Reinforcement of Mg/Ti joints using ultrasonic assisted tungsten inert gas welding–brazing technology

Abstract

Ultrasonic assisted tungsten inert gas welding–brazing technology was developed to refine coarsening columnar α-Mg grains of Mg/Ti joints. In this study, ultrasonic vibration was introduced into molten pool of Mg/Ti joints with frequency of 20 kHz and maximum power of 1·6 kW. The results showed that, with ultrasonic power of 1·2 kW, the morphology of columnar α-Mg grains was refined to approximately equiaxed grains and the average grain size of columnar grains decreased from 200 to ∼50 μm. Moreover, the maximum joint strength of joints increased ∼18·1% to 228 N mm −1 over the joints welded without ultrasonic vibration (193 N mm −1 ). Furthermore, the optimised Mg/Ti joint fractured at base metal zone rather than fusion zone upon tensile–shear loading, indicating that efficient grain refinement was attained. However, welding voids occurred with the ultrasonic power further increased to 1·6 kW, which resulted in the decrease in mechanical properties.