Effects of Hot Rolling on the Microstructure, Mechanical, and Damping Properties of High‐Nitrogen Stainless Steel

Abstract

In this study, the mechanical and damping properties of high‐nitrogen stainless steel, containing 0.65 wt% nitrogen, after being subjected to hot rolling to deformation ratios 19%–85% are investigated. Mechanical properties are assessed using tensile testing and Vickers hardness testing while damping properties are analyzed using a dynamic mechanical analyzer. A significant improvement in tensile strength is observed in samples deformed to an 85% reduction, showing an ultimate tensile strength of 1227 MPa compared to the initial 810 MPa of the annealed sample. Both the frequency and temperature damping capacities increase with the amount of deformation, peaking at 66% reduction, before slightly declining at 85% reduction. In the study, Finkelshtain–Rosin internal friction peaks, characteristic of austenitic steels, are identified in the temperature range of 100–250 °C. Deformation up to a 66% thickness reduction results in deformed grains with a continuous increase in dislocation density, accounting for trends in the mechanical and damping properties. However, the 85% reduction leads to a finer microstructure with a high fraction of low‐angle grain boundaries formed through continuous dynamic recrystallization during hot rolling. This creates immobile dislocation networks, which adversely affect the damping properties.