Superplasticity of nanostructured Ti-6Al-7Nb alloy with equiaxed and lamellar initial microstructures processed by High-Pressure Torsion

7th International Conference on Nanomaterials by Severe Plastic Deformation

Cubero-Sesin, Jorge M.^1,2 ; Gonzalez-Hernandez, Joaquin E.^1 ; Ulate-Kolitsky, Elena^1 ; Edalati, Kaveh^3,4 ; Horita, Zenji^3,4

Escuela de Ciencia e Ingeniería de Los Materiales, Instituto Tecnológico de Costa Rica, Cartago

159-7050, Costa Rica^1

Centro de Investigación en Ciencia e Ingeniería de Los Materiales, Instituto Tecnológico de Costa Rica, Cartago

159-7050, Costa Rica^2

Department of Materials Science and Engineering, Kyushu University, Fukuoka

819-0395, Japan^3

WPI, International Institute of Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka

819-0395, Japan^4

关键词: Elongation to failure;    High pressure torsions;    High temperature tensile tests;    Initial microstructures;    Micro-structure evolutions;    Microstructural modification;    Ti-6Al-7Nb alloys;    Titanium aluminum;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/194/1/012041/pdf
DOI  :  10.1088/1757-899X/194/1/012041

来源: IOP

【 摘 要 】

Microstructural modifications of a biomedical Ti-6Al-7Nb alloy were accomplished via heat treatment in 3 different quenching mediums and then processed by High-Pressure Torsion (HPT) at room temperature. The microstructure of the as-received condition is composed of an equiaxed duplex (α+β) structure. After the heat treatment, a combination of primary α phase and lamellar structures was obtained with an increasing fraction of the martensitic lamellar with increasing cooling rate. After HPT processing, refinement of the microstructures was observed for N=5 revolutions. Transmission electron microscopy (TEM) of the sample quenched in liquid nitrogen confirmed the nanostructure with grain sizes below 100 nm and high density of lattice defects after HPT processing for N=5 revolutions. High-temperature tensile tests were carried out at 800 °C with an initial strain rate of 2×10-3s-1on specimens with different combinations of heat treatment and HPT straining. The test in the as-received condition presented a maximum elongation to failure of ∼400% after HPT processing for N=5 revolutions. The highest elongation to failure in the heat-treated samples was ∼580% in the sample quenched in liquid nitrogen and processed for N=5 revolutions.