Gasless combustion in the combined binary mixtures formed by alternating non-activated and mechanically activated layers containing low-melting reagent was mathematically modelled in a macroscopic approximation, with account for a phase transformation (melting) in a low-melting reagent. The phase transition was found to either decelerate or accelerate combustion: the former happens when some amount of the reaction heat is spent on the recovery of a low-melting compound, while the latter takes place when melting occurs at lower temperatures and is accompanied by an increase in the interphase (contact) surface