Thermal Effect System of NiTi Shape Memory Alloy under Femtosecond Laser Loading

In order to study NiTi shape memory alloy under extreme conditions of system temperature, two-temperature equation model was discussed under different approximate pulse width and energy density, laser electronic temperature and lattice temperature distribution under loading condition. Before loading, due to the loading time was short, the coupling items with heat conduction time space constraints imposed respectively. Using the finite difference method of femtosecond laser loading NiTi shape memory alloy to simulate one-dimensional dual temperature equation, respectively on the surface and bottom temperature system were analyzed. The results showed that the pulse width of 100 fs, the energy density of 400 J•m-2 squared femtosecond laser load under the condition of NiTi shape memory alloy electron temperature system peak after 0.184 ps, lattice after 0.273 ps peak temperature system, had certain hysteresis. At the same time, the laser energy density of electron temperature system was proportional to the lattice temperature system, laser pulse width of the electron temperature system was inversely proportional to the lattice temperature system respectively proportional relations. In the shorter the pulse width, alloy reached the ablation threshold energy density was lower. Due to the short loading time of the femtosecond layer, the temperature system of the alloy substrate changed slowly, and the propagation depth was within 50 nm. This result had important reference significance for the subsequent research on the characteristics of the alloy. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.