In-situ study of discontinuous precipitation in Al-15 at.% Zn

The influence of Zn-concentration gradient on the occurrence of discontinuous precipitation has been analyzed in a Fe-13.5 at.% Zn alloy using the simulation method and Cahn′s diffusion model. The results have shown that the reaction front (RF) movement takes place by go- and -stop fashion accompanied by appropriate changes of Cahn′s parameter reaching maximum values, Cmax at the end of go- period. Then, the value of C decreases enabling relaxation of the RF and beginning of the next go- event. In this way, the simulation is the only one source of data showing how the solute concentration across the α phase lamella changes during the stop- period of the growth of discontinuous precipitates.The smaller thickness of the α phase lamellae and larger Cmax, the longer whole go- and –stop cycle, but not exceeding few seconds. The distance of RF movement is characterized by certain optimum value which is close to v = 45 nm/s regardless of the value of α phase lamella thickness.