Selective laser melting of hypereutectic Al-Si40-powder using ultra-short laser pulses

We investigate the use of ultra-short laser pulses for the selective melting of Al-Si40-powder to fabricate complex light-weight structures with wall sizes below 100mm combined with higher tensile strength and lower thermal expansion coefficient in comparison to standard Al-Si alloys. During the cooling process using conventional techniques, large primary silicon particles are formed which impairs the mechanical and thermal properties. We demonstrate that these limitations can be overcome using ultra-short laser pulses enabling the rapid heating and cooling in a non-thermal equilibrium process. We analyze the morphology characteristics and micro-structures of single tracks and thin-walled structures depending on pulse energy, repetition rate and scanning velocity utilizing pulses with a duration of 500fs at a wavelength of 1030nm. The possibility to specifically change and optimize the microstructure is shown.