Abnormal grain growth in randomly-oriented fine grains in an Al–Mg–Sc–Zr alloy processed by laser-powder-bed-fusion

Abstract

In this work, we report a counter-intuitive activation of abnormal grain growth (AGG) in randomly-oriented fine grains (FGs) in an L-PBF Al–Mg–Sc–Zr alloy, which is unlikely from perspectives of curvature-driven grain growth, crystallographic texture or strain-induced boundary migration. The observed spontaneous AGG is understood in light of the growth instability of an arbitrary grain in an evolving particle-pinned polycrystalline aggregation. A generalized criterion for AGG is hence proposed, which efficaciously explains the observed susceptibility of FGs to AGG, the presence of multiple AGG activation sites, and the asynchrony of AGG activation.

Keywords

• Additive manufacturing
• Al–Mg–Sc–Zr alloy
• abnormal grain growth
• Zener pinning