Microstructure and mechanical properties of tungsten inert gas welded–brazed Mg/Ti lap joints

Abstract

The tungsten inert gas (TIG) welding–brazing technology using Mg based filler was developed to join AZ31B Mg alloy to TA2 pure Ti in a lap configuration. The results indicate that robust joints can be obtained with welding current in the range of 60–70 A and welding speed of 0·2 m min⁻¹. The joints were found to be composed of the coarse grained fusion zone accompanied with the precipitated phase of Mg₁₇Al₁₂, and a distributed Mg–Ti solid solution zone at the interface of Mg/Ti, indicating that metallurgical bonding was achieved. The maximum tensile–shear strength of 193·5 N mm⁻¹, representing 82·3% joint efficiency relative to the Mg alloy base metal, was attained. The optimised Mg/Ti joint fractured at Mg fusion zone upon tensile–shear loading, mainly caused by grain coarsening. Moreover, the fracture surface practically consisted of scraggly areas, which was characterised by equiaxed dimple patterns accompanied with a few lamellar tearing.

Keywords:

• TIG welding–brazing
• Magnesium alloy
• Titanium
• Microstructure
• Mechanical property

Acknowledgements

The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (project no. 51205428) and the Fundamental Research Funds for the Central Universities (project nos. CDJZR13130040 and CDJZR12130047). The study was also supported by the sharing fund of Chongqing University’s large-scale equipment (project no. 2013063011).