TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Fernández Serrano, Ricardo A1 - Saliwan-Neumann, Romeo A1 - Gonzalez-Doncel, Gaspar A1 - Bruno, Giovanni T1 - Dislocation substructures in pure aluminium after creep deformation as studied by electron backscatter diffraction JF - Journal of applied crystallography / International Union of Crystallography N2 - In the present work, electron backscatter diffraction was used to determine the microscopic dislocation structures generated during creep (with tests interrupted at the steady state) in pure 99.8% aluminium. This material was investigated at two different stress levels, corresponding to the power-law and power-law breakdown regimes. The results show that the formation of subgrain cellular structures occurs independently of the crystallographic orientation. However, the density of these cellular structures strongly depends on the grain crystallographic orientation with respect to the tensile axis direction, with (111) grains exhibiting the highest densities at both stress levels. It is proposed that this behaviour is due to the influence of intergranular stresses, which is different in (111) and (001) grains. KW - creep KW - pure aluminium KW - electron backscatter diffraction (EBSD) KW - cellular KW - structures KW - power law and power-law breakdown Y1 - 2022 U6 - https://doi.org/10.1107/S1600576722005209 SN - 1600-5767 VL - 55 SP - 860 EP - 869 PB - Munksgaard CY - Copenhagen ER - TY - JOUR A1 - Fernandez, Ricardo A1 - Gonzalez-Doncel, Gaspar A1 - Garces, Gerardo A1 - Bruno, Giovanni T1 - Towards a comprehensive understanding of creep BT - microstructural dependence of the pre-exponential term in Al JF - Materials science & engineering. A, Structural materials: properties, microstructure and processing N2 - We show that the equation proposed by Takeuchi and Argon to explain the creep behavior of Al-Mg solid solution can be used to describe also the creep behavior of pure aluminum. In this frame, it is possible to avoid the use of the classic pre-exponential fitting parameter in the power law equation to predict the minimum creep strain rate. The effect of the fractal arrangement of dislocations, developed at the mesoscale, must be considered to fully explain the experimental data. These ideas allow improving the recently introduced SSTC model, fully describing the primary and secondary creep regimes of aluminum alloys without the need for fitting. Creep data from commercially pure A199.8% and Al-Mg alloys tested at different temperatures and stresses are used to validate the proposed ideas. KW - creep KW - Aluminum alloys KW - dislocations KW - fractal KW - stress exponent Y1 - 2020 U6 - https://doi.org/10.1016/j.msea.2020.139036 SN - 0921-5093 SN - 1873-4936 VL - 776 PB - Elsevier CY - Lausanne ER - TY - GEN A1 - Müller, Bernd Randolf A1 - Kupsch, Andreas A1 - Laquai, Rene A1 - Nellesen, Jens A1 - Tillmann, Wolfgang A1 - Kasperovich, Galina A1 - Bruno, Giovanni T1 - Microstructure Characterisation of Advanced Materials via 2D and 3D X-Ray Refraction Techniques T2 - Materials Science Forum N2 - 3D imaging techniques have an enormous potential to understand the microstructure, its evolution, and its link to mechanical, thermal, and transport properties. In this conference paper we report the use of a powerful, yet not so wide-spread, set of X-ray techniques based on refraction effects. X-ray refraction allows determining internal specific surface (surface per unit volume) in a non-destructive fashion, position and orientation sensitive, and with a nanometric detectability. We demonstrate showcases of ceramics and composite materials, where microstructural parameters could be achieved in a way unrivalled even by high-resolution techniques such as electron microscopy or computed tomography. We present in situ analysis of the damage evolution in an Al/Al2O3 metal matrix composite during tensile load and the identification of void formation (different kinds of defects, particularly unsintered powder hidden in pores, and small inhomogeneity’s like cracks) in Ti64 parts produced by selective laser melting using synchrotron X-ray refraction radiography and tomography. KW - X-ray refraction KW - radiography KW - tomography KW - synchrotron X-ray refraction radiography KW - CT KW - microscopy KW - creep KW - porosity KW - damage evolution KW - additive manufacturing KW - metal matrix composite Y1 - 2018 SN - 978-3-0357-1208-7 U6 - https://doi.org/10.4028/www.scientific.net/MSF.941.2401 SN - 0255-5476 VL - 941 SP - 2401 EP - 2406 PB - Trans Tech Publications Ltd CY - Zurich ER - TY - JOUR A1 - Cabeza, Sandra A1 - Müller, Bernd R. A1 - Pereyra, Ricio A1 - Fernandez, Ricardo A1 - Gonzalez-Doncel, Gaspar A1 - Bruno, Giovanni T1 - Evidence of damage evolution during creep of Al-Mg alloy using synchrotron X-ray refraction JF - Journal of applied crystallography N2 - In order to provide further evidence of damage mechanisms predicted by the recent solid-state transformation creep (SSTC) model, direct observation of damage accumulation during creep of Al-3.85Mg was made using synchrotron X-ray refraction. X-ray refraction techniques detect the internal specific surface (i.e. surface per unit volume) on a length scale comparable to the specimen size, but with microscopic sensitivity. A significant rise in the internal specific surface with increasing creep time was observed, providing evidence for the creation of a fine grain substructure, as predicted by the SSTC model. This substructure was also observed by scanning electron microscopy. KW - aluminium alloys KW - creep KW - damage KW - synchrotron X-ray refraction KW - electron microscopy KW - subgrain structure Y1 - 2018 U6 - https://doi.org/10.1107/S1600576718001449 SN - 1600-5767 VL - 51 SP - 420 EP - 427 PB - International Union of Crystallography CY - Chester ER -