Laser additive manufacturing of Zn metal parts for biodegradable applications: Processing, formation quality and mechanical properties

Zn based metals have exhibited promising applications for biodegradable implants. Only a handful of very recent reports were found on additive manufacturing of Zn metal by selective laser melting (SLM). This work provided a systematic study on densification, surface roughness and mechanical properties regarding SLM of Zn metal. Single track surface after laser melting was rugged and twisted with a large amount of attached particles due to severe Zn evaporation. For SLM produced solid parts, the relative density was more than 99.50%; the surface roughness Sa was 9.15–10.79 μm for as-melted status and 4.83 μm after sandblasting, both comparable to optimal results obtained by SLM of common metals. The microstructure was made up of fine columnar grains. The average values of hardness, elastic modulus, yield strength, ultimate strength and elongation were 42 HV, 23GPa, 114 MPa, 134 MPa, and 10.1% respectively, better than those obtained by most manufacturing methods. The superior mechanical properties were attributed to high densification and fine grains resulted by optimal processing control of Zn evaporation and laser energy input. Cardiovascular stents were printed out to demonstrate additive manufacturing ability for complicated structures. All the results indicate the encouraging prospect of additive manufacturing of Zn based metals for biodegradable applications.