Effect of laser power on microstructure and mechanical properties of pure Zn fabricated via laser powder bed fusion

The preparation of biodegradable pure Zn porous scaffolds using additive manufacturing technology has great potential for application. However, the mechanical properties of pure Zn are not sufficient for the clinical application of stents. An object of this paper was to investigate the effect of laser power on microstructural evolution and tensile properties of pure Zn fabricated via laser powder bed fusion (LPBF). The results demonstrated that the temperature gradient and heat storage were the main factors determining the microstructure. The formation of columnar grains was due to the high temperature gradient in the early printing stage, and the equiaxed grains in the middle and top region were attributed to the heat storage induced recrystallization and columnar-to-equiaxed transition (CET), respectively. In addition, as the laser power increased from 40 W to 60 W, the recrystallization degree increased, and the Kernel average misorientation value and Taylor factor decreased gradually, resulting in a significant increase in the ductility. The mechanical properties were maximized at the laser power of 60 W and the scanning rate of 150 mm/s (yield strength, tensile strength and elongation of samples can reach 82.02 MPa, 116.20 MPa and 37.16 %, respectively). This work provides theoretical support for optimizing the mechanical properties of LPBF Zn-based materials by microstructural regulation.