1. Department of Microstructure Physics and Metal Forming Düsseldorf, Germany C. Herrera, D. Ponge, D. Raabe Microstructure and deformation mechanisms of a Mn ‐ based lean 1 GPa duplex stainless TRIP steel with high ductility

2. MPIE Experimental procedure Chemical composition (mass%) Alloys CrNiMnNCCuSiMo Alloys20 - 25≤ 1≤ 50.05-0.3≤ 0.13≤ 2≤ 0.5- 1.4362 22.323.651.390.108 0.024-0.220.41 Alloy MnNC Low Mn ~3.0~ 0.20 High C, middle N and Mn ~ 5.0~ 0.25~ 0.20 Low C, high N, middle Mn ~ 5.0~ 0.35~ 0.03 Low C and N, high Mn ~ 8.0~ 0.10 Hot rolling + Cold rolling + Annealing treatment, T Annealing = 1050°C/5min

3. MPIE Alloy , %* M d (  ), °C YS, N/mm² UTS, N/mm² Uniform elongation, % Total elongation, % Low Mn508144576119 High C, middle N and Mn64 50310265558 Low C, high N, middle Mn60374757003153 Low C and N, high Mn 97473267587973 1.436257284326975155 Result – Mechanical properties Hot rolling + Cold rolling + Annealing treatment, T Annealing = 1050°C/5min * Volume fraction of  before tensile test

4. MPIE Austenite Results – Microstructure Ferrite Low Mn  %  before = 50 %  after = 3.3 (Md)  = 81°C 0° 2° ND RD

5. MPIE Results – Alloy with high C and middle N and Mn Evolution of the microstructure during tensile test   = 0.10   = 0.15 Volume fraction of  before and after tensile test: %  before = 64 %  after = 14 (Md)  = 64°C   = 0.20   = 0.46 ND RD

6. MPIE  = 0.46 bcc phases Austenite  -martensite Results – Alloy with Middle N and Mn

7. MPIE The high strength level and the excellent forming properties qualify lean duplex stainless TRIP steels for advanced lightweight and high- strength manufacturing applications in the fields of mobility, industrial design, and energy conversion under less corrosive conditions. Conclusion

8. MPIE Application of lean duplex stainless steels Rotating Shelter - Blackpool (England) The Helix Bridge (2010) - Singapore Stonecutters Bridge (2009) - Hong Kong Attractive combinations of good mechanical properties and high corrosion resistance Weight reduction Offshore Brazil