CALPHAD-guided design and experimental study on a novel Al-Ti-Nb alloy

CALPHAD-guided design methodology was used to develop a novel lightweight Al-Ti-Nb alloy with nearly 50% in-situ formed trialuminide reinforcement. After compositional optimization, we selected Al87.5Ti6.25Nb6.25 (at.%) as the experimental alloy composition and subjected it to a 24-hour homogenization heat treatment at 475°C for attainment of equilibrium, guided by DSC and CALPHAD-derived melting point data. Phase and microstructure analysis revealed a microstructure with approximately 50% volume of an FCC Al-rich matrix and 50% trialuminide phases for strengthening. The experimental onset melting point of the Al-rich matrix was determined to be 647°C, significantly surpassing Al-Si based high-temperature alloys (577 ℃), showcasing the potential of this alloy as a high-temperature structural material. Nanoindentation tests demonstrated exceptional mechanical properties, with a microhardness of 3350 MPa that not only outperformed 7075 Al alloy, A390 Al-Si alloy, and commercially pure Ti but also exceeds the levels of Ti-6Al-4V alloy at nearly 28% lower density. The study's significance lies in its integration of CALPHAD predictions and meticulous microstructural investigation, offering an effective approach for the design and characterization of novel Al-based alloys.