Study on Weldability of Aluminium Alloy TL091 in Resistance Spot Welding with Intermediate Frequency and Direct Current

The resistance spot welding with intermediate frequency and direct current (RSWIFDC) was conducted to solve the weldability of the Al alloy TL091, The high-quality joint bearing dynamic load is realized for the first time by using the technique with the power of 2 kHz and the double-transformer based on the rapid response speed and stable welding current. By optimizing the welding process parameters, the strength, hardness distribution, microstructures and fracture morphologies of the joints were analyzed in details. The experimental results showed that the joints welded by the technique had better comprehensive mechanical properties, higher tensile strength and plasticity than that of the joints obtained by other spot welding. Shear fracture of the joints was seen at the nugget instead of the HAZ, thus indicating that the strength at the HAZ is higher than that at the nugget. The plastic ring of the joint was narrower as we desired. It was concluded that, by developing this advanced welding method and optimized welding parameters, high-quality joints were acquired to meet with higher design requirements of body-in-white of Al alloy under dynamic load. This is of great significance to the wide application of Al alloy body.