•The HfNbTaTiZr high entropy alloy produced by arc melting.•After homogenization at 1200°C the alloy had single bcc phase structure.•The homogenized alloy was annealed at 600–1000°C for ...1–100h.•Significant increase of hardness after annealing at 600°C for 10h found.•Hardening is associated with precipitation of nano-sized hcp second phase particles.
The HfNbTaTiZr high entropy alloy was produced by vacuum arc melting, homogenized at 1200°C, and annealed at 600–1000°C for 1–100h. Structure and microhardness of the annealed alloy were investigated. A strong increase of microhardness after aging treatment at 600°C was found. Formation of second hcp phase particles in the bcc matrix after annealing at 600 and 800°C was also revealed. Effect of precipitation of second phase particles on microhardness was analyzed.
Microstructural evolution during cold sheet rolling to 80% thickness strain and annealing at 600–1100 °C for 30 min of the CoCrFeNiMn high entropy alloy doped with 1 at.% of C and resulting ...mechanical properties of the alloy are reported. It is shown that in the initial homogenized (24 h at 1000 °C) condition the alloy has single fcc phase structure. Cold rolling is accompanied by dislocation slip, deformation twinning and formation of shear bands. Annealing at 600 °C after 80% cold rolling results only in partial recrystallization of cold-deformed structure, while an increase of the annealing temperature produces fully recrystallized microstructure. Comparison with the data on undoped CoCrFeNiMn alloy demonstrates that the addition of carbon pronouncedly increases dislocation activity simultaneously retarding deformation twinning during rolling and decreases the fraction of twin boundaries in the annealed condition. The effect of carbon can be attributed to an increase of stacking fault energy of the carbon-containing alloy. Cold rolling results in a substantial strengthening of the alloy; its ultimate tensile strength approaches 1500 MPa, but at the expense of low ductility. Good combination of strength and ductility can be obtained after annealing. For example, after annealing at 800 °C, the alloy has yield strength of 720 MPa, ultimate tensile strength of 980 MPa, uniform elongation of 21% and elongation to fracture of 37%. It is shown that the high strength of the annealed alloy can be attributed to (i) strong grain boundary strengthening; (ii) solid solution strengthening by carbon.
•CoCrFeNiMn high entropy alloy doped with 1 at.% C was produced by vacuum arc melting.•After homogenization annealing at 1000 °C the alloy has single fcc phase structure.•The alloy was cold rolled to 80% thickness strain and annealed at 600–1100 °C.•After annealing at 800 °C the alloy combines high strength with good ductility.•High strength of the annealed alloy mainly is due to strong Hell-Petch strengthening.
Microstructure evolution in high-entropy alloy CoCrFeNiMn during uniaxial compression to a height reduction of true strain of ≈1.4 in the temperature interval 600–1100°C was studied. Although some ...differences was observed in the mechanical behavior of the alloy and the activation energy of deformation in warm (below 800°C) and hot (above 800°C) temperature intervals, microstructure evolution at all studied temperatures was found to be accompanied by discontinuous dynamic recrystallization (dDRX). During hot deformation recrystallization was primary associated with nucleation of new grains on the initial grain boundaries, while in the warm interval dDRX was mainly observed in shear bands. The volume fraction of the recrystallized structure was respectively 0.085 and 0.95 at 600 and 1000°C and the recrystallized grain size was found to be 0.2 and 40.4µm for 600 and 1100°C, respectively.
Four non-equiatomic Fe-(Co, Mn)-Cr-Ni-Al-(Ti) high entropy alloys, namely Fe36Mn21Cr18Ni15Al10, Fe36Co21Cr18Ni15Al10, Fe35Mn20Cr17Ni12Al12Ti4, and Fe35Co20Cr17Ni12Al12Ti4 alloys, were produced by arc ...melting. Structures and compression mechanical properties of the as-cast alloys were examined. The Fe36Co21Cr18Ni15Al10 alloy had mostly a face-centered cubic (fcc) structure, while Fe36Mn21Cr18Ni15Al10 mainly consisted of a body-centered cubic (bcc) matrix with embedded B2 precipitates. An addition of Ti resulted in the formation of L21 precipitates of a cuboidal shape mostly in the Fe35Mn20Cr17Ni12Al12Ti4 and of a plate-like shape in the Fe35Co20Cr17Ni12Al12Ti4 alloys. In addition, a significant amount of the fcc phase (0.17) was found in the latter alloy. Good correlation between the average valence electron concentration (VEC) value and the amount of the fcc phase in the experimental alloys was found. The comparison of the experimental data with results obtained using a Thermo-Calc software and a TCHEA2 database demonstrated a lack of credibility in the L21 phase formation predicting. In terms of the mechanical properties, the Fe36Co21Cr18Ni15Al10 alloy was rather soft, while the Fe36Mn21Cr18Ni15Al10 and Fe35Mn20Cr17Ni12Al12Ti4 alloys had high strength at temperatures of ≤400 °C. The Fe35Co20Cr17Ni12Al12Ti4 alloy had the highest strength among the examined alloys and maintained the strength at temperatures up to 600 °C. The correlation between the mechanical properties and structure of the non-equiatomic Fe-(Co, Mn)-Cr-Ni-Al-(Ti) high entropy alloys and a potential for further improvements of the properties are discussed.
•Fe36(Mn, Co)21Cr18Ni15Al10 and Fe35(Mn, Co)20Cr17Ni12Al12Ti4 alloys were arc melted.•Fe36Co21Cr18Ni15Al10 alloy had mostly fcc structure.•Fe36Mn21Cr18Ni15Al10 alloy was composed of bcc matrix with B2 precipitates.•Fe35(Mn, Co)20Cr17Ni12Al12Ti4 alloys mostly had bcc matrix with L21 precipitates.•Alloys with bcc + B2/L21 structure had high strength at temperatures ≤600 °C.
Structure and mechanical properties of the AlNbTiVZrx (x = 0; 0.1; 0.25; 0.5; 1; 1.5) refractory high-entropy alloys were investigated after arc melting and annealing at 1200°C for 24h. The AlNbTiV ...alloy had a B2 ordered single phase structure. Alloying with Zr resulted in (i) change of the degree of order of the B2 phase; and (ii) precipitation of the Zr5Al3 and C14 Laves ZrAlV phases. The density of the AlNbTiVZrx alloys varied from 5590kgm−3 for the AlNbTiV alloy to 5870kgm−3 for the AlNbTiVZr1.5 alloy. The compression yield strength at 22°C increased with an increase in the Zr content from 1000MPa for the AlNbTiV alloy to 1535MPa for the AlNbTiVZr1.5 alloy. The plasticity raised from 6% for the AlNbTiV alloy to >50% for the AlNbTiVZr0.5 alloy and then dropped to 0.4% for the AlNbTiVZr1.5 alloy. At 600°C, the strongest alloy was also the AlNbTiVZr1.5, whereas, at 800°C, the AlNbTiVZr0.1 alloy demonstrated the maximum strength. The plasticity of the AlNbTiV alloy at 600°C increased up to 14.3%, while the Zr-containing alloys had lower plasticity. At 800°C, all the AlNbTiVZrx alloys could be plastically deformed up to 50% of strain without fracture. Ordering in the alloys and the reasons of a complicated dependence of mechanical properties of the AlNbTiVZrx alloys on the Zr content and temperature were discussed.
Four refractory high entropy alloys with different chemical compositions, which can be calculated as Ti(50-1.5625x)Nb(30-0.9375x)Cr10V10Ni1.5xAlx (x = 0, 5, 7, 10), were prepared by arc melting to ...determine the effect of Ni and Al on the phase composition, structure and mechanical properties. Each alloy was studied in both the as-cast and annealed at 1000 °C for 24 h conditions; compression tests at room temperature or at 800 °C was used to examine mechanical behavior of the alloys and the effect of deformation on microstructure. The replacement of Ti and Nb with Al and Ni resulted in the formation of the Ti, Ni-rich σ-phase and Ti2Ni phases in the bcc matrix in contrast to the ThermoCalc predictions which suggests the formation of the bcc solid solution, B2, and Laves phases. The Ti, Ni-rich σ-phase can't also be expected from the analysis of the corresponding binary and ternary phase diagrams. Annealing did not result in noticeable changes in the microstructure. The formation of the σ and Ti2Ni phases resulted in a considerable increase in strength (from 745 to 1600 MPa) and decrease in ductility (from a thickness reduction ≥50% to fracture in the elastic region) at room temperature. An increase in the testing temperature to 800 °C resulted in softening to and a substantial increase in ductility of all the alloys. Complex relationships between the fraction of the second phases and mechanical properties were discussed.
Microstructure and mechanical properties of the Fe-Mn-Cr-Ni-Al system non-equiatomic high entropy alloys with a different Al content (x = 0–14 at.%) were studied in the present work. The ...Fe40Mn25Cr20Ni15 alloy was composed of the face-centered cubic (fcc) matrix phase with a small amount of coarse body-centered cubic (bcc) particles. Addition of a small amount of Al (x = 2–6) resulted in an increase in the fraction of the bcc phase to 26% and the formation of fine B2 precipitates within the bcc phase. At higher amounts of Al (x = 10 and x = 14) the microstructure consisted of coarse bcc matrix grains with the B2 precipitates inside. The alloys tend to become stronger with an increase in the Al content from 0 to 10 at.%; further increase in Al concentration did not influence strength considerably. The alloys exhibited pronounced softening with an increase in testing temperature from 25 to 400 °C–600 °C. Ductility of the alloys was high enough (>50%) at all temperatures. A quasi-binary Fe40Mn25Cr20Ni15-Al phase diagram was constructed using a ThermoCalc software and a TCHEA2 database; reasonable agreement between the experimental and predicted phase compositions of the alloys was obtained. It was suggested that an addition of the strong bcc-stabilizing and compound-forming Al to a bcc-prone Fe40Mn25Cr20Ni15 alloy is beneficial for the development of the alloys with the disordered bcc matrix and the embedded B2 precipitates having attractive mechanical properties.
•(Fe40Mn25Cr20Ni15)100-xAlx (x = 0–14 at.%) high entropy alloys were arc melted.•X = 0–6 alloys were mixtures of fcc and bcc phases.•X = 10–14 alloys had bcc matrix with B2 precipitates.•Reasonable agreement with ThermoCalc phase diagram was found.•Bcc/B2 alloys had high strength and ductility in compression at T ≤ 400 °C.
Proton migration is a ubiquitous process in chemical reactions related to biology, combustion, and catalysis. Thus, the ability to manipulate the movement of nuclei with tailored light within a ...hydrocarbon molecule holds promise for far-reaching applications. Here, we demonstrate the steering of hydrogen migration in simple hydrocarbons, namely, acetylene and allene, using waveform-controlled, few-cycle laser pulses. The rearrangement dynamics is monitored using coincident 3D momentum imaging spectroscopy and described with a widely applicable quantum-dynamical model. Our observations reveal that the underlying control mechanism is due to the manipulation of the phases in a vibrational wave packet by the intense off-resonant laser field.
The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this ...new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. By comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted.
The structure and energy associated with interfaces between the BCC and HCP lattices (
β
and
α
phase, respectively) in titanium alloys with commonly used
β
stabilizers were analyzed. For this ...purpose, the crystallographic structure of the matching facets of broad, side and end faces was described using misfit dislocations and structural ledges which compensate the mismatch in atomic spacing of the
α
and
β
phases. The effect of the
β
/
α
transformation temperature due to various concentration of
β
stabilizers on periodicity of misfit dislocations and structural ledges was estimated. The van der Merwe approach was used to calculate energy of different matching facets. An increase in the percentage of
β
-stabilizing elements was found to result in a decrease in the lattice-parameter ratio (
a
β
/
a
α
) and an increase in the energy of all faces. The dependence of the interface energy on the
a
β
/
a
α
ratio was for the first time quantified, and insight into the preferred shape of
α
-phase precipitates was obtained.
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