The École Nationale Supérieure de Mécanique et d'Aérotechnique (ISAE-ENSMA)is a grande école founded in 1948 and located near Poitiers, France.Graduates generally work as R&D engineers for corporations in the aerospace (60%), transportation, capital goods, and energy industry. The school is part of GEA, CESAER, PEGASUS and the ISAE group with the Institut supérieur de l'aéronautique et de l'espace (ISAE-SUPAERO). It is a member of Leonardo da Vinci consolidated University, an association of educational institutions in the former Centre, Poitou-Charentes and Limousin regions.
A series of experiments investigating the recrystallization (RX) mechanisms of the single-crystalline superalloy AM1 during its manufacture have been carried out. High and very high-temperature tensile tests were conducted to investigate the effect of the level of plastic deformation and the temperature at which the strain was applied. These parameters were then analyzed for their influence on RX mechanisms during the subsequent solution heat treatment. The strain threshold for RX under various temperature ranges has been determined, and it has been shown that RX is more likely to occur within the 900 °C to 1150 °C deformation temperature range. Some correlations between deformation mechanisms and volume fraction of γ′ in this type of alloy over these temperature ranges have been discussed in order to explain these trends. In addition, non-isothermal tensile tests were conducted to reproduce as closely as possible the thermomechanical path experienced during the manufacturing of single-crystalline parts using investment casting. A strong correlation has been demonstrated between the thermomechanical path followed during non-isothermal tests that lead to the appearance of recrystallized grains and the “recrystallization zone” identified from pure isothermal tests. This correlation becomes evident when the thermomechanical path crosses this zone. The effect of non-isothermal thermomechanical loading on microstructure was studied by EBSD analysis. Significant local misorientation was observed around microstructural inhomogeneities such as casting pores and eutectic/casting pore pairs. These local rotations suggest that microstructural inhomogeneities act as stress concentrators leading to the first RX nuclei once a super-solvus solution heat treatment has been applied.
This work aims at producing a gradient of atomic oxygen on a scale of 10 cm in a plane-to-plane nanosecond discharge in 150 mbar of air with a varying gap size for applications in combustion and ignition of detonation waves. Local measurements of atomic oxygen density along the discharge span, at varying heights between high-voltage and grounded electrode, are performed with Xe calibrated O-TALIF and validated by 2D numerical modelling. They both show existence of a gradient of atomic density of oxygen along the span. Reduced electric field is measured with two experimental techniques: optical emission spectroscopy by a spectral band intensity ratio of the first negative system and the second positive system of nitrogen, and E-FISH. It is also compared with numerical modelling. All techniques show existence of a gradient of reduced electric field along the span. This distribution of reduced electric field, in combination with the non-uniform energy deposition in the plasma, is shown to explain the measured gradient of density of atomic oxygen.
