Abstract
Selective laser melting(SLM)has attracted great attention in the fabrication of magnesium-based biodegradable implants.However,current SLMed magnesium alloys are generally suffered from rapid corrosion,which is deadly detrimental to their use.Herein,we thoroughly revealed why they are so vulnerable to corrosion through a typical SLMed AZ91D material model.An abnormally spatiotempo-ral"bulk erosion"mechanism was found,not the well-known"surface corrosion"mode of traditionally plastic-deformed alloys.The unique microstructure derived from SLM possesses high chemical reactivity,which is favorable for interactional attacks of fast fluid penetration,severe local corrosion and intensive micro-galvanic corrosion.Thus,it brings two orders of magnitude in corrosion rates compared with its plastic-deformed counterparts.In vitro,such fast-corrosion induced apparent cytotoxicity,cell damage,and further apoptosis to rat and mouse derived mesenchymal stem cells.In vivo,the material disinte-grates into small pieces in a short period,and results in unexpected bone destruction and long-lasting foreign body reactions in Sprague Dawley rats.Close attention should be paid to this issue before SLMed Mg-based implants being applied in patients.
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