Effect of adding Pr on the microstructure and hot tearing sensitivity of as-cast Al-Cu-Mg alloys

In this study, the effect of Pr on the microstructure and hot tearing sensitivity of the Al-4.4Cu-1.5Mg-0.15Zr alloy was studied using a self-made multi-channel “cross” hot tearing test device. With the increase in Pr content from 0 to 0.5 wt%, the average grain size, modified hot tearing sensitivity (HTS 1 ), and cracking susceptibility coefficient (CSC) of the alloy initially decreased and subsequently increased. Similarly, the range of the solidification temperature exhibited a small decrease. In contrast to the alloy without Pr, the average grain size decreased from 167.0 to 81.5 μm; the range of the solidification temperature decreased from 143.71 to 137.90 °C; the HTS 1 value of the alloy decreased from 228 to 60, and the CSC value decreased from 0.629 to 0.159 with the addition of 0.3 wt% Pr. The mechanism of reducing the hot tearing sensitivity of the alloy with the addition of Pr indicated that the microstructure was refined and the solidification temperature range was decreased. This was conducive to the increased formation of intergranular bridging at the grain boundary. Finally, the hot tearing sensitivity of the alloy was reduced. • The effect of trace addition of Pr (0–0.5 wt%) on the microstructure of Al-Cu-Mg alloy was studied. • The hot tearing sensitivity was studied by a self-made multi-channel “cross” hot tearing test device. • The hot tearing mechanism of alloy with addition of Pr was studied based on multi-theory.