Atomic-level crystallization in selective laser melting Zr-based metallic glass
As a promising additive manufacturing technique, selective laser melting (SLM) provides the probability for fabricating metallic glassy components free of the constraints of geometrical complexity and dimensions. However, unexpected crystallization greatly affects the microstructure and degrades mechanical performance of SLM-fabricated metallic glasses (MGs). To clarify the crystallization mechanism and the effect of laser processing on the formation of crystallization, we investigate the atomic-level crystallization in SLM Zr90Cu10 MG by molecular dynamics simulations. Result shows a highly related crystallization with laser scan speed lies in atomic-level cluster changes. Lower scan speed leads to dramatically increased fraction of BCC crystal phase, accompanied with the nucleation of few HCP and FCC crystal phases. As scan speed increases, more icosahedron-like clusters are formed, leading to the formation of MG, while the nucleation of crystal phase is suppressed. The suppression of crystallization is further attributed to higher average temperature variation rate induced by higher scan speed, which reduces the relaxation time, preventing the nucleation and growth of crystal phases. This work contributes to the understanding of the crystallization in MG during SLM process at atomic level, providing a guidance to suppress the crystallization in the SLM of desired metallic glassy components.