The role of a low-energy-density re-scan in fabricating crack-free Al₈₅Ni₅Y₆Co₂Fe₂ bulk metallic glass composites via selective laser melting

In this paper, we have investigated the use of a re-scanning strategy to prevent propagation of macro-cracks during the selective laser melting of an Al₈₅Ni₅Y₆Co₂Fe₂bulk metallic glass composites (BMGCs). These cracks form as a result of the high residual stress caused by the rapid heating and cooling of the material by the laser beam. Unlike crystalline materials, the BMGCs possess a supercooled liquid region in which the residual stress can be relieved by plastic flow. We show that by using a high power initial scan (designed to melt the material) followed by a lower power re-scan (for stress relief) cracking can be prevented. Using this approach, crack-free Al₈₅Ni₅Y₆Co₂Fe₂ BMGCs components have been fabricated, including a gear with a diameter ~25mm and height ~10mm.