Comparative study of Oswald ripening and trans-interface diffusion-controlled theory models: Coarsening of γ′ precipitates affected by elastic strain along a concentration gradient

According to Lifshitz, Slyozov, and Wagner (LSW) and Trans-Interface Diffusion-Controlled (TICD) theoretical models, this paper reports the microstructure and its coarsening behavior of γ′ metastable-coherent precipitates in concentration gradient of Ni-13.75Ti (at%)/Ni generated by diffusion couple. The coarsening of precipitates was evaluated in two different Ti contents (R1-11.4Ti (at%) and R2-13Ti (at%)) generated along the concentration gradient and includes average size, size distributions and growth rate. The solvus and metastable-coherent bimodal lines as determined at 850 °C of 9.16 (at%) and 9.92Ti (at%) respectively by scanning electron microscopy. This paper suggests that elastic strains produced by the matrix/precipitate lattice mismatch caused significant deviations between the experimental results and those predicted by the LSW or TIDC theories. Activation energies for TIDC (Q_i) and LSW (Q_r) are Q_r: 219.69 and 172.61 kJ mol^-1 for R1 and R2 regions, respectively, and Q_i: 218.46 and 164.56 kJmol^-1 for R1 and R2 regions, respectively. A concentration gradient allows the study of various alloys with different concentration and volume-fraction in a single sample.