Search

Eutectic high-entropy alloys (EHEAs) have shown good as-cast tensile strength and ductility due to the combination of soft and hard phases. However, the yield strengths of casting EHEAs are less competitive. We here induced precipitation hardening to overcome the above challenge in the casting Ni44Co10Cr12Fe15Al17W2 EHEA. L12 and BCC dual-coherent phases precipitate from the FCC/B2 eutectics of Ni44Co10Cr12Fe15Al17W2, leading to an excellent yield strength of 805 ± 45 MPa with uniform elongation of 17.7 ± 0.9 pct. [ABSTRACT FROM AUTHOR]

Dual-phase high-entropy alloys with excellent room temperature and high-temperature properties have been widely studied as potential high-temperature structural materials. However, interface weakening causes its high-temperature performance to decline at higher temperatures, severely limiting further development. In this study, a series of Al17Cr10Fe36Ni36Mo1Hfx (x = 0, 0.03, 0.15, 0.3, 0.5, and 0.8 at%) alloys were prepared to study the effect of Hf content on the microstructure and mechanical properties of the matrix alloy. The results indicate that with the addition of the Hf, the Hf-rich phase began to precipitate at the interface and inside the B2 phase in the matrix alloy. In contrast, the morphology of both the FCC and B2 phases had no noticeable change. With the increase in Hf content, the high-temperature strength and ductility of the alloy first increased and then decreased, while the room temperature performance remained almost unchanged. Benefiting from the hindrance of the Hf-rich phase to grain boundary sliding and dislocation movement during high-temperature deformation, the tensile strength, yield strength, and plasticity of the matrix alloy increased from 474 MPa, 535 MPa, and 8.7% to 816 MPa, 923 MPa, and 42.0% for the Al17Cr10Fe36Ni36Mo1Hf0.5 alloys, respectively. This work provides a new path for designing a high-entropy alloy with excellent high-temperature mechanical properties. [ABSTRACT FROM AUTHOR]

• A casting eutectic high entropy alloy Ni 30 Co 30 Cr 10 Fe 10 Al 18 W 2 was designed and prepared. • The alloy consists of soft FCC and hard B2 eutectic phases with the semi-coherent interface. • The alloy possesses a tensile strength of 1266.5 MPa and an elongation of 20.3% in the as-cast condition. Mechanical properties of casting alloys are generally limited. To make casting alloys applicable for a high level of service environments, a novel casting eutectic high entropy alloy (EHEA) with excellent mechanical properties is proposed. The hierarchical microstructures are with fine regular lamellar eutectic and coarse irregular eutectic. The eutectics consist of face-centered cubic (FCC) and ordered body-centered cubic (B2) phases with the semi-coherent interface. In the as-cast state, it shows a tensile strength of 1266.5 MPa and elongation of 20.3%. The unusual as-cast properties make it possible to manufacture high performance products by direct casting. [ABSTRACT FROM AUTHOR]

With excellent compressive mechanical properties, FeNiCrAl medium entropy alloys with multi-principal components have attracted extensive attention in recent years. However, the limited tensile ductility of FeNiCrAl medium entropy alloys is the bottleneck for their industrial applications. In this work, dual phases of FCC + B2 and BCC + B2 were modulated in FeNiCrAl medium entropy alloys for excellent tensile behaviors. In the as-cast state, the tensile yield strength and ultimate tensile strength are 1140 MPa and 1423 MPa, respectively, with a uniform elongation of 6.0%. • As-cast dual phases FeNiCrAl medium entropy alloys are designed for excellent tensile behavior. • Dual phases of FCC+B2 and BCC+B2 are modulated by changing the valence electron concentration via the ratio of Fe/Ni. • Fe 47 Ni 26 Cr 10 Al 17 alloy has a fine nanostructure with BCC+B2 dual phases. • As-cast Fe 47 Ni 26 Cr 10 Al 17 alloy shows yield strength of 1140 MPa and uniform elongation of 6.0%. [ABSTRACT FROM AUTHOR]

The category and morphology of precipitates are essential factors in determining the mechanical behaviors of aluminum alloys. It is a great challenge to synthetically modulate multiple precipitates to simultaneously improve strength and ductility. In the present work, by optimizing the precipitations of the GP zone, θ'-approximant and θ' phase for an Al-Cu-Mn alloy, a high tensile strength of 585 MPa with large elongation of 12.35% was achieved through pre-deformation and aging. The microstructure evolution pattern was revealed by detailed characterizations of scanning electron microscopy and transmission electron microscopy. It was found that such high tensile strength of the samples was due to a combination of strengthening by the high density of dispersive fine precipitates and dislocations, and the high elongation to failure was primarily attributed to the multimodal precipitates and elimination of precipitation-free zones along the grain boundaries. The strategy proposed here is a promising way of preparing ultra-strong Al-Cu-Mn alloys. [ABSTRACT FROM AUTHOR]

Eutectic high entropy alloys (EHEAs) exhibit excellent mechanical properties in the as-cast condition. In this paper, Mo element was chosen to further strengthen the EHEAs by solid solution strengthening. The microstructures, phase compositions and mechanical properties of Co30Cr10Fe10Al18Ni32 − xMox (x = 0, 1, 2, 3) alloys were investigated. It was found that Mo acts as a solid solution strengthening element in the face-centered cubic (FCC) and body-centered cubic (BCC) phases. Meanwhile, Mo can promote the formation of the primary BCC phase. Among all alloys, the alloy with Mo (x = 2) has the highest fracture tensile strength of 1250 MPa and the acceptable elongation of 14%. [ABSTRACT FROM AUTHOR]

• Phase-selective recrystallization and aging was applied to the FeNiCrAl alloy. • Effect of aging on the microstructure and mechanical properties were studied. • The tensile elongation significantly increases via phase-selective recrystallization. • The aged alloy shows ultimate strength of 1369.0 MPa and elongation of 23.0%. Phase-selective recrystallization process has been confirmed as an effective way to improve the ductility of dual-phase alloys. Here, the tensile property of a low-cost dual-phase Fe 37 Ni 36 Cr 10 Al 17 alloy was significantly improved via phase-selective recrystallization and aging. The equiaxed microstructure was obtained after phase-selective recrystallization and the tensile elongation significantly increases compared with as-cast alloy. Furthermore, the tensile strength increased to 1369.0 MPa and elongation increased to 23.0% by aging. The comprehensive property shows great potential applications for industrial prospects. [ABSTRACT FROM AUTHOR]

Single-phase equiatomic CoCrFeNi high entropy alloy (HEA) is a promising high-entropy base with high tensile ductility and fracture toughness. However, the equal molar fraction of these elements is not a sufficient and necessary condition to obtain a single solid solution with high entropies. Instead, our combination of both calculated phase diagram (CALPHAD) calculations and experimental verifications indicate that the single phase region in the Co-Cr-Fe-Ni HEA system can be extended from a point to a large single phase solid solution island. The significance of this study is that HEAs can be designed with a high design diversity. [ABSTRACT FROM AUTHOR]

Very recently, a method of phase-selective recrystallization has been proposed to significantly increase the ductility of eutectic alloys. Different from the conventional methods, such as adding modifiers and severe plastic deformation, phase-selective recrystallization is a simple way to control the microstructures with selective recrystallization of the soft phase but refining the hard phase. In this paper, we reveal the microstructure evolution in the phase-selective recrystallization treatment of Al–Si alloys. The results show that through phase-selective recrystallization, the microstructure of the eutectic Si phase with high degree of spheroidization and fine grains of the α-Al matrix can be obtained. Simultaneously, the refined hard Si particles and the soft α-Al grains brought the unusual tensile elongation of 24%, triple of that in as-cast state. Meanwhile, the ultimate tensile strength increased from 208 MPa to 291 MPa. The performance of Al–Si alloy with phase-selective recrystallization is superior to all previous treatments and can be used to produce high performance Al–Si alloy sheet with large scale. • High-performance A357 Al–Si alloy was simply prepared by cyclic rolling and recrystallization. • Cyclic rolling and recrystallization simultanously refined the eutectic Si and α-Al matrix. • The elongation and strength of A357 Al–Si alloy were simultanously enhanced. • Cyclic rolling and recrystallization showed great potentical in industrial application. [ABSTRACT FROM AUTHOR]