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Duplex stainless steels are austenitic-ferritic alloys used in many applications, thanks to their excellent mechanical properties and high corrosion resistance. In this work, chemical analyses, x-ray diffraction, and magnetic force microscopy (MFM) were employed to characterize the solution annealed and aged duplex stainless steel. The samples exhibited no changes in lattice parameters and the MFM technique proved successful in clearly imaging the magnetic domain structure of the ferrite phase.

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An investigation was made into the thermal stability and mechanical behavior under nanoindentation of a new glassy alloy with composition Ni 50 Nb 28 Zr 22 , produced in the form of melt-spun ribbons and copper mold-cast wedges. The alloy composition was designed based on the lambda criterion combined with the electronegativity difference among the elements. X-ray diffraction and scanning electron microscopy confirmed that the ribbons and wedges (up to 200 μm in thickness) are amorphous. The thermal properties of these samples were evaluated by differential scanning calorimetry (DSC). Nanoindentation revealed that the hardness of this alloy, around 10 GPa, is among the highest reported for metallic glasses. Remarkably, the cast wedge exhibits greater hardness and higher elastic modulus than the ribbon. This correlates with the larger amount of frozen-in free volume in the ribbons than in the cast wedges, as evidenced by DSC. In addition, finite element simulations of nanoindentation curves were performed. The Mohr-Coulomb yield criterion allows for better adjustment of the experimental data than the pressure-independent Tresca yield criterion. The simulations also reveal that the cohesive stress in the ribbons is lower than in the wedges, which explains the difference in hardness and Young's modulus between the two samples.

Nesse trabalho, a microscopia de varredura por sonda (Scanning Probe Microscopy -SPM), nos modos contato (Atomic Force Microscopy -AFM) e de força magnética (Magnetic Force Microscopy -MFM), foi utilizada para analisar a microestrutura de um aço inoxidável dúplex 2205 solubilizado e envelhecido. Foi feita uma aná-lise por AFM da superfície do aço solubilizado após crescimento de filme passivo. Por AFM, obteve-se indicação de crescimento de filme sobre a microestrutura do aço solubilizado, enquanto por MFM a distribuição de fases pôde ser observada sem a necessidade de ataque da superfície.Palavras-chave: Aço inoxidável dúplex, crescimento de filme, SPM, microestrutura. Abstract In this work, Scanning Probe Microscopy (SPM), in the contact (Atomic Force Microscopy -AFM) and magnetic force (Magnetic