Rodrigo José Contieri

Super duplex stainless steels (SDSS) combine excellent mechanical strength and corrosion resistance but may undergo microstructural degradation when exposed to temperatures between 400 and 1010 °C, due to the precipitation of deleterious intermetallic phases such as the sigma (σ) phase. This study investigates the phase evolution in UNS S32750 SDSS subjected to aging treatments at 850, 900, and 950 °C for 10, 100, and 1000 min, followed by water quenching and furnace cooling. The surface and phase microhardness, as well as the volume fraction and average grain size of the σ-phase, were evaluated. The results showed an increase in microhardness with both temperature and aging time, reaching a maximum of 418 ± 4 HV₀.₅ under the 850 °C / 1000 min condition. The σ-phase volume fraction remained nearly constant after 1000 min, regardless of the cooling method, while grain growth exhibited a similar trend across the three evaluated temperatures. These findings enhance the understanding of σ-phase precipitation and dissolution mechanisms and provide valuable insights for defining optimal thermal parameters in welding and manufacturing processes involving UNS S32750 super duplex stainless steel.

Additive Manufacturing technology has continually advanced, allowing microstructure and property optimization. In recent years, several studies have been carried out with the aim of understanding mechanisms of formation and evolution of the microstructure and, consequently, their influence on mechanical properties. However, correlations between microstructure and corrosion properties are not completely understood, making more systematic investigations necessary. In this work, samples of the Ti-6Al-4V alloy were produced by combining different laser powers and scanning speeds in order to generate different energy density values (VED) with subsequent microstructures and properties. The samples were characterized by optical and scanning electron microscopy, hardness and relative density. Complementarily, corrosion tests were carried out. For the entire set of parameters used, the processed samples showed the formation of acicular martensite α´, followed by different levels of porosity depending on the applied energy density. VED proved to be an important control parameter, and the best combinations of hardness and corrosion resistance were obtained for the parameter ratio that generated energy densities greater than 100 J/mm³.

O trabalho de pesquisa trata-se do estudo de ligas de Titânio - Cobre, para aplicação na área biomédica. Há vários elementos de liga que quando combinados às ligas de Titânio melhoram suas propriedades, o Cobre é um deles, já que proporciona uma menor temperatura de fusão e consequentemente uma facilidade no processamento e fabricação das mesmas. Sendo assim, o presente estudo tem como intuito avaliar as diferentes composições de Cobre, através de diferentes rotas de resfriamento, bem como a análise das fases estáveis e metaestáveis processadas por fundição. A caracterização das amostras foi realizada por Difratogramas de Raio X e microscopia.