Per: Nayara Aparecida Lopes Viana (Departamento de engenharia metalúrgica e de materiais da ufmg), Loren Kelly de Paula Inácio (DEPARTAMENTO DE ENGENHARIA METALÚRGICA E DE MATERIAIS DA UFMG), Renata de Oliveira Melo (DEPARTAMENTO DE ENGENHARIA METALÚRGICA E DE MATERIAIS DA UFMG), Graziele Gianini Braga Maria (DEPARTAMENTO DE ENGENHARIA METALÚRGICA E DE MATERIAIS DA UFMG), Witor Wolf (DEPARTAMENTO DE ENGENHARIA METALÚRGICA E DE MATERIAIS DA UFMG), Dagoberto Brandão Santos (DEPARTAMENTO DE ENGENHARIA METALÚRGICA E DE MATERIAIS DA UFMG)
Abstract:
Duplex stainless steels combine the mechanical properties of ferrite with the corrosion resistance of austenite. When this material is subjected to heat treatments, secondary phases may precipitate, resulting in severe deterioration of corrosion and mechanical properties. The goal of this work was to evaluate the occurrence of secondary phases in a cold rolled 2205 duplex stainless steel with an ultrafine grain after aging at temperatures ranging from 600°C to 950°C for different times (300-86400 s). Scanning electron microscopy (SEM) coupled with electron backscattered diffraction (EBSD) and x-ray diffraction (XRD) were used for phase identification and quantification. Mechanical properties were evaluated using tensile and Vickers microhardness tests. The presence of and phases was observed together chromium carbide, M23C6, and were confirmed only after 800ºC ageing treatment. In a general way, an increase in the aging time led to a greater precipitation of the secondary phases. As precipitation occurred, there was an increase in the austenite and a decrease in the ferrite volume fractions. Although mechanical strength has increased, the overall mechanical properties, such as ductility, were impoverished as the precipitation proceeded.
