Influence of Wire EDM on Fracture Toughness of TI6AL4V

Grade 5 titanium (Ti6Al4V) is considered as the workhorse titanium alloy. It is widely termed an aerospace alloy and is a relatively new engineering material. One of the major challenges in the use of this aerospace material is its machinability. Its high strength which is maintained at elevated temperatures, low thermal conductivity, low elastic modulus and high reactivity with oxygen is a perfect recipe for machining challenges. This leads to high tool wear and long production times. Such challenges can be overcome by electrical discharge machining (EDM). Given that titanium is usually applied to mission critical components (gears, shafts, wing sections etc.), it is important to understand the possible effect of wire EDM (WEDM) on their structural performance. The purpose of this chapter is to present critical issues related to the effect of wire EDM on the fracture toughness of this aerospace material. EDM and WEDM processes are discussed. Their effects on the structural integrity of Ti6Al4V are then demonstrated through fracture toughness measurements. Four specimens were produced using wire EDM. This includes the pre-crack which is usually introduced by fatigue cycling. Obtained results indicate a slight decrease in fracture toughness compared to that reported in literature. It was also concluded that wire EDM technique can be used as an alternative to fatigue pre-cracking in fracture toughness testing of Ti6Al4V.