In this paper, we establish a physical model to simulate the melt ejection induced by millisecond pulsed laser on
aluminum alloy and use the finite element method to simulate the melting and vaporization process of aluminum alloy.
Compared with the conventional model, this model explicitly adds the source terms of gas dynamics in the
thermal-hydrodynamic equations, completes the trace of the gas-liquid interface and improves the traditional level-set
method. All possible effects which can impact the dynamic behavior of the keyhole are taken into account in this
two-dimensional model, containing gravity, recoil pressure of the metallic vapor, surface tension and Marangoni effect.
This simulation is based on the same experiment condition where single pulsed laser with 3ms pulse width, 57J energy
and 1mm spot radius is used. By comparing the theoretical simulation data and the actual test data, we discover that: the
relative error between the theoretical values and the actual values is about 9.8%, the melt ejection model is well
consistent with the actual experiment; from the theoretical model we can see the surrounding air of the aluminum alloy
surface exist the metallic vapor; an increment of the interaction time between millisecond pulsed laser and aluminum
alloy material, the temperature at the center of aluminum alloy surface increases and evaporation happens after the
surface temperature reaches boiling point and later the aluminum alloy material sustains in the status of equilibrium
vaporization; the keyhole depth is linearly increased with the increase of laser energy, respectively; the growth of the
keyhole radius is in the trend to be gentle. This research may provide the theoretical references to the understanding of
the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application
of the laser materials processing and military field.