Effects of Gd addition, lamellar spacing and loading direction on creep behaviour of a fully lamellar Ti-44Al-1Mn-2.5Nb alloy

Abstract

A quaternary Ti-44Al-1Mn-2.5Nb (at.%) alloy and an equivalent alloy with 0.15 at.% rare earth element Gd (Ti-44Al-1Mn-2.5Nb-0.15Gd) were prepared by arc melting and casting. Both alloys were heat treated to obtain a fully lamellar microstructure with an average grain size of ∼270 μm. A controlled furnace cooling gave rise to an average lamellar spacing of the order of ∼250 nm whereas a fast cooling in air was used to produce much finer lamellar spacings of the order of ∼25 nm in both alloys. Tensile creep tests showed that for the materials with similar lamellar spacings, the secondary creep rate of the Gd-containing alloy was lower than that of the quaternary alloy, and for the same alloys,..