Browsing by Author "Ruano, Oscar A."
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Item Development of a 2.25%Cr steel P23 reinforced with micro/nano-carbide particles produced by self-propagating high-temperature synthesis(Trans Tech Publications Ltd, 2017) Carsí, Manuel; Jimenez, Jose A.; Gomez-Mitxelena, Xabier; Ruano, Oscar A.; Sommitsch, Christof; Ionescu, Mihail; Mishra, Brajendra; Mishra, Brajendra; Kozeschnik, Ernst; Chandra, T.; EXTREMATIn the present work, 1 wt.% of (Ti,Nb)C carbide particles prepared by self-propagating high temperature synthesis (SHS) were introduced into a melt of a conventional P23 steel to obtain a reinforced material with improved creep properties. The as-cast material showed a eutectic type microstucture, indicating partial dissolution of these carbides in the melt. Inside the dendritic regions, a bainitic/martensitic structure similar to that of the unreinforced material was present. A significant refinement of the prior austenitic grain size was revealed in the reinforced material. Brinell hardeness measurements reveal an increase of hardness in the reinforeced material due to the addition of the carbides. High strain rate compression tests were perfomed at temperatures in the range 950 and 1250ºC to determine the optimum forming conditions. Stability maps for a wide range of temperatures and strain rates were drawn. The optimum temperature for the reinforced steel is about 77 K higher than for the non-reinforced steel.Item Hot forging of a Cu-Al-Ni-Fe-Mn alloy and its simulation by torsion testing(2000-12) Carsí, Manuel; Peñalba, Felix; Rieiro, Ignacio; Zapiráin, Felix; Ruano, Oscar A.; Centros PRE-FUSION TECNALIA - (FORMER)The forming behavior of a Cu-Al-Ni-Fe-Mn alloy has been investigated. High temperature compression tests were carried out to test the forgeability conditions of this alloy. The microstructure of the deformed material is compared with that of the as-cast condition. Torsion tests were also performed at temperatures in the range 1023 to 1173 K to simulate the hot forging of a bearing under comparable conditions of temperature, strain rate and strain. The parameters of the Garofalo equation were calculated from the experimental torsion data to describe the deformation behavior of the alloy at various temperatures and strain rates. In addition, a study of the energy efficiency and maximum stability was made to determine optimal forgeability conditions for the forming process.Item Modelling the optimum hot workability of TiB reinforced Ti-6Al-4 V alloy by stability maps(2016-02-17) García de Cortázar, Maider; Peñalba, Felix; Silveira, Elena; Gómez-Mitxelena, Xabier; Carsí, Manuel; Ruano, Oscar A.; Tecnalia Research & Innovation; CIRMETAL; Caracterización y Validación. Materiales; EXTREMATHot workability of Ti-6%Al-4%V and two whisker discontinuously reinforced materials, Ti-6%Al-4%V/1.2%TiB and Ti-6%Al-4%V/8.9%TiB, have been investigated. Hot uniaxial compression tests were carried out using a computer controlled thermomechanical simulator Gleeble machine at temperatures in the range 850 °C to 950 °C and strain rates ranging from 1 to 50 s−1. The microstructures and the compression test results were compared among the three materials. The Ti-6%Al-4%V/8.9%TiB material presented extensive cracking after deformation. In contrast, the Ti-6%Al-4%V/1.2%TiB material showed an interesting compromise between flow stress and workability. The parameters of the Garofalo equation were calculated for the three materials revealing apparent activation energies that increased with increasing TiB content. The modelling is carried out by stability maps that gives the temperature at a given strain rate to obtain optimal workability and the stresses that has to bear the equipment. Taken 5 s−1 as a reference strain rate, the temperature required to obtain a quality product increased from about 1143 K (870 °C) for the Ti-6-4 alloy without TiB to 1228 K (955 °C) for the 1.2%TiB and to 1283 K (1010 °C) for the 8.9%TiB material. Therefore, the production of parts of the TiB composites should be conducted at a higher forming temperature to avoid the presence of cracks