Search

• The FeCrNi MEA exhibits outstanding corrosion resistance with a low corrosion current density and noble breakdown potential. • The Cr-rich passive film formed on the surface of the FeCrNi MEA has few defects and strongly self-healing ability. • The thick chromium oxide formed on the grain boundary reduces the erosion in this area. The corrosion behavior and mechanism of a novel FeCrNi medium entropy alloy (MEA) prepared by powder metallurgy method in 3.5 wt% NaCl solution was investigated in this study. The results indicated that, compared with the 316L SS, the FeCrNi MEA exhibits outstanding corrosion resistance with a more positive breakdown potential (0.982 V SCE) and lower current density (8.317 × 10 − 8 A / c m 2). The passive film formed on the surface of the FeCrNi MEA is a Cr-riched and less defective film. At the same time, it also has a strong self-healing ability. Uniform microstructure and high Cr content are responsible for the good anti-corrosion performance. [ABSTRACT FROM AUTHOR]

• A novel precipitation strengthened FeCoNi MEA were synthesized through powder metallurgy method. • This Al6Ti7 MEA exhibits a high yield strength (796 MPa) with moderate ductility retention (20.3%). • The high strength is mainly attributed to the highly dispersed L1 2 nanoparticles, leading to precipitation strengthening. Strength-ductility synergy is considered as a long-standing contradiction in high-performance structural materials. Here, we fabricated an equiatomic FeCoNi MEA enhanced by nano-scaled L1 2 precipitates with outstanding mechanical properties via powder metallurgy (P/M) techniques. Compared with the FeCoNi MEA, this precipitation-strengthened FeCoNi MEA exhibits higher yield strength (796 MPa) and ultimate tensile strength (1268 MPa), and maintains moderate ductility of 20.3%. The strength improvement is mainly attributed to the grain refinement and dislocation pinning, caused by densely dispersed L1 2 nanoparticles with a volume fraction of about 48.7 vol%. This work provides a new strategy to design high-performance structural materials. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) usually have a high strength at elevate temperatures. However, their oxidation resistance is inferior for practical applications. Here we proposed a eutectic design of compositionally complex eutectic alloy (CCEA) by adding 10 at. % Ta to the Al 2 Co 28 Cr 20 Fe 25 Ni 25 , the resulting alloy shows a good combination of mechanical properties and oxidation resistance, e.g. a yield strength of 764 MPa and an oxidation resistance rate of 0.0031 mg cm−2h−1 at 800 °C, which outperforms those of RHEAs. The excellent oxidation resistance is attributable to the formation of protective Cr 2 O 3 and CrTaO 4 layer at the surface, which prevents the matrix from further contact with O 2. • A novel, non-equiatomic compositional complex alloy with eutectic structure was prepared by powder metallurgy. • The alloy exhibited an oxidation rate of only 0.0031 mg cm−2h−1 at 800 °C. • The protective Cr 2 O 3 and CrTaO 4 layers generated during oxidation prevents further contact with O 2. • The Laves phase transformed into the Co 0.6 Ta 0.4 phase near the surface of the alloys above 1000 °C. [ABSTRACT FROM AUTHOR]

Refractory high entropy alloys (RHEAs) are promising high temperature structural materials because of their excellent high temperature strength and high melting point. With introducing secondary particles, the high temperature mechanical properties can be further improved. However, its poor ductility limits the industrial application. In the present work, a new ductile NbTaTiV RHEA-based composite reinforced with Ti-C-O particles were in-situ synthesized through spark plasma sintering (SPS). The composite exhibits excellent room temperature compressive properties with yield strength, ultimate strength and fracture strain of 1760 MPa, 2270 MPa and 11%, respectively. A model is presented to study the strengthening mechanism, and the theoretical calculation shows that the dramatically strength enhancement is mainly due to the in-situ formation of Ti-C-O particles. • A (NbTaTiV) BCC /Ti-C-O composite was in-situ synthesized through powder metallurgy method. • The composite exhibits desirable yield strength of 1.76 GPa and ultimate strength of 2.27 GPa with reasonable fracture strain of about 11% at room temperature. • The composite also maintains an outstanding yield strength of 685 MPa at 1000 °C. • A model was present to analyze the strengthening mechanism. [ABSTRACT FROM AUTHOR]

A novel non-equiatomic Al 15.85 Fe 11.15 Co 32.11 Cr 10.76 Ni 30.13 high entropy alloy (HEA) was fabricated via powder metallurgy (P/M) method. The Al 15.85 Fe 11.15 Co 32.11 Cr 10.76 Ni 30.13 HEA exhibits dual-phase microstructure consisting of face-centered-cubic (FCC) and body-center cubic (BCC) phases. The Al 15.85 Fe 11.15 Co 32.11 Cr 10.76 Ni 30.13 HEA has high compressive yield strength of 938 MPa and fracture strength of 3360 MPa, and still maintains moderate fracture strain higher than 40%. Also, the Al 15.85 Fe 11.15 Co 32.11 Cr 10.76 Ni 30.13 HEA has high strength of 518 MPa at the temperature of 600 °C. Microstructural characterization shows that a large number of L1 2 and B2 nanoprecipitates are uniformly dispersed in the FCC and BCC phases, respectively, contributing to the enhancement of the strength of the two phases. The effective combination of FCC and BCC phases eventually leads to the high strength of the Al 15.85 Fe 11.15 Co 32.11 Cr 10.76 Ni 30.13 HEA. This finding provides novel guidance for the development of high-performance structural materials with superior balance of strength and ductility for future industrial applications. • Novel Al 15.85 Fe 11.15 Co 32.11 Cr 10.76 Ni 30.13 HEA was prepared through powder metallurgy method. • The HEA exhibits dual-phase (FCC + BCC) microstructure. • Massive L1 2 and B 2 nanoprecipitates are embedded in the FCC and BCC phases, respectively. • The HEA exhibits high compressive yield strength of 938 MPa at room temperature. • The high strength is attributed to the hierarchically heterogeneous microstructure. [ABSTRACT FROM AUTHOR]

Static recrystallization and texture evolution of the 80% cold-rolled (CR) powder metallurgy (PM) CoCrFeNiN 0.07 high-entropy alloy (HEA) during isothermal annealing were studied. The results show that the CR sheet exhibit a large number of shear bands, severe elongated grains and weak combination of α-fiber, γ-fiber and τ-fiber texture. The static recrystallization temperature of the CR sheet is 700 °C. The recrystallization activation energy is 232.7 kJ mol−1 following the Arrhenius-type relation. When the annealing temperature increase from 750 °C to 950 °C, the average recrystallization grain size increases from 635 nm to 2.7 µm, and the yield strength (YS) reduced from 712 MPa to 572 MPa, ultimate tensile strength (UTS) reduced from 981 MPa to 910 MPa, the elongation (EL) increased from 43% to 57%. Due to high dependence of recrystallization grain orientation on parent crystal, the {111}<112>F texture retained in recrystallized grains during annealing, but with the increase of recrystallization temperature, the recrystallization texture tends to be weak and scattered. • A FCC-type CoCrFeNiN 0.07 high-entropy alloys (HEAs) was fabricated by PM. • Preferred RX nucleation site is shear band, triple connection and grain boundary. • UFG with size of 635 nm were obtained by cold rolling and subsequent annealing. • {111}<112>F texture is retained a lot in RX grains during annealing process. [ABSTRACT FROM AUTHOR]