Age Hardening of Ultrafine Grained Al-Ti-Cr Alloys Fabricated by Continuous Electron Beam Evaporation

Abstract

Supersaturated Al-Ti-Cr alloys were produced by a continuous electron beam evaporation technique. The as-deposited alloy sheets were fcc supersaturated solid solution with an average grain size of about 400 nm. Due to the fine grain size, the hardness of the alloy was as high as 270 H v . The sheet showed age hardening, and the peak hardness of 340 H v was obtained after aging at 623 K for 900 s, in which ultrafine coherent precipitates of L1 2 Al 3 Ti phase were uniformly dispersed. As the annealing temperature increased up to 773 K, large D0 22 particles precipitate by the discontinuous precipitation mode and the hardness significantly decreased. Although Cr was confirmed to be enriched in the L1 2 particles, it did not completely stabilize the L1 2 phase probably due to the effect of oxygen.