Microstructural evolution and mechanical properties in laser beam welds of Ti-2Al-1.5Mn titanium alloy with transversal pre-extrusion load

摘要

A method for reducing the underfill rate of welded joints is proposed, which is based on the application of a transversal pre-extrusion load during pulsed laser beam welding of titanium alloy. Underfill defects can be reduced or even eliminated by welding with a pre-extrusion load. Furthermore, the microstructural evolutions and mechanical properties of joints with/without transversal pre-extrusion load are analyzed. The results show that the microstructural evolutions in the fully transformed heat-affected zone (FTHAZ) are mainly related to the pre-extrusion loads and the micro-hardness decreases sharply when welding with a pre-extrusion load in FTHAZ. The lamellar structure growths change from parallelly to intricately in the fusion zone (FZ) under a pre-extrusion load; the grain size and misorientation distributions are also different when welding with a pre-extrusion load at the given welding conditions.