Microstructure and Properties of Additively Manufactured Al-Ce-Mg Alloys

Abstract

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°C and better strength retention at elevated temperatures than additively manufactured Scalmaloy.

High Strength Aluminum Additive Manufacturing

“…In response to these opportunities, ORNL has investigated a variety of Ce containing Al alloys for additive manufacturing. Al-Ce-Mg [11] showed excellent strength, but suffered from challenges in processing due to the high vapor pressure of Mg, leading to increased vaporization and propensity for keyhole formation and changes in alloy composition. Al-Ce-Mn alloys [12,13] exhibit stability in mechanical properties at high temperatures, but have low ductility due to extremely high intermetallic phase content.…”