A structure includes a substrate of a first material and a second material coating at least a portion of the substrate, where the second material is different from the first material, where the first and second materials, upon being thermally energized, react with each other in an exothermic and self-sustaining alloying reaction that propagates from a first location within the structure along a travel path to a second location within the structure at a rate that depends upon one or more characteristics of the first and second materials.