Micropyretic synthesis of tough NiAl alloys

NiAl has been produced by micropyretic synthesis in a tougher state by adding Cr, V, and Fe. The mechanical properties of the alloys have been evaluated. Fracture toughness values as high as 9.5 M Pa√m have been obtained. The effect of different process variables like particle size, diluents, and extent of preheat on the process of synthesis and the microstructure have been ascertained. Diluents, when present in small quantities, have been found to enhance the combustion process in NiAl without significantly affecting the microstructure of the alloy. Preheating of the specimen prior to synthesis however had a profound influence on the microstructure. The microstructures of the alloys have been examined for chemical homogeneity and the defect structure. The sequence of steps leading to the formation of NiAl from elemental powders during the process of micropyretic synthesis has been determined.