M. Nunn, P. Threadgill, TWI Ltd, Cambridge, United Kingdom; J. G. Perrett, TWI Technology Centre (Yorkshire) Ltd, Sheffield, United Kingdom

Summary:

Many components in aerospace and other industries are machined from large blocks of material, resulting in wastage of over 80% of the material in many cases. Traditional near net shape approaches based on fusion processes have been available for a long time, but the deposition rates of these is generally rather slow, limiting the size of the components.

The use of various friction welding processes (e.g. friction stir welding, linear friction welding, rotary friction welding etc.) can be exploited to provide rapid manufacture of components which then require reduced machining. The high power equipment now available allows very rapid build up of machining blanks. For example, 7xxx alloys can be built up by friction stir welding in thickness of at least 25mm per pass, and this figure is set to increase significantly in 2005. It is also possible to incorporate different alloys into the structure.

A further potential advantage of the approach is that friction welding/processing will produce a very fine microstructure in much of the finished component.

The concept is being developed initially for high strength alumininium alloys (e.g. 2xxxx and 7xxxx alloys,) but is also feasible for titanium alloys, and with some further development for nickel based alloys.

The presentation will summarize knowledge available in this field, and show examples of what can be achieved. Some discussion of the advantages and disadvantages of the approach will also be discussed.