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Herein, a novel core-shell structured TiAl composite consisting of nanoparticles "shell" and a near fully lamellar "core" was designed using a Ti–48Al–2Nb–2Cr alloy and Boron nitride nanoplates. By tailoring microstructure and nanoparticles strengthening, the TiAl composite exhibited a superior combination of strength and ductility at high temperature, which achieved an ultimate tensile strength of 514.2 MPa and an outstanding fracture strain of 18.8 % at 850 °C. [ABSTRACT FROM AUTHOR]

Al x Nb 0.5 TiV 2 Zr 0.5 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) refractory high entropy alloys were prepared by vacuum arc melting to obtain a lightweight REHA with excellent microstructure and mechanical properties. The microstructure, density, hardness, and compressive properties at room and elevated temperatures of Al x Nb 0.5 TiV 2 Zr 0.5 alloys were investigated. All Al x Nb 0.5 TiV 2 Zr 0.5 alloys are composed of the BCC phase and the C14-Laves phase, and the volume fraction of the Laves phase raises from 12.03% to 22.83% and then decreases slightly to 20.31% with the increase of Al content. The density of Al x Nb 0.5 TiV 2 Zr 0.5 alloys decreases with the increase of Al content from 6.12 g/cm3 to 5.43 g/cm3, and the microhardness increases from 397.2 HV to 641.9 HV. At room temperature, the yield strength of Al x Nb 0.5 TiV 2 Zr 0.5 alloys increases obviously at first and then decreases slightly with the range of 843 MPa–1727 MPa. The compressive strain of the alloys obviously decreases from 33.4% to 13.7% at first and then increases to 16.6%. Upon increasing the temperature to 873 and 1073 K, the strength of all alloys decreases, and the yield strength of the Al0.8 alloy remains 1569 and 1108 MPa, respectively. The compression ratios of all Al x Nb 0.5 TiV 2 Zr 0.5 alloys reach 50% without fracture at this temperature. The specific yield strength of Al0.8 alloy acheives 312 × 103, 284 × 103, and 199 × 103 MPa·cm3g-1 at 298, 873, and 1073 K, which is superior to that of other alloys. A strong correlation between the mechanical properties and the Al content of Al x Nb 0.5 TiV 2 Zr 0.5 alloys is observed. Al is one of the elements that can promote the formation of the Laves phase, and the volume fraction of the Laves phase increases with the increasing Al content. As a hard intermetallic compound phase, the mechanical properties of the alloys are improved with the increasing volume fraction of the Laves phase. • The density of lightweight Al x Nb 0.5 TiV 2 Zr 0.5 alloys is between 6.12 g/cm3 and 5.43 g/cm3. • The Al x Nb 0.5 TiV 2 Zr 0.5 alloys show high hardness between 397.2 HV and 641.9 HV. • The Al0.8 alloy possesses high SYS at 298, 873, and 1073 K of 312, 284, and 199 MPa cm3g−1, respectively. • The strengthening mechanism of Al x Nb 0.5 TiV 2 Zr 0.5 alloys is mainly the second phase strengthening. [ABSTRACT FROM AUTHOR]

The tailoring of precipitates during hot deformation provides an opportunity to eliminate lengthy post-process heat treatment and removes the inherent disadvantages, such as abnormal grain growth. In this work, a novel short-process manufacturing method consisting of only pre-annealing and hot deformation steps was proposed for fabricating γ′-strengthened GH4720Li superalloy. Diverse nanoscale precipitation strengthening phases with bimodal distributions but similar matrix grain sizes were successfully modulated by this integrated two-step manufacturing method. The modulated superalloys fabricated under low deformation resistance and without typical long-time aging treatment exhibited high yield strength (∼1196 MPa) and ultimate tensile strength (∼1561 MPa) while maintaining a decent uniform elongation (∼19%) during tensile tests at room temperature. The dominant tertiary γ′ strengthening precipitates originate from the supersaturated matrix and dynamic evolution of secondary γ′ precipitates during hot deformation. In addition, the shearing of secondary γ′ through dislocation pairs promotes their dissolution during hot deformation. This study provides a novel pathway for the integrated short-process manufacturing of multimodal γ′ nickel-based superalloys and a new understanding for dynamically modifying the microstructure of precipitate-containing alloys during hot deformation. [ABSTRACT FROM AUTHOR]