TY - JOUR A1 - Bruno, Giovanni A1 - Fernández, R. A1 - Gonzáles-Doncel, G. T1 - Fractal nature of aluminum alloys substructures under creep and its implications N2 - The present work offers an explanation for the variation of the power-law stress exponent, n, with the stress r normalized to the shear modulus G in aluminum alloys. The approach is based on the assumption that the dislocation structure generated with deformation has a fractal nature. It fully explains the evolution of n with r/G even beyond the so-called power law breakdown region. Creep data from commercially pure Al99.8%, Al-3.85%Mg, and ingot AA6061 alloy tested at different temperatures and stresses are used to validate the proposed ideas. Finally, it is also shown that the fractal description of the dislocation structure agrees well with current knowledge. KW - SSTC Model KW - Creep KW - Aluminum Alloys KW - Fractal Microstructure PY - 2018 U6 - https://doi.org/10.1063/1.5012035 SN - 0021-8979 VL - 123 IS - 14 SP - 145108-1 EP - 145108-8 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-44779 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bruno, Giovanni A1 - Fernández, R. A1 - Garcés, G. A1 - Nieto-Luis, H. A1 - Gonzáles-Doncel, G. T1 - Fractional brownian motion of dislocations during creep deformation of metals N2 - The present work offers an explanation on how the long-range interaction of dislocations influences their movement, and therefore the strain, during creep of metals. It is proposed that collective motion of dislocations can be described as a fractional Brownian motion. This explains the noisy appearance of the creep strain signal as a function of time. Such signal is split into a deterministic and a stochastic part. These terms can be related to two kinds of dislocation motions: individual and collective, respectively. The description is consistent with the fractal nature of strain-induced dislocation structures predicated in previous works. Moreover, it encompasses the evolution of the strain rate during all stages of creep, including the tertiary one. Creep data from Al99.8% and Al- 3.85%Mg tested at different temperatures and stresses are used to validate the proposed ideas: it is found that different creep stages present different diffusion characters, and therefore different dislocation motion character. KW - Metals KW - Fractional brownian motion KW - Creep deformation PY - 2020 U6 - https://doi.org/10.1016/j.msea.2020.140013 VL - 796 SP - 140013 PB - Elsevier B.V. CY - Paris AN - OPUS4-51450 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -