Ultrafast laser-induced transient evolution mechanism of ablation and shock wave in titanium alloys.

Understanding ultrafast laser interactions with titanium alloys is critical for applications like precision machining and laser shock peening. Using a pump - probe shadowgraphy, we track the transient evolution of ablation and shock waves over delay times from 0.5 to 1600 ps. Three stages are identified: energy relaxation (0.5-1 ps), rapid material ejection (3-300 ps), and the formation of a stable ring structure after 500 ps. Ablation morphology depends strongly on laser parameters: pulse energy controls ablation diameter, while pulse duration and impact time govern depth. Shock wave expansion, propagation velocity, and pressure distribution also vary with laser settings, with the initial mechanical shock pressure up to 130.3 GPa. These results clarify ultrafast laser-matter dynamics and support optimization of laser processing parameters.