Solid-State Additive Manufacturing of Aluminum-Cerium Alloys for Aerospace Structural Applications

Additive manufacturing (AM) has completely altered the traditional component manufacturing and qualification paradigm. It provides unitization and topological optimization opportunities simultaneously. Broadly, the additive manufacturing processes are classified as fusion based or solid state. The solid state additive manufacturing processes are relatively nascent. Among these, friction stir based process such as AFSD involves intense shear deformation of material while building. These friction stir welding (FSW) derived techniques have ability to produce microstructures that lead to better mechanical properties than the conventionally processed parent alloys; in many cases overcoming the traditional strength-ductility tradeoff paradigm. The best way to capture this advantage is to conduct materials selection for build which benefit from the attributes of these processes. Recent exploration on the addition of 6-16 wt% Ce exhibited exceptional improvement in high temperature properties in addition to better thermal stability and castability. Ability to achieve such unprecedented properties in as-cast condition avoids the need for any further post heat treatment, thereby reduces the overall manufacturing cost as well as time. Al-Ce alloys were shown to exhibit almost 60% YS and 45% UTS retention at 300°C compared to room temperature. Additionally, addition of alloying elements such as Si and/or Mg also improved the thermal properties of the Al-Ce alloy compared to other commercial cast alloys. Excellent high temperature properties, castability, and thermal stability of Al alloys with Ce addition enables Al-Ce-XX-YY alloy system as an excellent candidate to explore for AFSD. Initial results on AFSD of Al-Ce alloys show significant microstructural refinement and balance of mechanical properties. These results will be presented along with a comparison with a number of leading aerospace aluminum alloys.