Medium-manganese steels processed by austenite-reverted-transformation annealing for automotive applications

ABSTRACT

In the automotive industry, the current development trend of lightweight and low-emission vehicles requests for high-performance materials. Benefiting from an excellent balance of mechanical properties and production cost, medium-Mn steels have attracted extensive interest by materials scientists. Austenite-reverted-transformation annealing plays a vital role in stabilisation of retained austenite and grain refinement, resulting in a considerable amount of retained austenite. Localised deformation phenomenon is usually observed in the ultrafine-grained medium-Mn steels owing to the absence of strain hardening. The occurrence of transformation-induced-plasticity and/or twinning-induced-plasticity effect in austenite improves strain hardening effectively. In the current review, austenite-reverted-transformation annealing treatment routine, mechanical properties and deformation mechanisms and effect of heat treatment on microstructure and mechanical properties of medium-Mn steels are summarised.

This review was submitted as part of the 2017 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged

KEYWORDS:

• Medium-Mn steels
• austenite reverted transformation
• transformation-induced plasticity
• twinning-induced plasticity
• austenite stability
• mechanical properties

Acknowledgements

The author gratefully acknowledges Professor Wolfgang Bleck, Dr Wenwen Song and Dr Xiaofei Guo for fruitful discussion. Some figures are reproduced with kind permission from Wiley-VCH Verlag GmbH & Co. KGaA (Figure 1), Elsevier (Figures 3, 8, 10, 11) and Springer (Figure 4, 6, 7, 9, 13, 14, 15).

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Centre (SFB) 761 ‘Steel – ab initio’.