Formation of a bimodal structure in ultrafine Ti–Fe–Nb alloys with high-strength and enhanced ductility

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 609; pp. 60 - 64
• Main Authors: Cao, G.H., Peng, Y.F., Liu, N., Li, X., Lei, Z.S., Ren, Z.M., Gerthsen, D., Russell, A.M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.07.2014; Elsevier
• Subjects: Alloys; Applied sciences; Compressive strength; Cross-disciplinary physics: materials science; rheology; Deformation, plasticity, and creep; Elasticity. Plasticity; Electron microscopy; Eutectics; Exact sciences and technology; Intermetallics; Iron compounds; MATERIALS SCIENCE; Mechanical characterization; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Nanoscale materials and structures: fabrication and characterization; Nanostructured materials; Niobium; Niobium base alloys; Other topics in nanoscale materials and structures; Physics; Plasticity; Titanium alloys; Titanium base alloys; Titanium compounds; Treatment of materials and its effects on microstructure and properties; Titanium alloys; Mechanical characterization; Electron microscopy; Nanostructured materials; Eutectics; Plasticity; Levitation melting; Ultimate strength method; Ductility; Compressive strength; Plastic deformation; Dual phase structure; Lamellar structure; Eutectic; Mismatch lattice; Titanium alloy; Eutectic alloy; Mechanical properties; Compression test; Crucible; Dendrite; Orientation relation; Mechanical test; Compressive stress; Niobium addition; Interface
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2014.04.088

Bulk (Ti70.5Fe29.5)100−xNbx (x=0, 3, 5 and 7at%) alloys were prepared by cold crucible levitation melting, and their mechanical properties were tested in compression at room temperature. A (Ti70.5Fe29.5)97Nb3 alloy specimen in compression exhibited an ultimate compressive strength of 2.53GPa and a compressive plastic strain of 15%. Electron microscope observations indicated that lamellar structures present in the eutectic Ti70.5Fe29.5 alloy could be modified by the addition of Nb to obtain a bimodal structure. The improvement of the mechanical properties is attributed to two factors: (1) the bimodal phase size distribution with micrometer-sized primary β-Ti dendrites embedded inside a matrix of refined ultrafine eutectics (β-Ti+TiFe), and (2) the larger lattice mismatches between the β-Ti and TiFe phases in Nb-modified eutectic Ti–Fe alloys that introduce coherency strain at the interface. The orientation relationship of A2 β-Ti with B2 TiFe in binary and Nb-modified Ti–Fe alloys is TiFe (110)[001] || β-Ti (110)[001].