The kinetics of the discontinuous precipitation and dissolution in Mg-richAl alloys

The morphology and growth kinetics of the discontinuous precipitation and d issolution reactions in supersaturated Mg-Al solid solutions containing 7.3 , 9.1 and 10.9 at % Al have been investigated by optical and scanning elect ron microscopy and X-ray measurements. The volume fraction of regions trans formed by the discontinuous precipitation reaction, the reaction front velo city, the interlamellar spacing and the average composition of the solute-d epleted lamellae were determined as a function of the temperature. For the first time, the kinetics of the discontinuous dissolution reaction has been studied in the Mg-Al system. It has been shown that the transport of the s olute atoms during both reactions is governed by grain boundary diffusion. (C) 1999 Kluwer Academic Publishers.