Mechanism of femtosecond laser ablating NiTi shape memory alloy

The mechanism of femtosecond(fs) laser ablating B2 NiTi alloy have been investigated by the molecular dynamic simulations combined with the two-temperature model. A series of simulations have been conducted, in which ,the laser used is 800 nm in central wavelength, 100 fs in pulse duration, and from 25 mJ/cm2 to 50 mJ/cm2 at fluence. The target is 90 nm in depth. The fluence threshold for 100 fs pulsed laser ablating NiTi shape memory alloy is determined, and it is found that the target irradiated by threshold fluence is ablated wholly due to the tensile and the heat induced phase change area is the smallest. When the fluence is improved, the phase change area expanded.