Interface controlled precipitate dissolution and constitutional liquation

The paper reviews some of the kinetic aspects of second phase dissolution in binary and multicomponent systems, and relates them to the phenomenon of constitutional liquation, which is one of the causes of liquation in the subsolidus portion of the weld heat affected zone (HAZ) of these alloys. Particular attention is devoted to the concept of interface control during precipitate dissolution, and its effect on the extent and kinetics of constitutional liquation. It is shown that the presence of a sluggish interfacial reaction during precipitate dissolution has the potential to completely eliminate subsolidus liquation in the HAZ. Some of the conditions under which precipitate dissolution might become interface controlled are discussed. It is proposed that some of these variables can be controlled either through proper alloy design or through appropriate heat treatments, in order to develop microstructures which resist liquation in the subsolidus HAZ.