Key Laboratory of Non ferrous Metallic Materials Science and Engineering

Changsha, China

Key Laboratory of Non ferrous Metallic Materials Science and Engineering

Changsha, China
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Wu D.,Central South University | Liu L.B.,Central South University | Liu L.B.,Key Laboratory of Non ferrous Metallic Materials Science and Engineering | Zhang L.G.,Central South University | And 3 more authors.
Journal of Materials Engineering and Performance | Year: 2017

A combinatorial approach has been applied to investigate the influence of Cr on the microstructure and properties of Ti6Al4VxCr alloys. A diffusion couple was manufactured with Ti6Al4V and Ti6Al4V20Cr alloys and annealed at 1000 °C for 600 h to obtain a wide range of compositions. It was heated to 1050 °C (above β transus) for 6 h, quenched to room temperature and subsequently aged at 600 °C for 6 h to achieve the typical α + β two-phase microstructures. Combining electron probe microanalysis, scanning electron microscope and nanoindentation, the relationships between the composition and microstructure as well as hardness of the diffusion couple were determined. By calculating the volume fractions using Thermo-Calc, it was found that after aging the Ti6Al4V6Cr sample contained a reasonable (~57 vol%) content of fine α phase and showed peak hardness among the Ti6Al4VxCr alloys. HAADF-STEM and XRD revealed that after solution treatment above the β transus temperature and quenching, the metastable α″ lamellar formed in the Ti6Al4V6Cr alloy. Subsequent isothermal aging of the α″ lamellar became coarse acting as precursors/preferential nucleation sites for the stable α phase. © 2017 ASM International


Wu D.,Central South University | Zhang L.,Central South University | Zhang L.,Key Laboratory of Non ferrous Metallic Materials Science and Engineering | Liu L.,Central South University | And 4 more authors.
International Journal of Materials Research | Year: 2017

A combinatorial approach has been applied to build the database of composition dependent microstructure and hardness of the Ti5553-Fe system. The relationship between the composition and microstructure as well as the hardness was obtained. (Ti5553)96-Fe4 was found to have almost the same hardness as that of Ti5553, but a relatively coarser intragranular a phase. High-angle annular dark field imaging revealed that Fe mainly concentrated in the β phase, which strengthened the b phase through solution strengthening. This means that (Ti5553)96-Fe4 may have the same strength as that of Ti5553 but higher fracture toughness. The formation of FeCr compound consumed the b stabilizer elements Fe and Cr, which led to unusual increasing of the nucleation rate and the volume fraction of a phase in (Ti5553)88-Fe12.

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