Microstructure and mechanical properties of friction- and electron-beam welded Ti–6Al–4V and Ti–6Al–2Sn–4Zr–6Mo

Abstract

This work presents mechanical data and microstructural characterization of friction welded (FRW) and electron beam welded (EBW) post weld heat treated (PWHT) specimens of Ti–6Al–2Sn–4Zr–6Mo and Ti–6Al–4V. PWHT Ti6246/Ti6246 welds and Ti64/Ti6246 welds were evaluated with tensile-, creep-, Charpy-V, and microhardness tests. The PWHT treatments were 593°C/2h, 640°C/2h and 704°C/2h, respectively. The microstructure of the different weld types and alloy combinations where examined and characterized using optical microscope and SEM.Tensile strength and yield strength were within specification for both material combinations. The elongation for Ti6246 welded to Ti6246 is below specification. Only small variations in tensile properties were found for the different PWHTs. Fracture occurred in base material of the Ti64 alloy for the combination of Ti64 welded to Ti6246.Charpy-V tests shows that the welds are more brittle compared with the base material. The largest difference was found in Ti6246 welded to Ti6246.No significant variation in creep properties for the different PWHTs has been found. Ti64 welded to Ti6246 shows poor creep properties due to the high testing temperature for the Ti64 alloy. Ti6246 welded to Ti6246 shows good creep properties compared to the base material.The general trend for the weld microhardness was a decreasing hardness with increasing PWHT temperature. One exception though was the FRW Ti64/Ti6246 combination, were the hardness of the Ti6246 side of the HAZ, close to the interface between the two alloys, was highest after a PWHT temperature of 593°C, then decreasing in hardness for 640°C, not PWHT and being least hard for the PWHT temperature of 704°C. The hardness of the Ti64 base material showed no decrease after the PWHTs, but the hardness of the Ti6246 bulk material decreased after PWHT at 704°C.