The microstructures associated with pulsed-laser heating of multilayer thin films used for phase-change optical data storage are studied in three related films. Two employ the multilayer structure SiOx/TeGeSn/SiOx where the chalcogenide layer is either amorphous or crystalline. The third uses the same trilayer structure with a crystalline chalcogenide layer but with an additional layer of aluminum. Pulsed-laser melting of micron-sized spots leads to solidification in the non-aluminized specimens with a morphology dependent on the preexisting structure of the chalcogenide layer and to amorphization in the aluminized film. Heat-flow modelling shows that the maximum temperature reached is lower and the cooling rate through the glass-forming temperature range higher in the aluminized structure. Discussion centers on the thermal and optical properties of the different films and the impact of the pre-existing chalcogenide structure on the subsequent phase transformations.