摘要
Diffusion coefficient decides the solute diffusion length and is a critical parameter in the selection of microstructare scales and in governing microstructure transitions. Al-25 wt%Sm alloy is selected to reveal the impact of low diffusion coefficient on the eutectic instability, and the results are compared with those of Al-Cu alloys. Laser remelting experiments are performed and the transition growth velocity from euteetic to α-Al dendrite is examined. Compared with Al-Cu alloys, the eutectic instability takes place at a velocity more than one order of magnitude smaller. The theoretical calculation by the Trivedi-Magnin-Kurz （TMK） model also predicts that the eutectic will become instable at smaller growth velocity for Al-Sm alloy than Al-Cu alloy, which is ascribed to the low diffusion coefficient.
Diffusion coefficient decides the solute diffusion length and is a critical parameter in the selection of microstructare scales and in governing microstructure transitions. Al-25 wt%Sm alloy is selected to reveal the impact of low diffusion coefficient on the eutectic instability, and the results are compared with those of Al-Cu alloys. Laser remelting experiments are performed and the transition growth velocity from euteetic to α-Al dendrite is examined. Compared with Al-Cu alloys, the eutectic instability takes place at a velocity more than one order of magnitude smaller. The theoretical calculation by the Trivedi-Magnin-Kurz （TMK） model also predicts that the eutectic will become instable at smaller growth velocity for Al-Sm alloy than Al-Cu alloy, which is ascribed to the low diffusion coefficient.
