Effect of Pulse Energy on the Microstructure and Mechanical Properties of the Non-Optical Contact Femtosecond Laser Welding of Quartz Glass and the TC4 Alloy

Currently, the quartz glass–TC4 dissimilar joint has been applied in fields such as radiation environment testing, reactor engineering, and other areas. However, the high brittleness of the quartz glass and thermal mismatch during the welding process limit require further development. Thus, a femtosecond laser was employed to perform the direct joining of these materials under non-optical contact conditions, with the aid of a well-designed clamp and optimized process, and the effect of pulse energy on the microstructure and mechanical properties was analyzed. It was revealed that a lot of welding zones form at the interface through the diffusion of Si, O, and Ti and, thus, consist of a stable joint. Element distribution is related to pulse energy, which can affect the composition of secondary phases in the weld zones. The maximum shear strength of joints was 10.4 MPa with laser pulses of 0.3 mJ, while a further increase in the pulse energy led to more defects and stress unevenness. These findings provide valuable insights into enhancing the reliability of metal–glass welding joints and the promotion of femtosecond laser technology.