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Temperature-modulated dilatometry represents a powerful technique for studying kinetic processes in materials, such as, e.g., the equilibration of the concentration of thermally formed lattice vacancies in metals [1]. In the present work, the application potentials of this technique are explored with respect to precipitation kinetics in alloys. Al-Mg is used as case example, where the phase equilibration between the saturated solid solution Al(Mg) and the intermetallic Al3Mg2 phase is monitored [2]. Upon temperature modulation, the variation of relative phase fractions, which arises from the temperature-dependent Mg-solubility in Al, can be specifically detected by dilatometry due to the different atomic volumes of the intermetallic phase and the solid solution. The equilibration process causes a phase shift between the periodic length change and the applied sinusoidal temperature modulation, which gives access to the underlying kinetic processes. The measured variation of the phase shift with the modulation frequency is quantitatively analyzed in the framework of a simple kinetic model, revealing that the equilibration process is controlled by the diffusion of Mg in Al.
[1] R. Würschum et al., Int. J. Mater. Res. 113 (2022) 683.
[2] M. Simhofer et al., J.Alloys&Comp. 1010 (2025) 176984.