C clustering and partitioning by static strain aging in cold-rolled 16Cr-5Ni supermartensitic stainless steel

Static strain aging behavior of cold-rolled 16Cr-5Ni supermartensitic stainless steel was investigated after it had been aged for 30 min at 400 degrees C. In uniaxial tensile tests of 20% cold-rolled specimens, increase of yield strength to similar to 300 MPa and decrease of strain hardening rate were observed in the aged specimen, compared to the as-rolled specimen. In interrupted tensile tests, delayed martensitic transformation was observed in the aged specimen. Dilatometry analysis detected volume shrinkage during the 30 min holding period at 400 degrees C indicating partitioning of carbon (C) from alpha' martensite to austenite. The clustering of C in alpha' martensite was confirmed by impulse internal friction technique with observation of Cottrell atmosphere formation. 3D atom probe tomography analysis revealed partitioning of C atoms into austenite and clustering of C atoms in the alpha' martensite. The remarkable increase of yield strength was attributed to redistribution of C atoms during the aging treatment. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study revealed that after aging at 400 degrees C for 30 minutes, cold-rolled 16Cr-5Ni supermartensitic stainless steel showed a significant increase in yield strength, a decrease in strain hardening rate, delayed martensitic transformation, and redistribution of carbon atoms.