Abstract The δ is an important stable phase that replaces the metastable γ'' in the microstructure of Inconel 625 superalloy. The present work aims to investigate the kinetic of δ-phase precipitation in the microstructure of Inconel 625 nickel-based superalloy aged at 550, 625 and 725 °C up to 1000 h. Aging temperatures were chosen based on the thermodynamic simulation using JMatPro software which indicated that this phase is stable at temperatures below 905 °C. Microstructure of the heat-treated samples was analyzed via SEM/EDS and microhardness evolution was performed by Vickers microhardness tests. The results have shown that the samples aged at 550 °C (all times), 625 °C (all times) and 725 °C up to 200 h did not presented microstructural evidences of δ precipitation. However, samples aged at 725 °C for 500 and 1000 h clearly presented an acicular δ-phase precipitated mainly at the grain boundaries. It was noted changes in the microhardness at different aging time and temperatures probably due to the presence of γ'' and/or δ phases. The sample aged at 625 °C for 1000 h presented the highest microhardness value (333 ± 10 HV).

Aluminum beverage cans should have very specific crystallographic textures to increase productivity, reduce losses and reduce the amount of material. The present work seeks to add information on the crystallographic texture of aluminum alloy 3104 H-19 during the different manufacturing steps, which undergoes a flat sheet of metal for a cylindrical body. The work scope encompasses from the cup drawing to the final ironing operation and its objective is to add information on the texture evolution of the aluminum alloy undergoes in the intermediary steps. Crystallographic texture continues to change from the drawn cup through the ironing stages. This rotation is assumed to be a grain alignment with the plastic flow of the material.

The aim of the present work was to investigate the effect of the treatment time on the surface chemistry and corrosion behavior of cerium-based chemical conversion coatings on the AZ91D magnesium alloy. The conversion coating was prepared by the immersion technique from a bath consisting of 0.05 mol.L-1 Ce(NO3)3.6H2O and 0.254 mol.L-1 H2O2 (30 wt.%) for times ranging from 20 s to 120 s. The surface chemistry was examined by X-ray photoelectron spectroscopy (XPS). The corrosion behavior was assessed by electrochemical impedance spectroscopy and potentiodynamic polarization. XPS analysis detected the presence of cerium oxides (Ce2O3 and CeO2) and cerium/magnesium hydroxides. The best corrosion behavior was observed for the treatment conducted for 60 s. The results are discussed with respect to coating morphology and composition.

RESUMO As condições operacionais impostas nos processos de fundição geram, como consequência direta, uma diversidade de estruturas de solidificação. Em geral, as propriedades mecânicas mostram-se fortemente dependentes da morfologia estrutural e da composição química. Um aço de baixo carbono foi utilizado para promover fluxo de calor unidirecional durante a solidificação e obter o arranjo da microestrutura. O objetivo deste trabalho é pesquisar a influência das variáveis térmicas de solidificação na microestrutura da liga Al-10%Si-2%Cu e na sua resistência mecânica. Resultados experimentais incluem os espaçamentos dendríticos primários (EDP), velocidade de deslocamento da isoterma liquidus (VL), taxa de resfriamento (TR) e limites de resistência à tração (LRT) e de escoamento (LE). Estruturas dendríticas mais grosseiras tendem a diminuir a resistência à tração e ao escoamento na liga em estudo.

ABSTRACT The imposition of a wide range of operational conditions in foundry and castings process generates, as a direct consequence, a diversity of solidification structures. The mechanical properties show to depend strongly on the structural morphology and chemical composition. A low carbon steel mold was used to promote a unidirectional heat flow during solidification and to obtain the arrangement of the microstructure. The aim of the present article is to investigate the effect of thermal solidification variables on the microstructure of the Al-10wt.%Si-2wt.%Cu alloy and its mechanical strength. Experimental results include primary dendrite arm spacings (EDP), tip growth rate (VL), cooling rate (TR) and tensile (LRT) and yield (LE) strength limits. A coarser dendritic structure tends to improve the tensile strength and the yield tensile strength in the studied alloy.