Influence of minor cerium addition on microstructure and fluidity of as-cast Al-Cu-Mn-Mg alloy

Abstract

Al-Cu-Mn alloys are widely used to produce automobile components like cylinder heads and engine blocks because of their capability to retain excellent thermal and mechanical characteristics at high temperatures. However, the Al-Cu-Mn-based alloys demonstrate restricted fluidity, leading to casting defects such as shrinkage and incomplete filling. This research investigated the microstructure and fluidity of Al-4.7Cu-1.0Mn-0.5Mg (wt%) alloy with minor cerium (Ce) addition. The as-cast alloys predominantly comprise α-Al matrix, accompanied by the presence of Al₂Cu, Al₆Mn, and Al₈Cu₄Ce phases. The influence of adding Ce on the fluidity of the Al-4.7Cu-1.0Mn-0.5Mg alloy was investigated using a tri-spiral fluidity test mold in this research. The findings suggest that the addition of Ce within the range of 0.1 wt% to 0.5 wt% in the Al-4.7Cu-1.0Mn-0.5Mg alloy results in an enhancement in fluidity. Specifically, the alloy containing 0.4 wt% Ce exhibits a significant increase in fluidity distance, from 349.7 to 485.7 mm. This improvement can be attributed to the reduction in viscosity, the refinement of secondary dendrite arm spacing, and the modification of secondary phase particles. However, a higher concentration of Ce leads to a decrease in fluidity length, potentially due to the formation of Al₈Cu₄Ce.