Effect of laser processing parameters on porosity, microstructure and mechanical properties of porous Mg-Ca alloys produced by laser additive manufacturing

Laser additive manufacturing (LAM) was used to fabricate porous Mg-Ca alloys and the effect of laser processing parameters on porosity, surface morphology, microstructure, microhardness and compression performance were investigated. The results indicate that the porosity and surface morphology of the LAMed samples depend on the laser energy input. When energy density is between 875 J/mm3 and 1000 J/mm3, the porosity of porous magnesium alloy is between 18.48% and 24.60%, and at this time, the samples with better surface quality can be obtained. The LAMed porous Mg-Ca alloy shows overlapped cladding lines and periodic morphological features. With the farther away from the molten pool, the grains show a transition from equiaxed crystal to columnar crystal and the grain size increases. All the LAMed samples only consist of α-Mg phase and a lesser degree of MgO phase. The microhardness of LAMed samples is between 60 HV and 68 HV and the microhardness is superior to that of as-cast pure magnesium, which is mainly attributed to the grain refinement and solid solution strengthening. As laser energy input increases, the porosity decreases and the compression performance enhances meanwhile. The LAMed porous Mg-Ca alloy is a promising biodegradable material for future clinical application.