Nanocrystalline CoCrFeNiMn high-entropy alloy with tunable ferromagnetic properties

A nanocrystalline CoCrFeNiMn high-entropy alloy(nc-HEA)with nano-multiphase structure was prepared by inert gas condensation(IGC)using a laser evaporation source.Encouragingly,the laser-IGC nc-HEA exhibits unexpected ferromagnetic behavior and the Curie temperature(T_(c))increased nearly 10 times compared to any CoCrFeNiMn HEAs prepared by various other methods.In addition,the saturation magnetization(M_s)and T_(c)of the laser-IGC nc-HEA can be controlled via heat treatment,which is resulting from the formation and structural evolution of magnetic nanophases during annealing.This work widens the design toolbox for high-performance nc-HEAs based upon laser-IGC technique.

Ultrahard BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy formed by nanoscale diffusion-induced phase transition

In the current work,the BCC-AlCoCrFeNi bulk nanocrystalline high-entropy alloy(nc-HEA)with ultrahigh hardness was formed by nanoscale diffusion-induced phase transition in a nanocomposite.First,a dual-phase Al/CoCrFeNi nanocrystalline high-entropy alloy composite(nc-HEAC)was prepared by a laser source inert gas condensation equipment(laser-IGC).The as-prepared nc-HEAC is composed of well-mixed FCC-Al and FCC-CoCrFeNi nanocrystals.Then,the heat treatment was used to trigger the interdiffusion between Al and CoCrFeNi nanocrystals and form an FCC-AlCoCrFeNi phase.With the increase of the annealing temperature,element diffusion intensifies,and the Al Co Cr Fe Ni phase undergoes a phase transition from FCC to BCC structure.Finally,the BCC-AlCoCrFe Ni bulk nc-HEA with high Al content(up to 50 at.%)was obtained for the first time.Excitingly,the nc-HEAC(Al-40%)sample exhibits an unprecedented ultra-high hardness of 1124 HV after annealing at 500℃ for 1 h.We present a systematic investigation of the relationship between the microstructure evolution and mechanical properties during annealing,and the corresponding micro-mechanisms in different annealing stages are revealed.The enhanced nanoscale thermal diffusion-induced phase transition process dominates the mechanical performance evolution of the nc-HEACs,which opens a new pathway for the design of high-performance nanocrystalline alloy materials.

In situ study on medium-range order evolution during the polyamorphous phase transition in a Pd-Ni-P nanostructured glass

Engineering multiscale structural hierarchies in glassy alloys enable a broad spectrum of potential applications.Metallic glasses were born in hierarchical structures from atomic-to-nanometer scales.However,the frozen-in structures in traditional metallic glasses prepared by rapid quenching techniques are challenging to tailor.Here,we show that a PdNiPbulk nanostructured glass of polyamorphous interfacial structures was prepared by inert-gas condensation with a laser evaporation source,and its multiscale structures could be engineered.In-situ scattering experiment results reveal polyamorphous phase transitions occurred in the interfacial regions,which are accompanied by the evolution of medium-range order and the nanoscale heterogeneous structures during the condensation process of glassy nanoparticles under high pressure and the following heating process.Moreover,changes in the cluster connectivity resulting from repacking of the local ordering induced by pressure and temperature could be observed.The thermophysical and mechanical properties,including boson peaks,hardness,and elasticity modulus,could be changed as a function of heat-treatment parameters.Our findings would shed light on the synthesis of bulk nanostructured glassy alloys with tailorable thermodynamic and dynamical behavior as well as mechanical properties based on the understanding of metastability for polyamorphous interfacial phases.

Enhanced activity and durability of FeCoCrMoCBY nanoglass in acidic hydrogen evolution reaction

In the present work,a multi-element nanoglass(m-NG)of FeCoCrMoCBY is obtained first time by the laser ablation combined with inert gas condensation(laser-IGC)technique.Compared with the conventional rapid-quenched metallic glass(MG)with identical composition,the Fe-based m-NG demonstrates a superior performance as a self-supported electrocatalyst for hydrogen evolution reaction(HER)in acidic solution.The enhanced HER activity of m-NG is proposed to be closely related to its high en-ergy states,which is originated from the unique inhomogeneous nanostructures with a high density of low-coordinated atoms.Additionally,the Fe-based m-NG exhibits an outstanding comprehensive catalytic performance even beyond the commercial Pt/C catalyst in long-term test due to its self-optimization ability.This work not only opens the way to the preparation of m-NGs by the novel laser-IGC technique,but also makes a great contribution to developing low-cost,high-efficient,and super-durable HER electrocat-alysts in acidic environment.