Effects of transient thermophysical properties in numerical simulation of femtosecond laser-irradiated Ni 3 Al and NiTi

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Abstract Femtosecond laser processing nickel-based alloys involves nonequilibrium energy transfer and phase change processes, which strongly depend on the transient thermophysical properties of electrons. However, the influence of temperature-dependent properties on femtosecond laser-induced melting and ablation remains insufficiently understood. In this work, the femtosecond laser processing of Ni 3 Al and NiTi is investigated based on the two-temperature model. Two thermophysical properties groups are considered, including empirical constant properties and temperature-dependent properties derived from first-principles calculations. The spatiotemporal distributions of electron and lattice temperature under femtosecond laser irradiation are simulated. The melting and ablation processes at different laser fluences are calculated based on the mechanism of latent heat and phase explosion. Furthermore, the calculated melting and ablation depths are compared with the experimentally measured and previously published results. The model based on transient properties predicts the earlier start moment and deeper depth of melting and ablation than that based on the constant model for NiTi. However, the simulation results based on both properties are relatively close to each other for Ni 3 Al. These findings highlight the importance of transient thermophysical properties in accurate description of femtosecond laser processing and require more efforts in the determination of transient electron properties.

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