Friction stir processing of laser metal deposited Ti-6Al-4V

Laser metal deposition (LMD) can form near net shaped components for aerospace applications. Ti-6Al-4V is a widely used aerospace alloy and fabrication of this alloy using LMD is gaining popularity. Improved mechanical properties are always a requirement in aerospace alloys and research is constantly being conducted to improve the properties of components formed from this alloy. Friction Stir Processing (FSP) in the past has been used as a method to change the surface properties of materials through microstructural modifications. The changes in properties can include hardness, corrosion resistance, fatigue strength, etc. The first section of this thesis is based on a similar concept to modify the surface properties of the laser deposited Ti-6Al-4V through FSP. Microstructural changes in the Ti-6Al-4V laser deposits due to FSP and subsequent laser deposition has been presented. The microstructure was characterized by the SEM and optical microscope. Variations in the microhardness inside the nugget region have also been discussed. The second section of the thesis proposes a methodology to create a fully forged, recrystallized structure by integrating the hybrid laser deposition system and FSP. Various FSP parameters investigated in attaining the same have been discussed. The effective nugget region which was left unaffected due to the subsequent single, double and triple layer laser deposition has also been presented --Abstract,page iv