Abstract
Prestrained at 5% and 15% duplex stainless steel UNS S32750 specimens have been subjected to electropulsing treatments with current density of 100 A/mm2 and 200 A/mm2 and 100 and 500 pulses for each current density value. Corrosion tests, X-ray diffraction, microhardness and residual stresses were collected before and after the electropulsing treatments. Tensile tests were performed after the electropulsing treatments in order to compare the mechanical response to reference tensile tests performed before pulsing treatments. Increase in fracture strain was observed after pulsing treatment in comparison to the reference tensile tests. A decrease in microhardness was also observed after electropulsing treatments for both degrees of prestrain. Electropulsing treatment almost eliminates the work-hardened state in the 5% prestrained specimens while partially recovered the 15% prestrained material increasing both uniform and fracture strain. Bulk temperature of the samples remained the same for all treatments duration. The effect are to be addressed to a combined effect of increase in atomic flux due to the electrical current and local joule heating in correspondence of crystal defects. Electropulsing treatment applied to metallic alloys is a promising technique to reduce the work hardening state without the need of annealing treatments in a dedicated furnace.
Highlights
Duplex stainless steels (DSSs) are a peculiar category of stainless steels characterized by their biphasic microstructure consisting of almost equal volume fraction of austenite and ferrite
It absorbs much of the early stage deformation because it possesses 12 lowshear strength preferred slip systems and allows easy dislocation mobility in almost all crystallographic directions while ferrite is characterized by relatively higher-shear strength slip systems, which typically possess higher critically resolved shear stresses for their activation [54]
Even though ferrite has more slip system, its Peierls stress is higher compared to the yield stress of austenite, justifying the fact that austenite is more ductile than ferrite
Summary
Duplex stainless steels (DSSs) are a peculiar category of stainless steels characterized by their biphasic microstructure consisting of almost equal volume fraction of austenite and ferrite They are employed in different applications, such as oil and gas, paper and pulp industry, the wine industry, etc. A balanced microstructure consisting of equal amounts of austenite and ferrite is necessary in order to obtain the best combination of mechanical and corrosion properties. This can be achieved with a suitable composition and a solution treatment performed at a temperature that depends on the steel composition ( higher than 1050 ◦ C).
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