Effect of interlamellar spacing on strength-ductility combination of β-solidified γ-TiAl based alloy with fully lamellar structure

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2023-01, Vol.862, p.144458, Article 144458
• Main Authors: Panov, D.O., Sokolovsky, V.S., Stepanov, N.D., Zherebtsov, S.V., Panin, P.V., Volokitina, E.I., Nochovnaya, N.A., Salishchev, G.A.
• Format: Article
• Language: English
• Subjects: Aging (metallurgy); Compression loads; Compressive strength; Crack initiation; Ductility; Edge dislocations; Elongation; Forging; Fracture mechanics; Gamma TiAl based Alloys; Interlamellar spacing; Intermetallic compounds; Intermetallics; Lamellar structure; Nucleation; Strain hardening; Strain localization; Strength-ductility combination; Titanium aluminides; Titanium base alloys; Ultimate tensile strength; Yield strength; Yield stress
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.144458

The paper reveals the possibility for obtaining excellent strength-ductility combination under both tension and compression in a fully lamellar β-solidified γ-TiAl based alloy by controlling the interlamellar spacing. Ingots of the alloy were subjected to multi-axial forging, quenching and further aging at 800–1050 °C to produce microstructures with the colony size of 25 μm and interlamellar spacing (λ) in the range from 10 to 1500 nm. A good balance between ductility and strength was found at λ ∼100 nm under both tension (elongation to fracture of 2.9%; ultimate strength - 875 MPa) and compression (peak strain and stress of 39% and 2700 MPa, respectively) due to a strain transfer by transverse twin/slip bands that improved strain hardening capacity. Both coarser and thinner lamellae caused pronounced strain localization and early crack nucleation resulting in failure. Meanwhile, the Hall-Petch relationship was observed between the yield strength and interlamellar spacing above λ ∼20–50 nm. At a lower interlamellar spacing the yield strength stabilized at the values of 820 and 1150 MPa upon tensile and compression loading, respectively. The dependences of deformation and fracture mechanisms on the interlamellar spacing and loading scheme are discussed. •Interlamellar spacing (λ) of Ti-43.2Al-1.9V-1.1Nb-1.0Zr-0.2Gd-0.2B alloy varies from 10 to 1500 nm.•Tensile-compression asymmetry is derived.•Maximum of ductility and ultimate strength is observed at λ∼100 nm under both tension and compression.•Yield strength and interlamellar spacing obey to the Hall-Petch relationship above the critical interlamellar spacing.•Yield strength stabilized below the critical interlamellar spacing.