Modeling the Microstructure Evolution During Laser Processing of Ti-6Al-4V
Authors:
Shawn Kelly, Applied Research Laboratory - The Penn State University; State College PA USA
S. Suresh Babu, Oak Ridge National Laboratory; Oak Ridge TN USA
Stephen Kampe, Materials Science and Engineering Dept., Virginia Tech; Blacksburg VA USA
Presented at ICALEO 2005

Near-net shape processes, such as laser metal deposition (LMD), offer a unique combination of process flexibility, time savings, and reduced cost in producing titanium alloy components. The current challenge in processing titanium alloys (Ti-6Al-4V) using LMD is in understanding the complex microstructure evolution in a part fabricated layer by layer. The microstructure is affected by the repeated thermal cycling into the ? and ?+? phase fields during the deposition of multiple layers of material. A microstructure model that predicts the ? phase fraction and morphology evolution was constructed using thermodynamic and kinetic models to quantify the effect of thermal cycling on the as-deposited microstructure evolution. When applied to computed thermal cycles for LMD of Ti-6Al-4V, the microstructure model is in qualitative agreement with the as deposited microstructure. The model predicts greater amounts of colony-? formation during a thermal cycle just below the beta transus, as observed in the as-deposited material.