How to Suppress the Kirkendall Porosity Within the Ti/Ni Explosive Welds?

Pure Ti (Grade 1) and Ni (type Ni201) were used to produce the Ti/Ni welds employing the explosive welding process. Thermal expansion of the welded plates was determined using dilatometric measurements from room temperature up to 600 degrees C. The results showed that the thermal expansion coefficient of Ti/Ni welded plates is closer to that of pure nickel than would be suggested by the Timoshenko's model for bimetallic strip. The microstructure of the Ti/Ni interface after exposure to high temperatures revealed the presence of extensive interface porosity (Kirkendall porosity). This may cause a catastrophic disintegration of the weld during working or essential forming. The welded plates were annealed at the temperature of 650 degrees C under different applied compressive loads, and the applied load was shown to alter the microstructure of the NixTiy phases present at the Ti/Ni interface. Based on the obtained interface microstructural data, the strategy to suppress the Kirkendall porosity at the interface was proposed.