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 fee 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 Hv. The sheet showed age hardening, and the peak hardness of 340 Hv was obtained after aging at 623 K for 900 s, in which ultrafine coherent precipitates of L12 Al3Ti phase were uniformly dispersed. As the annealing temperature increased up to 773 K, large D022 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 L12 phase probably due to the effect of oxygen.