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Achieving high strength in Mg alloys is usually accompanied by ductility loss. Here, a novel Mg 97 Y 1 Zn 1 Ho 1 at.% alloy with a yield strength of 403 MPa and an elongation of 10% is developed. The strength-ductility synergy is obtained by a comprehensive strategy, including a lamella bimodal microstructure design and the introduction of nano-spaced solute-segregated 14H long-period stacking-ordered phase (14H LPSO phase) through rare-earth Ho alloying. The lamella bimodal microstructure consists of elongated un-recrystallized (un-DRXed) coarse grains and fine dynamically-recrystallized grains (DRXed regions). The nano-spaced solute-segregated 14H LPSO phase is distributed in DRXed regions. The outstanding yield strength is mainly contributed by grain-boundary strengthening, 18R LPSO strengthening, and fiber-like reinforcement strengthening from the nano-spaced 14H LPSO phase. The high elongation is due primarily to the combined effects of the bimodal and lamellar microstructures through enhancing the work-hardening capability. [ABSTRACT FROM AUTHOR]

Multicomponent high‐entropy alloys (HEAs) can be tuned to a simple phase with some unique alloy characteristics. HEAs with body‐centered‐cubic (BCC) or hexagonal‐close‐packed (HCP) structures are proven to possess high strength and hardness but low ductility. The faced‐centered‐cubic (FCC) HEAs present considerable ductility, excellent corrosion and radiation resistance. However, their strengths are relatively low. Therefore, the strategy of strengthening the ductile FCC matrix phase is usually adopted to design HEAs with excellent performance. Among various strengthening methods, precipitation strengthening plays a dazzling role since the characteristics of multiple principal elements and slow diffusion effect of elements in HEAs provide a chance to form fine and stable nanoscale precipitates, pushing the strengths of the alloys to new high levels. This paper summarizes and review the recent progress in nanoprecipitate‐strengthened HEAs and their strengthening mechanisms. The alloy‐design strategies and control of the nanoscale precipitates in HEAs are highlighted. The future works on the related aspects are outlined. [ABSTRACT FROM AUTHOR]

Reduced-activation refractory complex concentrated alloys (RARCCAs) are promising for nuclear industrial applications due to their high strength, corrosion resistance, and irradiation resistance. However, the poor phase stability of the matrix and formation of a brittle second phase result in a poor strength-ductility balance. A novel Ti 0.5 Hf 0.25 Ta 0.25 RARCCA with a single bcc (body-centered cubic) phase possessing excellent strength and ductility synergy is successfully developed in this study by deliberately combining the "d-electron" method and the empirical parameters calculation. The yield and tensile strengths are 903 and 929 MPa, respectively, with an excellent ductility of approximately 22%. A new type of ω precipitate with a small size (∼1.7 nm) is introduced, contributing to a strength increment of approximately 150 MPa through shearing mechanism without sacrificing ductility. Dislocation slip dominates the deformation during tension at room temperature. • A new alloy design strategy combining the "d-electron" method and the empirical parameters calculation is developed. • A novel Ti 0.5 Hf 0.25 Ta 0.25 reduced-activation refractory complex concentrated alloy with single BCC phase is designed. • High density nano-sized ω precipitates increase the yield strength of about 150 MPa without sacrificing ductility. • Bo-Md diagram is introduced to evaluate the phase stability of refractory complex concentrated alloys. [ABSTRACT FROM AUTHOR]

The effects of cold deformation on the microstructure, texture evolution and mechanical properties of TB8 alloy during cold rolling (CR) were investigated. The results show that grain size decreases with the increase in thickness reduction. Meanwhile, the textures change from initial {110}<001> and {113}<332> to α-fiber components ({112}<110>, {113}<110>) and {001}<110> orientation after cold rolling to a thickness reduction of 50%. Increasing the thickness reduction to 67%, α-fiber textures are enhanced along with the appearance of γ-fiber textures. Increasing the thickness reduction further to 83%, γ-fiber textures become dominated. Both grain refinement and texture components contribute to the enhancement of strength after cold rolling. The effect of textures on the mechanical properties are discussed briefly. [ABSTRACT FROM AUTHOR]

A TA1 (Ti alloy)/low alloy steel (LAS) composite plate was manufactured by explosive welding. The effects of the bonding interface microstructure on the mechanical properties and fracture behavior of the composite plate were investigated. The results show that the interface has a wavy structure with intermetallic compounds (IMCs) enclosed by a steel matrix. The metallurgical bonding interface was achieved by local diffusion, with a several micrometer-thick diffusion layer. Two kinds of microcracks were formed in the IMC region and the diffusion interface. Microcracks in the IMC region propagate with difficulty due to the impediment of the IMC/steel interface. The microcracks initiated at the interface need to propagate into the fine-grain steel matrix before crack connection and delamination. The shear strength of the TA1/LAS composite plate was over 350 MPa. The composite plate could be bent up to the equipment limit (135 degrees). Excellent mechanical properties were obtained since the crack propagation was hindered by the refined or elongated steel grains induced during explosive welding. [ABSTRACT FROM AUTHOR]

In this work, the exceptional strength-ductility synergy of a dual-phase high entropy alloy (HEA) is achieved by architecting complex microstructures. The HEA rolled at 700 °C shows the yield strength and tensile strength as high as 1580 MPa and 1854 MPa with ductility of ∼18.4%. Different flow stress regions (face-centered cubic (FCC) and body-centered cubic (BCC) phases) divided by complex microstructures lead to strong hetero-deformation-induced strain hardening. The dispersed micro-strain band and the precipitates buffering the dislocation in front of the heterogeneous phase boundary also help to improve the ductility. In addition, utilizing the sensitivity difference between FCC and BCC phases for dislocation accumulation, more dislocations are accumulated in FCC phase to reduce the mechanical incompatibility with BCC phase and fully release the strain hardening ability. The strategy of architecting complex microstructures and selectively modifying phases will be beneficial to the development of high-performance dual-phase alloys. [ABSTRACT FROM AUTHOR]

Refractory high entropy alloys (RHEAs), mainly consisting of high-melting-point alloying elements such as Zr, Ti, Nb, Ta and V, are promising candidates in the field of nuclear engineering. However, the poor room-temperature mechanical properties of the REHAs limit their engineering applications. In this study, Zr 35 Ti 30 Nb 20 Al 10 Ta 5 and Zr 35 Ti 30 Nb 20 Al 10 V 5 RHEAs were developed. Ductile body-centered-cubic (BCC) matrixes were obtained by regulating the valence electron concentration (VEC). The introduction of Al elements promoted the formation of fine and dispersedly distributed B2 nanoprecipitates in the BCC matrix to enhance the strength. At room temperature, the cast Zr 35 Ti 30 Nb 20 Al 10 Ta 5 and Zr 35 Ti 30 Nb 20 Al 10 V 5 alloys possess tensile yield strengths of ∼850 MPa/848 MPa with elongations of ∼25%/16%. The high yield strength is mainly contributed by solid solution strengthening and nanoprecipitate strengthening. • Two novel Zr-rich refractory high-entropy alloys were designed. • Ductile BCC matrixes were obtained by regulating the valence electron concentration. • The cast alloys possess high yield strengths and elongations. [ABSTRACT FROM AUTHOR]

High/medium entropy alloys (HEAs/MEAs) are good candidates for nuclear applications due to the excellent mechanical properties, good corrosion resistance and radiation resistance. In this work, a novel cobalt-free MEA was developed by introducing L1 2 nanoprecipitates. The microstructure evolution and radiation tolerance were evaluated after bombarded using 3 MeV Fe11+ ions at 500 °C. The evolution of nanoprecipitates was closely related to the irradiation dose, and dominated by irradiation-enhanced diffusion and ballistic dissolution mechanism. For the solid-solution MEA (without L1 2 nanoprecipitates), irradiation hardening occurred due to the irradiation-induced formation of precipitates, voids and dislocation loops. However, in MEA with L1 2 nanoprecipitates after aging, irradiation induced dissolution and reprecipitation of nanoprecipitates were observed. Different from the solid-solution MEA, the hardness kept almost unchanged in the aging sample after irradiation. The swelling rate of the solid-solution sample after irradiation is 9.4 × 10−6 %/dpa, while no swelling occurs in the aging sample under the same irradiation condition. Besides, the average size and number density of dislocation loops in the aging sample decreased by ∼ 40% and ∼ 28%, compared with the solid-solution sample. The precipitation and dissolution of nanoprecipitates substantially improved the radiation tolerance of the cobalt-free MEA. [ABSTRACT FROM AUTHOR]

Limitations of strength and formability are the major obstacles to the industrial application of magnesium alloys. Here, we demonstrate, by producing the duplex phases and fine intermetallic particles in composition-optimized superlight Mg-Li-Al alloys, a unique approach to simultaneously improve the comprehensive mechanical properties (a strength-ductility balance). The phase components and microstructures, including the size, morphology, and distribution of precipitated-intermetallic particles can be optimized by tuning the Li content, which strongly influences the work-hardening behavior and tension-compression yield asymmetry. [ABSTRACT FROM AUTHOR]

Texture evolution is strongly dependent on the deformation mode during thermo-mechanical treatments. In this paper, we report the texture evolution in a duplex Mg–Li alloy. The results provide an evidence of deformation mode transition in the hexagonal-close-packed (hcp) α phase with various thickness reductions. The activation sequence of deformation modes is basal slip first, and then pyramidal slip during hot-rolling to a thickness reduction of 40%. The relative activity of slip decreases with further thickness reduction. After annealing, basal texture is strengthened and pyramidal component disappears due to static recrystallization and grain growth. The microstructure, specifically texture evolution in both hcp α and body-centered cubic (bcc) β phase and their effects on mechanical properties are quantitatively analyzed and assessed. [ABSTRACT FROM AUTHOR]

The grain refinement efficiency of Mg–5Li–3Al alloy inoculated by Al–5Ti–1B master alloy and the influences of grain size on the mechanical properties were investigated. With the addition of 1.0 wt% Al–5Ti–1B, the average grain size of Mg–5Li–3Al alloy decreases markedly from ~120 μm to 50 μm, leading to significant increases in both strength and elongation. The tensile yield strength (YS), ultimate tensile strength (UTS) and elongation increased from 82 MPa, 154 MPa and 7.8% to 110 MPa, 216 MPa and 12.2%, respectively. XRD and EDS analysis show that Al–5Ti–1B master alloy is composed of α -Al, Al 3 Ti and TiB 2 . Crystallographic calculations and EDS analysis indicate that TiB 2 particles are the potent heterogeneous nucleating substrates for α -Mg grains, which is the main reason for grain refinement. In addition, solute element, Ti also plays an important role in grain refinement. [ABSTRACT FROM AUTHOR]

• The effect of Al/Ti ratio in a series of HEAs was investigated. • Layer-like L1 2 precipitates formed around the GBs, and spherical L1 2 precipitated in the grains. • The coarse L1 2 GB phases transform to Heusler phase due to the local supersaturation of Al and Ti. • The small amount of small size Heusler phases at the GBs have no negative effect on the plasticity. L1 2 -structured Ni 3 (Al, Ti) precipitates are promising strengthening particles in face-centered-cubic high entropy alloys (HEAs). However, if the Al/Ti ratio (R) is not carefully controlled, brittle intermetallic compounds can form, especially at the grain boundaries (GBs). In this study, a series of Ni 35 (CoCrFe) 55 Al x Ti 10−x HEAs with different R values, R = x/(10-x), were prepared, and the evolution of precipitates and their effects on the mechanical properties were investigated. The dispersed spherical precipitates within the grains act as an effective barrier to dislocation slip, producing high strength. However, increasing R (increasing Al) reduces the volume fraction of the precipitates within the grains, resulting in a decrease of yield strength. Both experimental measurements and first-principles calculations show that Al, Ti and Ni segregate to the GBs. This leads to the formation of L1 2 precipitates at the GB that, upon aging, coarsen to layer-like structures. When R ≥ 3 the local supersaturation of Al and Ti also leads to formation of a Heusler phase at the GBs, which reduces the ductility. However, when R > 3.5 the volume fraction of the Heusler phase decreases, and the plasticity increases again. These findings provide important guidance and inspire new strategies for the microstructural control in precipitate-strengthened HEAs. [ABSTRACT FROM AUTHOR]

• A new Ni 35 (CoFe) 55 V 5 Nb 5 (at.%) high entropy alloy was developed with an excellent strength and ductility synergy. • A novel L1 2 -Ni 3 Nb nano-precipitate is introduced, which is completely different from the conventional L1 2 -Ni 3 Al and D0 22 -Ni 3 Nb. • First-principles calculations show that some ni and nb atoms are substituted by Co, Fe, and V, and the formation energy of L1 2 -Ni 3 Nb is lower than D0 22 -Ni 3 Nb, forming (Ni 24 Co 18 Fe 6) 3 (Nb 10 V 4 Fe 2) nano-precipitates with an L1 2 crystal structure. • The novel bifunctional nano-precipitates, not only improve the strength by hindering dislocation slip, but also reduce the stacking fault energy of the matrix, changing the deformation mode of the alloy. High-entropy alloys (HEAs) with a single-phased face-centered-cubic structure possess excellent plasticity but generally low strength. Precipitation strengthening is one of the most promising methods to improve the strength of alloys. However, plagued by a nerve-wracking fact that strength-ductility trade-off frequently limits the improvement of alloy properties. To overcome this problem, a new Ni 35 (CoFe) 55 V 5 Nb 5 HEA with an excellent strength and ductility synergy was developed by introducing a novel bifunctional L1 2 -Ni 3 Nb nano-precipitate. This HEA exhibits a high yield strength of 855 MPa, ultimate tensile strength of 1,302 MPa and marvelous elongation of ∼ 50%. First-principles calculations show that the (Ni 24 Co 18 Fe 6) 3 (Nb 10 V 4 Fe 2) nano-precipitate with a L1 2 structure possesses lower formation energy than that with D0 22 structure. The novel nano-precipitates provide two-fold functions. On the one hand, L1 2 -(Ni 24 Co 18 Fe 6) 3 (Nb 10 V 4 Fe 2) nano-precipitates have a high anti-phase boundary energy, contributing to a significant increment in the yield strength through precipitation strengthening. More importantly, the precipitation of the precipitates lowers the stacking fault energy (SFE) of the alloy matrix, contributing to the excellent work-hardening ability and large plasticity through activating the continuous formation of SF networks and Lomer-Cottrell locks during deformation. The strategy to introduce the novel bifunctional nano-precipitates paves a new way to enhance the strength-ductility synergy of alloys. [Display omitted]. [ABSTRACT FROM AUTHOR]

• The incoherent B 4 C/Al 2 O 3 phase interface was replaced by the well-bonded semi-coherent B 4 C/Al interface. • Both the tensile strength and elongation of the as-rolled composite were increased compared with the as-sintered composite. • The improvement of interface Al 2 O 3 nanoparticles distribution during hot rolling improved the mechanical properties. • The dispersion of Al 2 O 3 nanoparticles in the grain improved the dislocation storage ability, hence increase the ductility. B 4 C/Al composites with a high B 4 C content of 30 wt% were successfully fabricated by hot pressing sintering followed by hot rolling. The influence of hot rolling on the microstructure, mechanical properties, anisotropy and the interfacial conditions of the B 4 C/Al composites were systematically investigated. The improvement of the interfacial Al 2 O 3 nanoparticles distribution during hot rolling increased both the strength and ductility. After sintering of B 4 C/Al composites, some Al 2 O 3 nanoparticles aggregated together at the interface between B 4 C and Al matrix, lowering the interface bonding strength between B 4 C and Al matrix. The Al 2 O 3 nanoparticles dispersed into the Al grain interior after rolling, leading to a well bonding interface between B 4 C particles and the Al matrix. In addition, the dispersion of Al 2 O 3 nanoparticles into the Al grain interior contributed to the strength through Orowan strengthening and ductility through the enhancement of dislocation storage ability. The strengthening and toughening mechanisms of the composites are discussed in detail. [ABSTRACT FROM AUTHOR]

The microstructure, interface reactions and mechanical properties of the Q345 steel/Al/Zr bonding interface were investigated. The thicknesses of the reaction layer in both Al/Fe and Al/Zr interfaces are temperature-dependent, with a higher temperature yielding a larger thickness. Both experimental results and thermodynamic calculation confirmed that the diffusion transition regions near the Al/Fe and Al/Zr interfaces mainly consist of Al 5 Fe 2 and Al 3 Zr with thin Al 3 Fe and Al 3 Zr 2 transitional phases, respectively. The growth kinetic equations of Al 5 Fe 2 and Al 3 Zr as a function of temperature were investigated. The fitted curves from the equations well agree with the experimental results. The hardness of Al 5 Fe 2 is higher than Al 3 Zr and the base materials. The propagation of shear crack occurs within Al 5 Fe 2. Optimized shear strength can be obtained by controlling the thickness of reaction layer. The grain growth and fracture mechanisms of Al 5 Fe 2 and Al 3 Zr at the interfaces were also discussed based on electron back scattering diffraction (EBSD) analysis of both reaction layers and fracture morphology. [ABSTRACT FROM AUTHOR]