Nanometer-scale, fully lamellar microstructure in an aged TiAl-based alloy

This article reports on the optical microscopy, transmission electron microscopy, and hardness experiments conducted on a Ti-45Al-2Cr-Nb alloy that was aged between 400 degrees C and 800 degrees C. The aging treatment was conducted on specimens that were quenched to retain the high-temperature alpha/alpha 2 structure. The aging treatment produced an ultrafine, nanometer-scale, fully lamellar microstructure, ranging from 8 nm in thickness at 600 degrees C to 17 nm at 700 degrees C. The fine lamellar microstructure produced a large strengthening effect, raising the hardness to 540 on the Vickers scale. The lamellar structure nucleates preferentially at grain boundaries and grows into the grain interior.