Analysis of molten pool dynamics and surface smoothing time scale in laser polishing alloy materials

•The concept of surface smoothing time scale (SSTS) is proposed for the first time to calculate the process window of laser polishing.•For Ti6Al4V and other metallic materials with a similar dynamic viscosity, the value of SSTS is hundred microseconds level.•There is only one SSTS corresponding to an optimal laser-material interaction duration for a certain laser power density because of Marangoni effect.•Experiments verified that the optimal combination of processing parameters can be found through the SSTS theory.