Avaliação da transformação martensítica induzida por deformação, e sua transformação reversa e sua influência nas propriedades mecânicas do aço inoxidável duplex 2304

Abstract

Duplex stainless steel combines the mechanical properties of ferrite with the corrosion resistance of austenite and is widely used in industrial applications that require a good performance in these properties. When the duplex steel is subjected to intense deformation the austenite is partially transformed into martensite, increasing the mechanical strength of the steel. Already when the annealing is done, this transformation is reversed, that is, the martensite becomes austenite, causing a grain refining of the material. The objective of this work is to evaluate the martensitic transformation induced by the deformation and its reverse transformation in duplex stainless steel 2304 as well as its effect on the mechanical properties of the selected steel. The steel was subjected to cold rolling, with two deformation routes, 4% to 22% and 60%. Samples with 60% reduction were annealed in the range of 600 °C to 900 °C for 1800 s. For the microstructural analysis, transmission electron microscopy, X-ray diffraction and backscatter diffraction were used. For the mechanical characterization, the tensile test was performed. The diffraction technique by backscattered electrons was also used to evaluate the texture evolution. For deformations up to 22% the presence of and 'martensite was noted, for 60% reduction only ' can be observed. The Shoji-Nishiyama orientation ratio // was found. The orientation relationships between -martensite and austenite were Kurdjumov-Sachs (111) // (110) [110] // [111] and NishiyamaWassermann (111) // (110) [110] // [001] . The martensite contributed to the increase of the yield stress and reduction of the total elongation. The reverse martensitic transformation presented characteristics of shear and diffusion reversion.