Achieving excellent strength and ductility synergy by δ phase strengthening in low-density high-manganese steel

ABSTRACT

In this study, we developed a novel lightweight Fe-Mn-Al dual-phase with high strength, excellent ductility, and considerable toughness. The study involved a thorough exploration of heat treatment processes and mechanical behaviour. The microstructure of the Fe-Mn-Al dual-phase steel consists of austenite and δ-ferrite. In the early stages of plastic deformation, austenite undergoes primary deformation, leading to a faster increase in dislocation density and microhardness. In later stages, strain is transferred from austenite to δ-ferrite through high-density dislocation walls, resulting in coordinated deformation of the two-phase structure. The excellent strength-ductility combination of Fe-Mn-Al dual-phase steel is attributed to multiple stages of continuous work hardening. Initially, dislocation nodes in δ-ferrite contribute to work hardening. Subsequently, high-density dislocation structures and the strengthening effect of hard δ-ferrite enhance work hardening. Finally, deformation twins in austenite, along with the TWIP effect, further increase work hardening, emphasizing the importance of these interactions in improving mechanical performance.

KEYWORDS:

• High-manganese steel
• low density
• solid solution
• mechanical behaviour
• TWIP effect
• work hardening

Acknowledgments

G. Niu and D.H. Jing appreciate the support from the National Natural Science Foundation of China (Grant Nos. 52304389, 51774033 and 51474031). G. Niu appreciates the support from the China Postdoctoral Science Foundation (2022M720402). N. Gong appreciates the support from the Structural Metal Alloy Program (SMAP), Grant No. A18B1b0061, and Manufacturing of Multi-Material Net-Shape Parts with Heterogeneous Properties (MMNH), Grant No. M22K5a0045 in A*STAR. N. Gong thanks Professor R.D.K. Misra for a valuable review of the study and corrections.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

The work was supported by the China Postdoctoral Science Foundation [2022M720402]; National Natural Science Foundation of China [52304389, 51774033 and 51474031].