Microstructure and properties of additively manufactured Al-Ce-Mg alloys

Additive manufacturing of aluminum alloys is largely dominated by a near-eutectic Al-Si compositions, which are highly weldable, but have mechanical properties that are not competitive with conventional wrought Al alloys. In addition, there is a need for new Al alloys with improved high temperature properties and thermal stability for applications in the automotive and aerospace fields. In this work, we considered laser powder bed fusion additive manufacturing of two alloys in the Al-Ce-Mg system, designed as near-eutectic (Al-11Ce-7Mg) and hyper-eutectic (Al-15Ce-9Mg) compositions with respect to the binary L -> Al+Al11Ce eutectic reaction. The addition of magnesium is used to promote solid solution strengthening. A custom laser scan pattern was used to reduce the formation of keyhole porosity, which was caused by excessive vaporization due to the high vapor pressure of magnesium. The microstructure and tensile mechanical properties of the alloys were characterized in the as-fabricated condition and following hot isostatic pressing. The two alloys exhibit significant variations in solidification structure morphology. These variations in non-equilibrium solidification structure were rationalized using a combination of thermodynamic and thermal modeling. Both alloys showed higher yield strength than AM Al-10Si-Mg for temperatures up to 350 degrees C and better strength retention at elevated temperatures than additively manufactured Scalmaloy.

Automated summary

Additive manufacturing of aluminum alloys is often dominated by near-eutectic Al-Si compositions, but there is a demand for new alloys with improved high temperature properties. This study focused on laser powder bed fusion additive manufacturing of two alloys in the Al-Ce-Mg system, utilizing a custom laser scan pattern to reduce porosity formation. Variations in solidification structure morphology were observed and explained using thermodynamic and thermal modeling.