Creep behaviour and mechanism in a fully lamellar Ti-44Al-1Mn-2.5Nb-0.15Gd alloy

Abstract

The creep behaviour and deformation mechanism in a Ti-44Al-1Mn-2.5Nb-0.15Gd (at%) were studied. The material had a fully lamellar structure with an average grain size of ∼265 μm and mostly alternating γ/α2 interfaces with an average lamellar spacing of ∼0.25 μm. Tested under constant stress and in vacuum the material exhibited the normal three stage creep with a well-defined steady state creep that lasted for 5-10% in many cases. Examination of the specimens deformed to different strains in the three stages by TEM revealed that the microstructures were significantly different in the soft and hard-oriented grains. The lattice dislocations in the soft γ lamellae increased in number and formed ..