Wettability And Control Mechanism Of Aluminum-based Material Fabricated By Selective Laser Melting

In this paper,Al-12Si was used as the original powder to form single tracks and samples.The control of the wettability of Al-12Si by different processing parameters and the mechanism of internal microstructure and mechanical properties of the material were studied.The effect of surface morphology of the substrate on the spreading of powder and forming of single track during SLM processing was studied.The results show that the morphologies of single tracks changed with roughness of the top surface?Top Ra?of SLM parts.By analyzing the variation of wetting angles on the surface processed previously as well as the dimensions of each single track,different wettability and flow behavior of the molten metal under various solidification environments of the single track during SLM were revealed.By studying the Al-12Si samples formed by different laser processing parameters,the influence of scanning speed on the wettability of molten metal was discussed in detail,which affected the forming quality of samples.When the scanning speed was too low,the laser energy density was too high,resulting in over-burning and coarsening microstructure.When scanning speed was too high,the metal powder melted insufficiently,so poor wettability was obtained.It was found that when the laser power was 370W and scanning speed was 1750 mm/s,metal powder fully melted,thus improving the wettability and stability of molten pool.The interlayer bonding was good and mechanical property was excellent.The microhardness reached the maximum value(127.5 HV_0.1).Meanwhile,the best wear resistance was obtained.TEM analysis of the sample revealed that Al,Si and Mg₂Si existed at the grain boundaries,and MgAl₂O₄ existed in the intragranular region.The influence of laser beam incident angle on the forming quality of Al-12Si samples fabricated under optimal processing parameter was investigated.As laser irradiation angle increased,the spot shape changed from a small and gathered circular shape to an elliptical shape,thus decreasing energy density.The metal powder was in unmolten or semi-molten state,so the wettability weakened.The relative density,microstructure and tensile strength of samples became poorer.It was found that when the laser beam was vertically irradiated,the spot diameter was small,and laser energy was concentrated,thus sufficiently melting powder and improving wetting behavior.The narrow and deep molten pool formed in the sample.The interlayer bonding was good,so the highest density of 98.2%was obtained.The tensile strength was up to 440.07 MPa.