Análise da correlação entre as propriedades microestruturais e as propriedades mecânicas do aço AHSS DP800 após tratamentos térmicos

Abstract

This work aims to analyze the correlation between the microstructural properties and the mechanical properties of AHSS DP800 steel after the application of different thermomechanical treatments. Initially, test specimens were fabricated by cutting the material using a mechanical guillotine and a milling machine in the cutting and milling laboratories of the Mechanical Engineering course at IFPE – Recife Campus. The test specimens were subjected to specific thermomechanical treatments, where they were heated to 900°C for 30 minutes, followed by hot rolling and quenching, ending with a lead bath decomposition and cooling to room temperature. After the thermomechanical treatments, the mechanical properties of the test specimens were evaluated through tensile tests. Samples were also prepared for metallographic analysis using traditional techniques of grinding, polishing, and chemical etching, for microstructural analysis in a scanning electron microscope (SEM). The analysis revealed that, in some treatment routes, there was a significant increase in the mechanical properties of DP800 steel, correlated with the observed microstructural characteristics. However, other treatment routes resulted in a decrease in these properties. The results showed that the presence of ferrite and martensite in the microstructure of DP800 steel, after the thermomechanical treatments, was fundamental for the increase in the material's mechanical strength under certain conditions. The combination of these microstructural phases promoted the improvement of mechanical properties, demonstrating the effectiveness of the applied treatments. However, certain treatment conditions did not favor this improvement, leading to a decrease in mechanical properties.