While ultrasonics has been applied extensively to joining soft materials, such as copper and aluminum, for applications ranging from electronics to aerospace and automotive, applications for joining more advanced materials are limited. With the increased use of more advanced alloys, such as titanium, stainless steels, advanced high strength steels and nickel-base superalloys in critical applications, there exists a corresponding demand for capable welding processes. UMW has generally been thought of as not being viable for these advanced materials due to poor tooling life and inadequate ultrasonic power levels. In a relatively short period of time, significant developments in UMW equipment, along with the development of potential tool materials, may allow UMW to be applied to these more advanced metals.

Using commercially-available ultrasonic spot welding equipment, the ultrasonic weldability of type 304 and 410 stainless steel, commercially pure and 6Al-4V titanium, and Nickel-base superalloys 625 and 718 was investigated. Tool materials developed for friction-stir weld tooling were used to develop new ultrasonic tools. Tool textures and designs were also evaluated.