A comparative study of iron, cobalt or cerium micro-alloying on microstructure and apparent viscosity of Al-5Ni alloy

Abstract

The micro-alloying is promising in improving the mechanical properties, thermal conductivity, and castability of the near-eutectic Al-Ni alloys, enabling them to be formed via the special casting or additive manufacturing technique. But the rheological behavior of the molten near-eutectic Al-Ni alloys is not clear. The present work investigates the effect of three kinds of micro-alloying agents (iron, cobalt, and cerium) at 0.3 wt% on the solidification and rheological behaviors of the Al-5Ni alloy. Results indicate that the addition of the micro-alloying element can significantly refine the α-Al grains in the Al-5Ni alloy, leading to the improvement of the thermal conductivity and mechanical properties. The cooling curves thermal analysis suggests that the incorporated micro-alloying element can notably change the cooling rate of the melts during the solidification course. Phase-field simulations illustrate that the different cooling rates cause the change of the shape factor and the fraction of α-Al grains during the solidification course of the alloy, leading to the remarkable difference of the viscosities at different temperatures and shear rates of the Al-5Ni melts. This work provides an in-depth understanding of the correlation between the solidification route and rheological behavior of the Al-5Ni melts with micro-alloying treatment.