Martensitic transformation and fractographic analysis of lean duplex stainless steel during low temperature tension deformation

Martensitic transformation and matching fracture behaviors in lean duplex stainless steel 2101 (LDSS) during tension deformation at low temperature were investigated. The low-temperature tensile tests were conducted using tensile speed of 0.5 mm/min at − 30 °C, − 50 °C and − 70 °C. The results indicated that the stress-strain curves of lean duplex stainless steel 2101 at low temperatures show a work hardening and softening mode at different temperatures. The morphology of the strain-induced martensite is lath-like at − 30 °C, bow-like at − 50 °C and fold-like at − 70 °C. The ε-martensite is not observed in the lean duplex stainless steel and the slip planes are high-index crystalline faces. The martensitic transformation mechanism is γ (fcc) → α′(bcc) during the deformation of lean duplex stainless steel. Moreover, the strain-induced martensite improves the tension resistance by either hindering the crack propagation or reducing the crack growth rate. The fractography of matching fracture surfaces shows a mixture of dimple fracture in ferritic phase and austenitic phase.