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

• We proposed a re-scan strategy to prevent crack propagation in SLM.
• The re-scan should be carried out at a low laser energy density.
• The underlying mechanism is through reduction and relief of residual stresses.
• Lowered temperature gradient and superplasticity account for reduction of stress.
• For the first time, a crack-free BMGCs gear with a large size was produced.

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 Al85Ni5Y6Co2Fe2 bulk 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 ∼25 mm and height ∼10 mm.