Microstructure stability and micro-mechanical behavior of as-cast gamma-TiAl alloy during high-temperature low cycle fatigue. (15th February 2018)

• Record Type: Journal Article
• Authors: Ding, Jie; Zhang, Minghe; Ye, Teng; Liang, Yongfeng; Ren, Yang; Dong, Chengli; Lin, Junpin
• Is Part Of: Acta materialia. Volume 145(2018)
• Page Start: 504
• Page End: 515
• Publication Date: 2018-02-15
• Subjects: High Nb-containing TiAl alloys -- Low cycle fatigue -- High-energy X-ray diffraction -- Phase transformation; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2017.12.040
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: This study systematically investigated the low cycle fatigue deformation of a high Nb-containing TiAl alloy with a nominal chemical composition of Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y at 850 °C by using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and synchrotron-based high-energy X-ray diffraction (HE-XRD) techniques. Cyclic stress-strain (CSS) behavior, lattice strain, and peak broadening of {100}α2, {201}γ, and {202}ωo planes, phase transformations, and crack propagation behavior were obtained for samples with three total strain amplitudes: Δ ε t /2 = ±0.25%, Δ ε t /2 = ±0.28%, and Δ ε t /2 = ±0.30%. At early deformation stages, α2lamellae transformed into ωo phase with a distinct orientation relationship, and a certain orientation relationship (OR) between them was observed after the following cyclic deformation. Furthermore, γ particles precipitated within the single ωo area. In addition, according to the peak intensity and peak broadening results, the ωo → B2 phase transformation occurred, leading to the appearance of single B2-phase areas. The lattice strains in the ωo phase were always in tension during the cyclic deformation and large differences of the lattice strains were found in the γ phase and α2 phase, not only the values but also the directions, which resulted in crack nucleated at and propagated along the α2 /γ lamellar interface. This study provides a better understanding of the low cycle fatigue deformation of TiAl alloys. Graphical abstract: Image 1