High-temperature Mechanical Behavior of Laser Welded Near α Ti60 Alloy

The high-temperature mechanical properties and deformation behavior of laser welded Ti60 alloy were investigated aiming at the high reliable service requirements of Ti60 laser welded structures for high thrust and high thrust/weight ratio aircraft. Results show that influenced by the welding thermal cycle, there are significant differences in the microstructure type, morphology, rare earth phase distribution, grain size, and volume fraction of recrystallization structure in different zones of welded joints. The average Vickers hardness can be ranked in terms of the decreasing value as weld zone > heat affected zone > base metal zone. The high hardness of the weld zone mainly arises from the fine needle α' phases. The high temperature induces the decrease of the hardness of different zones of joints by about 20%. The base metal is the failure path for welded joint specimens subjected to room and high temperature loading. The fracture surfaces are characterized by dimple growth induced transgranular fracture mode. The yield strength and tensile strength of welded joints are equivalent to those of the base metal. However, the elongation of welded joints is reduced. This can be attributed to the less deformation in weld zone and heat affected zone. The strength of the base metal and welded joints decrease when subjected to high temperature loading. The high temperature plastic deformation is mainly characterized by recovery and recrystallization induced strain softening.