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Papers by Gaspar González-Doncel

Journal of Applied Crystallography, May 29, 2023

The peak broadening in neutron diffraction experiments on tensile specimens of pure Al (99.8%) an... more The peak broadening in neutron diffraction experiments on tensile specimens of pure Al (99.8%) and an Al-Mg alloy pre-deformed at different creep strains is analysed. These results are combined with the kernel angular misorientation of electron backscatter diffraction data from the creep-deformed microstructures. It is found that differently oriented grains possess different microstrains. These microstrains vary with creep strain in pure Al, but not in the Al-Mg alloy. It is proposed that this behaviour can explain the power-law breakdown in pure Al and the large creep strain observed in Al-Mg. The present findings further corroborate a description of the creep-induced dislocation structure as a fractal, predicated on previous work.

Materials Science Forum, Aug 1, 2003

$Research paper thumbnail of Friction stir welding of thick plates of aluminum alloy matrix composite with a high volume fraction of ceramic reinforcement$

Composites Part A-applied Science and Manufacturing, Nov 1, 2013

Lecture Notes in Computer Science, 2021

Materiales Compuestos, Jul 3, 2019

Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Jan 28, 2005

Journal of Metastable and Nanocrystalline Materials, Apr 1, 2003

Trabajo presentado en el 9th International Symposium on Metastable Mechanically Alloyed and Nanoc... more Trabajo presentado en el 9th International Symposium on Metastable Mechanically Alloyed and Nanocrystalline Materials (ISMANAM), celebrado en Seúl (Corea del Sur), del 8 al 12 de septiembre de 2002ECAP (Equal Channel Angular Pressing) is a materials processing method that allows very high strains to be imposed, leading to extreme work hardening and microstructural refinement. The microstructure of an Al-Mg alloy is examined after processing by ECAP as well as its evolution during subsequent heat treatments for precipitation, recrystallization, or grain coarsening. Fine microstructures are produced by deformation which coarsen steadily on annealing. The grain boundaries present after deformation as well as after annealing are generally of very low angle misorientations, and different textures are obtained than after heavy deformation by conventional deformation processing. Much of the strengthening observed can be explained by Hall-Petch strengthening, with additional strengthening due to the high dislocation density of the deformed state.Peer reviewe

$Research paper thumbnail of Residual Stress Distribution after Quenching Treatment Obtained from Diffraction Experiments and Simulation by Finite Element Method$

Surface investigation: x-ray, synchrotron and neutron techniques, May 1, 2021

A model found by finite element method was developed in COMSOL Multiphysics to describe the evolu... more A model found by finite element method was developed in COMSOL Multiphysics to describe the evolution of residual stress after quenching of cylindrical samples of aluminium alloys AA2014 and AA5083. The treatment consisted of annealing followed by quenching in fresh water. The thermal and mechanical properties of both alloys at the annealing and room temperatures were taken into account. A different sample size was considered for each alloy. The simulations show that the residual stress strongly depends on the yield stress and sample size. The results obtained by the finite element method were compared with the experimental residual stress profiles calculated from neutron and X-ray diffraction data.

Philosophical Magazine Letters, Mar 1, 1993

... By GASPAR GONZALEZ-DONCEL Centro Nacional de Investigaciones Metalurgicas, Avenida de Gregori... more ... By GASPAR GONZALEZ-DONCEL Centro Nacional de Investigaciones Metalurgicas, Avenida de Gregorio del Amo 8, 28040 Madrid, Spain ... Typical values for n in pure A1 for dislocation creep are about four to five with Q between 82 and 142 kJ mol-I (Frost and Ashby 1982). ...

En este trabajo se intenta relacionar el comportamiento mecanico de distintas aleaciones de alumi... more En este trabajo se intenta relacionar el comportamiento mecanico de distintas aleaciones de aluminio con sus caracteristicas microestructurales. Consta de tres partes y en cada una de ellas se estudia una aleacion especifica. En la primera se estudia una aleacion comercial de Al-4% Cu. El trabajo se centra en el efecto de los precipitados sobre los cambios de orientacion y fractura de probetas monocristalinas. En la segunda parte se estudia el comportamiento superplastico de la aleacion comercial 7475. Se propone un unico modelo de deslizamiento de fronteras de grano que explica la fluencia del material en un amplio intervalo de temperaturas. Por ultimo, se estudia la evolucion de la textura de la aleacion Al - 5% Ca - 5% Zn de pequeno tamano de grano durante la deformacion por traccion en distintas condiciones de ensayo.

DOAJ (DOAJ: Directory of Open Access Journals), May 1, 1998

Materials Transactions Jim, 1989

$Research paper thumbnail of Relajación mediante recocidos de las tensiones residuales en materiales compuestos de matriz metálica: estudio por difracción de neutrones$

Metallurgical and Materials Transactions, Jul 1, 1996

ABSTRACT The present work is part of an investigation into the use of rapid solidification and po... more ABSTRACT The present work is part of an investigation into the use of rapid solidification and powder metallurgy techniques to obtain iron-boron alloys with good mechanical properties. Two Fe-B binary alloys and two ultrahigh boron tool steels were gas atomized and consolidated by hot isostatic pressing (HIP) at temperatures ranging from 700 °C to 1100 °C to have a fine microstructure. Optimum properties were achieved for the binary alloys at low consolidation temperatures, since the solidification mi-crostructure from the original powders is eliminated and, at the same time, fine microstructures and low porosity are obtained in the alloys. At high temperatures and low strain rates, three of the four alloys exhibited low stress exponents, but only the Fe-2.2 pct B alloy showed tensile elongations higher than 100 pct. At low temperatures, only the Fe-2.2 pct B alloy deformed plastically. This alloy showed values of tensile elongation and ultimate tensile strength that were strongly dependent on testing and consolidation temperatures.

Materials Letters, Apr 1, 2023

ChemInform, Aug 17, 2010

Al 2 O 3 /TiO 2 eutectics containing 62-64 wt% Al 2 O 3 were fabricated by a laser floating zone ... more Al 2 O 3 /TiO 2 eutectics containing 62-64 wt% Al 2 O 3 were fabricated by a laser floating zone method. Raman spectrometry was used to determine the phase composition. The compressive creep strength of AT36 (Al 16 Ti 5 O 34 / Al 2 O 3) crystal at 1500°C under the strain rate of 1.0 × 10 −4 s −1 has 372 MPa, which is about higher than β-Al 2 TiO 5 and β-Al 2 TiO 5 /Al 2 O 3 crystals. High-temperature flexural strength, elastic modulus, hardness and fracture toughness of the AT36 crystals were analyzed. The highest flexure strength at ambient temperature was found in the material with 36 wt% TiO 2. In addition, we briefly discussed the relationships between microstructure and mechanical properties in AT36 crystal.

Surface investigation: x-ray, synchrotron and neutron techniques, Jul 1, 2021

A method is proposed to calculate the microscopic residual stresses in extruded cylindrical sampl... more A method is proposed to calculate the microscopic residual stresses in extruded cylindrical samples of non-ageing aluminium alloy 5083 (Al–Mg), arising from quenching in fresh water from 530°C. We start from the premise that the alloy is single-phase and non-isotropic on a microscopic scale; it consists of many grains that exhibit different mechanical response depending on their crystallographic orientation and neighboring grains. Microscopic residual stresses depend on the applied heat treatment, microstructure and mechanical strength of the individual grains. The stresses were calculated from neutron diffraction data. Genetic programming algorithms were used to calculate microscopic residual stresses, considering that each diffraction peak describes the stress distribution of a group of grains having a certain orientation, size and environment. The algorithm assigns a stress value to each grain according to the distribution of the diffraction peaks and the microstructural parameters of these grains.