How to suppress the Kirkendall porosity within the Ti/Ni explosive welds?

Abstract

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 °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 °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.