THE EFFECT OF HETEROGENEOUSSTRUCTURE ON MECHANICALPROPERTIES OF β -SOLIDIFIED γ -TIALBASED ALLOY

The paper presents a comparative study of the mechanical properties of the alloy states based on gamma titanium aluminide Ti-44.0Al-2.0Cr-1.8Nb-1.65V-0.1Gd with a lamellar and heterogeneous structure. The lamellar structure is represented by colonies with a size of D = 50 μm and an interlamellar distance of λ = 200 nm. The heterogeneous structure is formed during the cellular reaction and is represented by nanolamellar (α2 + γ)-colonies (D = 20 μm, λ = 100 nm), as well as coarse lamellar (β + γ)-colonies (D = 25 μm, λ = 1500 nm). The ratio of the proportions of nano- and coarse lamellar colonies was 50/50, while 20 vol.% of the structure is represented by particles of γ- and interlayers of β-phases. Mechanical test results showed an increase in elongation from 1.5% to 4.5%, and in ultimate tensile strength from 550 to 780 MPa upon transition from a lamellar to a heterogeneous structure. This increase in mechanical properties is due to the development of twinning in coarse lamellar (β+γ) colonies and the manifestation of the TWIP effect, as well as the activation of dislocation slip in nanolamellar (α2+γ) colonies by reverse stresses.