Microstructural evolution and mechanical properties of electron beam welded dissimilar titanium alloy joints

The aim of this study was to analyze the microstructural changes of two dissimilar Ti-6Al-4V/Ti17 and Ti-6Al-4V/BT9 joints welded via electron beam welding (EBW), and establish the relationship between microstructure and properties. The results showed that the occurrence of phase transformation was mainly dependent on the peak heating temperature during EBW, and despite the same welding parameters the microstructures of two dissimilar joints were different except in the heat-affected zone (HAZ) on the Ti-6Al-4V side. Both dissimilar joints exhibited a higher strength compared with Ti-6Al-4V base metal (BM), and the strength of Ti-6Al-4V/Ti17 joint was slightly higher than that of Ti-6Al-4V/BT9 joint due to the presence of finer martensite. Fatigue life of dissimilar joints was almost the same as that of Ti-6Al-4V BM within the experimental scatter. Fatigue failure of both dissimilar joints occurred in the HAZ, and fatigue crack basically initiated from the specimen surface.