Suppression of hot cracking in additively manufactured Mg-Zn alloys via CaO nanoparticle addition

This study investigated the effect of CaO nanoparticles on hot cracking in additively manufactured Mg-Zn alloys. Mg-5Zn and Mg-5Zn-1.5CaO alloys were fabricated via selective laser melting (SLM). During SLM, CaO underwent a reduction reaction, where the released Ca probably interacted with the melt and altered the solidification path by consuming Zn. This process narrowed the solidification temperature range of the Mg-5Zn alloy, leading to a 64% reduction in the average solidification crack width. Under optimal SLM parameters (70 W laser power, 400 mm/s scanning speed), the Mg-5Zn-1.5CaO achieved a microhardness of 68.7 HV and an increase in relative density from 90.3% to 92.3%, compared to the Mg-5Zn alloy. The results demonstrate that the addition of CaO nanoparticles is an effective approach for suppressing hot cracking and improving the density of SLMed Mg-Zn alloys by regulating solidification behavior.