Densification behavior of pure Zn metal parts produced by selective laser melting for manufacturing biodegradable implants

A lot of recent studies have shown that Zn based metals exhibit promising application prospects for biodegradable medical implants. Only a handful of recent reports can be found on additive manufacturing of Zn metal. Either the obtained density was quite low, or the process window was quite narrow due to severe evaporation. This paper aims to clarify the effect of processing parameters on densification behavior during selective laser melting (SLM) of pure Zn, and obtain high density in a reasonable process window. Single track melting and preliminary experiments were used to understand the process at first. Response surface methodology (RSM) was used to further investigate the effect of parameters on densification. A reasonable process window of high density over 99.90% was predicted and verified. Porosity was resulted by either lack of fusion due to insufficient laser energy or by gas entrapment due to excessive evaporation. For SLM parts of high density, the mechanical properties were measured as 46.31 ± 2.02HV, 20.47 ± 5.71 GPa, 122.13 ± 2.61 MPa, 137.9 ± 2.48 MPa and 8.13 ± 0.55% respectively for hardness, Young’s modulus, Yield strength, ultimate strength and elongation. The paper provided processing knowledge on SLM of Zn metal and solved the most difficulty dealing with laser melting of Zn metal: low densification, thus paved the way for additive manufacturing of Zn based metals for biodegradable implants.