Linear Friction Welding of Ti-6Al-4V for Stanchion Components

The increasing use of composite materials observed in new aircraft builds leads to a significant demand for titanium alloy structural parts. The rising material costs and popularity, together with their restrictions in supply and processing, is driving the aerospace industry to make increasingly efficient use of available material.

Linear Friction Welding (LFW), a rapid, high integrity, solid-state forging process, has the potential to decrease the buy-to-fly ratio, production time and time to market of aerostructure components. It has already proven its dependability for the production of some of the latest generation aero engines.

The LFW process is not yet used for aerostructures. This is primarily due to the LFW process not being widely known, and not having been developed or proven for aerostructure applications; but also due to a lack of performance data on aerostructures manufactured by LFW being currently available to the aerostructure supply chain and design community.

To address this issue, a large series of Ti-6Al-4V weldments was produced and assessed via metallographic examinations and mechanical testing. The matrix of experiments was able to capture the LFW process window of this titanium alloy, and to measure the impact of the parametric conditions. Metallographic examination revealed a high integrity weld free from contaminants and oxides at the weld interface.

The metallurgy of the welds revealed a characteristic fine-grained equiaxed microstructure. As-welded joints were tested under tensile and alternating fatigue conditions to provide an extended set of joint performance data. Finally, a techno-economic assessment was conducted which demonstrated the viability and potential of the LFW process for a representative structural airframe stanchion component.