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In situ superconducting quantum interference device magnetometry provides insights into the electrochemical dealloying mechanism of a CoPd alloy. Charge-dependent measurements of magnetic moment allow the separation of primary and secondary dealloying contributions. Coercivity evolution revealed the transition from collective ferromagnetism to superparamagnetism of small alloy clusters evolving in the dealloying process, which is interpreted as an "inverse" magnetic percolation problem. Temperature-dependent magnetization curves enable a qualitative comparison of magnetic cluster size distributions in the nanoporous Pd framework, which are found to be strongly influenced by dealloying potential. The study underlines the potential of electrochemical dealloying as a promising method for the preparation of tailor-made magnetic nanostructures. [ABSTRACT FROM AUTHOR]

The Nd self-diffusivity has been studied in nanocrystalline Nd-rich Nd2Fe14B. From the analysis of the diffusion profiles grain-boundary diffusion coefficients DGBNd are derived similar to the values observed recently for 59Fe diffusion in this material. Above the intergranular melting transition, a second diffusion path indicates rapid diffusion in the liquid intergranular phase. [ABSTRACT FROM AUTHOR]

An in-depth case study of precipitation kinetics for alloys is presented utilizing recent progress in high-precision isothermal dilatometry by measuring relative length changes down to the range of 10-5 and covering large timescales exceeding 105 s. Using a dilute Al-Mg-Si alloy as model system, the different phases that form during isothermal heat treatment could quantitatively be analyzed both with respect to the absolute amount of precipitates and with respect to the underlying kinetics. Owing to the distinct length change features upon multi-step precipitation processes, the formation of the metastable β′′- and β′-phases can unambigously be detected and furthermore can specifically be distinguished and resolved. From the reaction rate analysis of the precipitation-induced relative length change, that was isothermally measured for temperatures between 170 ∘C and 260 ∘C, the evolution with time of the atomic fraction of both the β′′- and the β′-phase was determined. The results were also used to construct the isothermal time-temperature-precipitation diagrams which are important for technologically relevant processes. [ABSTRACT FROM AUTHOR]

Deals with a study which examined thermal vacancy formation and positron-vacancy interaction in Ti[sub3]Al at high temperatures. High-temperature positron lifetime studies on Ti[sub3]Al; Nearest-neighbor bond model calculations on the defect formation in Ti[sub3]Al; Summary and conclusions.

Deals with a study which investigated the correlation between the kinetics of the amorphous-to-nanocrystalline transformation and the diffusion in alloys. Experimental results and discussion; Summary and conclusions.

A kinetic model for the diffusion-controlled annealing of excess vacancies under the experimentally relevant, non-isothermal condition of time-linear heating is presented and applied to dilatometry. The evolution of the vacancy concentration with time is quantitatively analyzed, considering as ideal sinks either dislocations or grain boundaries of spherical- or cylindrical-shaped crystallites. The validity of the model is tested using dilatometry data that were obtained for ultrafine-grained Ni prepared by high-pressure torsion. The entire two-stage annealing curve of the dilatometric length change can be analyzed by combining the present kinetic model of vacancy annealing at grain boundaries with established non-isothermal kinetics of recrystallization. [ABSTRACT FROM AUTHOR]