Strength, fatigue strength and toughness of dissimilar Ti17–Ti64 linear friction welded joints: Effect of soft surface contamination and depletion of α precipitates

The effect of microstructure three dissimilar Ti17–Ti64 linear friction welded joints on the strength, fatigue strength and fracture toughness was studied. A special attention paid to role soft contaminants α precipitate depletion. Three were produced: one in as machined state after electrical discharge machining, ground prior welding, post-weld heat treated. weld centre zone (WCZ) exhibited an acicular entangled α' martensite with a Widmanstätten morphology Ti64 side fine equiaxed distorted β grains Ti17 side. depletion strengthening precipitates observed WCZ thermo-mechanically affected (TMAZ) For studied welding parameters, LFW self-cleaning mechanism failed extrude interface joint state. These related machining denominated due their relatively low melting point. defect layer formed that led pseudo-brittle at during tensile testing, cyclic loading testing. During testing failure occurred plastic deformation sometimes parent material (PM) TMAZ. Fatigue cracks initiated latter weak reduced strength. Compared PM, samples even without pre-crack also reduced. Failure highlighted unexpected colonies elongated dimples nucleated transgranular lines.