Fine grain titanium alloy is used extensively in aerospace and aircraft because of its excellent comprehensive properties and outstanding machinability.The evolution of phase,the effect of welding heat input on the grain growth in the coarse grain heat-affected zone(CGHAZ) and mechanical properties of welded joint during gas tungsten arc welding of ultra fine grain Ti-6Al-4V with lamellar microstructure were investigated.Measurement results indicate the severe grain growth coarsening in CGHAZ undergoing wel...