Characterization of Al-Ni intermetallics around 30-60 at% Al for TLPB application

Interest on the Al–Ni equilibrium diagram along the latest years is associated with the attractive properties of its intermetallic phases, such as high thermal stability, high corrosion resistance and high strength to density ratio. The Transient Liquid Phase Bonding (TLPB) is a technological process which can be applied to manufacture new pieces and to perform reparations. Morphology, composition profiles, growth kinetic and hardness as a function of temperature and composition of the Intermetallic Layers (ILs) were analyzed, especially focused on solid–solid interactions during isothermal annealing in reactive diffusion couples Ni/Al (800–1170 °C). The study yields to the following association of the Al–Ni Intermetallic Phases (IPs) to the ILs: L1 (Al3Ni), L2 (Al3Ni2), L3 (Ni-poor AlNi), L4 (Ni-rich AlNi) and L5 (AlNi3). The composition ranges of L3 and L4 are 36–46 and 53–58 at% Al, respectively. Martensitic transformation was found in the half thickness of L4 (L4M and L4S) at 1170 °C. Kinetics show diffusion controlled growth for L2 and L5 and interface reaction control for L4 at 800–1170 °C, while L3 revealed a mixed kinetic behavior: parabolic at 800–1000 °C and linear at 1170 °C. The growth rate constants presented temperature dependence according to the Arrhenius model. Vickers microhardness values decrease with annealing temperature and Ni concentration for ILs, and put in evidence different mechanical properties of L3, L4M and L4S.Fil: Urrutia, Guillermo Alejandro. Universidad Nacional del Comahue; ArgentinaFil: Tumminello, Silvana Deisy Paulina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. IDEPA - Subsede San Antonio Oeste; Argentina. Universidad Nacional del Comahue; ArgentinaFil: Aricó, Sergio Fabián. Comision Nacional de Energia Atomica. Centro Atomico Constituyentes. Departamento de Materiales; ArgentinaFil: Sommadossi, Silvana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. IDEPA - Subsede San Antonio Oeste; Argentina. Universidad Nacional del Comahue; Argentin

Identification of precipitates in U-Nb-Zr alloys thermally treated at 850 °C

<p></p><p>ABSTRACT At the present, the international goal is to develop and qualify a very high U density fuel for high flux research reactors. The selected U-alloy must present an isotropic crystalline structure at the end of the fuel fabrication process. These types of structures exhibit stable behavior under irradiation. In particular, it is wanted to retain as metastable the γU phase (or some phase derivated of this). Several investigation lines are being developed in Argentina, regarding both dispersed and monolithic fuels. One of this lines is focused on development of U(Mo)/Zry-4 monolithic fuel. Simultaneously, the fabrication of U(Zr,Nb)/Zry-4 miniplates was started in 2005. As part of this last monolithic fuel development, 10 alloys with U densities between 7-10 gU/cm3 were fabricated. These alloys were homogenized in γU(Zr,Nb) phase by annealing at 850 ºC for 1 and 24 h and finished by quenching. In this work the morphological and crystallographic characterization of this set of alloys is presented. The major phases identified were: γU (Zr, Nb) (or the transition phase γS derived from it), δUZr2 and α” (transition phase derived from the equilibrium αU phase). In addition, four types of precipitates, rich in Zr, with different morphologies were identified. The presence of each of them was associated to the stage in which they were formed: during the casting process of the alloy, the heat treatment and / or the annealing process. This result allows us to evaluate which parameters need to be controlled to obtain a homogeneous alloy at the time of making a nuclear fuel.</p><p></p

Crystallographic characterization of Cu-In alloys in the 30-37 at.% In region

The Cu-In-Sn system is one of the Pb-free options to replace conventional Pb-Sn alloys in electronic industry. However, controversies still exist regarding some regions of the equilibrium phase diagram of the Cu-In-Sn ternary and also of the Cu-In and Cu-Sn binary systems. One of the most controversial fields of the Cu-In binary phase diagram lies between ~33 and 38 at.% In and temperatures ranging from 100 up to 500 °C. In this work, binary Cu-In alloys, with 30-37 at.% In nominal compositions and annealed at two different temperatures (i.e. 300°C and 500°C) for a long period (i.e. 7 months) were characterized by scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS) and X-ray diffraction (XRD). Three phases exist over the 33-38 at.% In composition range, namely the phase A at high temperatures and the B and C phases at low temperatures. These three phases can be described as superstructures of the hexagonal phase h (Cu2In) and differ, although slightly, from those previously reported in the literature. In addition, it has been demonstrated that even conventional XRD allows to unequivocally distinguishing between these phases despite their similar crystal structure.Fil: Baque, Laura Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Torrado, D.. Universidad Nacional del Comahue. Facultad de Ingeniería; ArgentinaFil: Lamas, Diego Germán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional del Comahue. Facultad de Ingeniería; ArgentinaFil: Aricó, Sergio Fabián. Comisión Nacional de Energía Atómica; ArgentinaFil: Craievich, A.F.. Universidade de Sao Paulo; BrasilFil: Sommadossi, Silvana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Universidad Nacional del Comahue. Facultad de Ingeniería; Argentin

Study of the U3Si5, USi2-x and USi2 phases stability due to the incorporation of aluminium in solution by the use of Differential Scanning Calorimetry (DSC) technique

<p></p><p>ABSTRACT U(Mo) alloys are being studied to be applied as a fuel for research and test reactors. When U(Mo) particles are dispersed in an Al matrix, it is known that an interdiffusion during fabrication process and / or irradiation. In this sense, irradiation tests have shown that this IL has a bad behavior under irradiation coming up the addition of Si to Al as one of the most promising solutions. Several out of pile experiences have been performed with U(Mo)/Al(Si) diffusion couples in which U(Al,SI)3, U3Si5, USi2, USi2-x, Al20Mo2U and/or Al43Mo4U6 are the phases identified as conforming the IL. In some cases, U3Si5 was identified considering modified lattice parameters, which can be justified assuming that the U3Si5 phase would accept a small amount of Al in solution. However, although the Al-Si-U ternary system has been extensively studied, there are no previous experimental results to correlate lattice parameters modification with Al solubility in U3Si5, USi2 y USi2-x phases. From previous paragraphs, it is important to study the Al-Si-U ternary system especially in the environment of U3Si5, USi2 and USi2-x phases. With this aim, ten alloys were fabricated. Nine of them were isothermally treated at 550 ºC and microstructurally characterized. The Main results show the presence of needle-like morphology in the alloys with concentrations around that of the U3Si5 phase. From th fact that this kind of morphologies is characteristic of a displacive transformation, which occur during cooling process, the use of a dynamic identification transformation technique (as differential scanning calorimetry) came up as mandatory in this research In this new stage, nine alloys were studied with the calorimeter using two heating/coolig rates (± 1 ºC/min and ± 10 ºC/min). Transformation temperatures and enthalpy of formation of compounds were determined. The samples were also microstructurally characterized after testing.</p><p></p