Avaliação do impacto da preparação metalográfica na quantificação de austenita retida via EBSD em aço AHSS

Abstract

Advanced High Strength Steels (AHSS) have been implemented in greater quantities by the automotive industry, reaching over 80% of use in cars according to WorldAutoSteel, aiming the weight reduction of the automotive body and increasing vehicle safety. It has higher mechanical strength compared to aluminum as well as lower cost. All these characteristics contribute to the automotive industry meeting its global targets for reducing pollutants. Due to the great importance that surrounds the development and optimization of current and new steels, this work has proposed to optimize the metallographic preparation method for the quantification of retained austenite by Electron Backscatter Diffraction (EBSD) in AHSS steel. The Rietveld method applied to X-ray diffraction was used as a reference in the present study. Two different final polishing techniques were applied by immersion in colloidal silica: Vibration polishing using the Vibromet machine and polishing using the Minimet machine. For each of those methods, the polishing time was varied. The results indicate that polishing using the Minimet machine is more efficient for this application. In addition, the EBSD method presented reliable results, close to the reference value, when the polishing method was efficient for the removal of the work-hardened layer by the previous steps of metallographic preparation.