Influence of strain rate on hot ductility of austenitic stainless steel slab

Abstract

The effect of strain rate on the deformation behaviour of Cr15Mn9Cu2NiN slab has been studied through hot tensile tests on Thermorestor-W. Results showed that, as the strain rate increases from 0·1 to 10 s⁻¹ at a given test temperature, the reduction in area (RA) in slab shell decreases by 20%, and the positions of crack nucleus were changed from δ ferrite dendrites to austenite grain boundary, while in slab core, RA only decreased by 5% and the crack nucleus was on austenite grain boundary all the time. There are many ferrite/austenite interfaces in the microstructure of shell. As the materials deform at higher strain rate, dislocations will be generated and piled up at the interface quickly, and improve the strength in both austenite and ferrite, which will result in the stress concentration at austenite grain boundary and lead to crack nucleation.

Keywords:

• Austenitic stainless steel
• Strain rate
• δ ferrite dendrite
• Columnar grain
• Crack nucleating position

Financial support from the National Natural Science Foundation of China (grant no. 51264026).