Effect of Cold Rolling on the Microstructural Evolution and Mechanical Properties of Austenitic Stainless Steel Containing Niobium

Austenitic stainless steel has excellent ductility. Consequently, it has capability for heavily cold deformation, despite its high strength and high work hardening ability. Austenitic stainless steel predominantly contains high levels of chromium and nickel. Additional elements may be added to enhance performance. The target of this paper is to study several austenitic stainless steel alloys containing different Nb pct. The main merit of Nb is to avoid the sensitization phenomenon during during cooling from high temperatures or heating service. Another target of study is to demonstrate the effects of the chemical composition on strength as well as the effect of cold rolling on the creation of induce martensite phase is also studied. The microstructural investigation shows that grain coarsening was observed on the as-cast structure accompanying with thick grain boundary carbides along with carbide agglomerations at the triple points. Hot deformation diminishes the grains as well as the carbide films surrounding the grains. Solution treatment creates austenitic grains free of grain boundary carbides. Cold deformation creates highly elongated grains associated with wavy pancaked structure. Nb was found to increase the proof strength even at high temperatures. The measured mechanical properties of the alloys under investigation are higher values due to the Nb effect. The flow curve of different alloys has been extensively studied. The detected results have been verified by the microstructural changes during deformation.