Physical metallurgy of medium-Mn advanced high-strength steels

ABSTRACT

Steels with medium manganese (Mn) content (3∼12 wt-%) have emerged as a new alloy class and received considerable attention during the last decade. The microstructure and mechanical response of such alloys show significant differences from those of established steel grades, especially pertaining to the microstructural variety that can be tuned and the associated micromechanisms activated during deformation. The interplay and tuning opportunities between composition and the many microstructural features allow to trigger almost all known strengthening and strain-hardening mechanisms, enabling excellent strength-ductility synergy, at relatively lean alloy content. Previous investigations have revealed a high degree of microstructure and deformation complexity in such steels, but the underlying mechanisms are not adequately discussed and acknowledged. This encourages us to critically review and discuss these materials, focusing on the progress in fundamental research, with the aim to obtain better understanding and enable further progress in this field. The review addresses the main phase transformation phenomena in these steels and their mechanical behaviour, covering the whole inelastic deformation regime including yielding, strain hardening, plastic instability and damage. Based on these insights, the relationships between processing, microstructure and mechanical properties are critically assessed and rationalized. Open questions and challenges with respect to both, fundamental studies and industrial production are also identified and discussed to guide future research efforts.

KEYWORDS:

• Medium-Mn steels
• advanced high-strength steels
• microstructure
• mechanical properties
• phase transformation
• damage

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Binhan Sun acknowledges the financial support from the National Natural Science Foundation of China [grant number 52275147]. Hao Chen acknowledges the financial support from National Key R&D program of China (Grant 2022YFE0110800 and 2022YFB3705203) and the National Natural Science Foundation of China (grants 51922054 and U1808208).