully substantiated by the design and fabrication of a deformed and partitioned (D&P) steel with a yield strength of 2.2 GPa and an uniform elongation of 16%. In this D&P steel, high dislocation density can not only increase strength but also improve ductility. High dislocation density is mainly responsible for the improved yield strength through dislocation forest hardening, whilst the improved ductility is achieved by the glide of intensive mobile dislocations and well-controlled transformation-induced plasticity (TRIP) effect, both of which are governed by the high dislocation density resulting from warm rolling and martensitic transformation during cold rolling. In addition, the present work proposes for the first time to apply such dislocation engineering concept to the quenching and partitioning (Q&P) steel by incorporating a warm rolling process prior to the quenching step, with an aim to improve simultaneously the strength and ductility of the Q&P steel. It is believed that dislocation engineering provides a new promising alloy design strategy for producing novel strong and ductile alloys.

Key words: Alloy design, Dislocation engineering, D&P steel, Q&P steel, TRIP, Warm rolling