Research Projects

2XXX series aluminum alloys are extensively used in aerospace fuselage structures, missile fuel tanks, and lightweight vehicles due to their excellent cryogenic strength and moderate performance at elevated temperatures. However, their application is limited to temperatures below 150 °C, primarily due to rapid coarsening of strengthening phases such as θ′ (Al₂Cu), which compromises mechanical stability. As a result, these alloys are mainly restricted to subsonic aircraft. Enhancing their strength retention at higher temperatures could significantly expand their utility in advanced aerospace systems, including supersonic aircraft and fighter jets. Recent research has focused on improving the high-temperature performance of 2XXX alloys through the addition of L1₂-ordered phase-forming elements such as Zr, Sc, and Ti. These elements promote the formation of coherent Al₃X-type (X = Zr, Sc, etc.) precipitates, which exhibit excellent thermal stability and hinder dislocation movement at elevated temperatures. However, the low solubility and limited volume fraction of these precipitates restrict their overall strengthening contribution. Parallel efforts involving the addition of cerium (Ce) through additive manufacturing (AM) techniques have shown promise in forming thermally stable Al-Ce intermetallics, but the complexity and cost of AM processes hinder widespread application. In this project, we propose to combine the benefits of both approaches by developing a Ce-containing Al-4.5Cu alloy system capable of forming thermally stable intermetallic phases and micro addition of L1₂-forming elements by incorporating precipitates or dispersoids through conventional processing. Ce additions are expected to promote the formation of Al₁₁Ce₃ or related phases with high coarsening resistance, while microalloying with L1₂-forming elements (e.g., Sc and Er) can enhance thermal stability via coherent precipitate strengthening. This dual-precipitation strategy aims to deliver improved strength at room temperature and above 300 °C. The alloy will be synthesized by Direct Chilled casting process. Subsequent heat treatments will include solutionizing and quenching, followed by a two-stage aging process: 1st step ageing at 300–400 °C to promote formation of thermally stable precipitates/dispersoids, and a 2nd step ageing at 200 °C to facilitate θ″/θ′ precipitation. Microstructural evolution will be studied using optical microscopy, SEM, EBSD, and TEM, with a focus on characterizing L1₂ precipitates, Ce-containing intermetallic, and θ″/θ′ phase distribution. Mechanical properties will be evaluated by hardness measurements and tensile testing, and thermal stability will be assessed through isothermal aging and coarsening kinetics analysis.