Process and mechanism of selective micro-joining of glass-ceramic/metal heterostructures using ultrafast lasers

Ultrastrong Fe¨C36Ni alloy/glass-ceramic joints were successfully fabricated using ultrafast laser micro-welding technology with the aid of material ablation threshold regulation strategy for the first time. High-aspect-ratio LiAlSi2O6 whiskers were identified at the interface. The microstructural evolution and strengthen effects to the ultrafast laser micro-welds was systematically investigated. As the laser energy density increased from 1.16 J/cm2 to 5.41 J/cm2, the micro-welds morphology changed from metal-dominated thermal conduction behaviors (splashing, wetting, and adhesion) to nonlinear absorption-dominated mechanical interlocking with volcanic-like features. With the increase of laser energy density, the length and width of LiAlSi2O6 whiskers in the micro-welds increased and interlaced each other to form a mechanical interlock structure, resulting in a maximum shear strength of 44 MPa. This demonstrates the strengthen effect of the whiskers on the joint strength. The findings hold significant implications for ultrafast laser welding technology between glass-ceramic and metal, providing technical support for the fabrication of high-performance space mirror components.