The Lockheed Martin Advanced Programs team has investigated the feasibility of friction stir welding (FSW) titanium 6Al-4V at 0.200-inch thickness.  Appropriate pin tool material and optimal processing parameters were determined.  Both thermal and environmental management systems were tested, and an A-basis design allowable was calculated for weld strength at cryogenic and elevated temperatures.

FSW of titanium 6-4 presents a number of challenges due to its high temperature strength and reactivity with other elements.  Pin tool survivability and compatibility is a critical consideration in the weld development process.  Thermal management concerns and the need for an inert weld environment must be addressed to promote weld stability and inhibit interstitial contamination.  Finally, to mature titanium 6-4 FSW into a viable production process, continually longer welds must be performed and an A-basis allowable strength value must be calculated.  A description of the approach taken to meet these challenges is presented.