Microstructural evolution induced mechanical property enhancement in cryogenically rolled Ce‐modified SAF2507 super duplex stainless steel

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>Thermomechanical deformation is one of the most efficient and facile routes to tailor microstructure in structural materials for mechanical property enhancement. Herein, the Ce‐modified SAF2507 super duplex stainless steel (Ce‐SAF2507) is deformed at different levels from 30% to 90% at a cryogenic temperature (–196 °C) to achieve superior mechanical performances. Cryogenic rolling increase fiber texture and induce ultra‐fine grain refinement which brings grains to ≈10 nm in the selected steel. The high‐density dislocations and deformation twins in the cryogenically rolled Ce‐SAF2507 lead to the nucleation and growth of martensite. Increases in the martensite volume fraction and nanoscale grain refinement occur at higher deformation levels. Cryogenically rolled deformation results in the overall increase in the Ce‐SAF2507 hardness. A higher hardness increment of austenite–martensite dual‐phase compared to that of ferrite is attributed to the austenite–martensite‘s higher work hardening ability. Furthermore, the ultimate tensile strength and yield strength increase with the deformation level, but the elongation decrease. Observed microstructural evolutions induced by cryogenic rolling enunciate the superiority of the present method over conventional ones to promote steel’ mechanical properties.</p></div>