Nowadays, many efforts have been concentrated in research and development of hydrogen absorbing materials due to a possible application as electrode for rechargeable batteries, on board hydrogen storage systems, getters, catalysts, etc. Novel technologies for materials processing have been used to generate new alloys with metastable structures, such as amorphous and/or nanocrystalline alloys. In this context, mechanical milling or mechanical alloying is a very attractive way to produce this alloys, specially when carried out under hydrogen atmosphere (reactive milling). In this work, we have studied the structural evolution of a TiCrV bcc solid solution during mechanical and reactive milling. The process parameters analyzed were: milling atmosphere (argon and hydrogen), milling time and gas pressure into the vials (in the case of reactive milling). Structural evolution was investigated by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM). Hydrogen contents of the reactive milled alloys were determined using a Leco analyzer. Differential scanning calorimetry (DSC) was used to determine the hydrogen desorption temperature and the stability of the alloys.
Creep-fatigue interaction has been studied in single crystal and equiaxed Ni based superalloys, adopted for critical gas turbine component applications. Cyclic hold tests have been performed to understand the influence of creep damage and deformation on fatigue endurance, considering also the effect of the position of the hold time in the low cycle fatigue cycle. Service-like thermomechanical fatigue (TMF) benchmark tests have been carried out, involving TMF cycles based on the loading conditions at component critical locations determined by finite element (FE) simulation. Damage calculations have been performed on all the conducted tests for both materials, comparing results obtained by different methodologies (e.g. time fraction, ductility exhaustion, strain energy density). The results have been compared with actual in-service damage revealed by microstructural examination.
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