Compositions, apparatus incorporating a composition, and methods of use are described, one composition embodiment consisting essentially of one or more reactive metals in major proportion, and one or more alloying elements in minor proportion, with the provisos that the composition is high-strength, controllably reactive, and degradable under defined conditions. Compositions of the invention may exist in a variety of morphologies, including a reactive metal or degradable alloy processed into an alloy of crystalline, amorphous or mixed structure that may constitute the matrix of other composition, for instance a composite. Methods of using apparatus comprising a composition, particularly in oilfield operations are also described (e.g. flow and displacement control, sensors, actuators). This abstract allows a searcher or other reader to quickly ascertain the subject matter of the disclosure. It will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).