Solidification microstructures and solidification modes in different austenitic Fe-Mn-Si-Cr-Ni shape memory alloys were investigated. Based on these results, a new set of Cr
eq
and Ni
eq
equations ...(Cr
eq
= Cr + 1.5Si; Ni
eq
= Ni + 0.164Mn + 22C) were developed. The above results show that Mn is still an austenite former in austenitic Fe-Mn-Si-Cr-Ni alloys containing above 12 wt pct Mn and 4 wt pct Si, but its effect is weaker than that in austenitic stainless steels with lower Mn content.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The effects of thermally induced cyclic γ ↔ ε transformation on microstructures and shape memory effect (SME) are investigated in a quenched Fe14Mn5.5Si8.0Cr5.0Ni alloy. The results show that the ...annealing at 773 K remarkably improves the SME in the quenched alloy. One thermal cycling between 290 and 773 K remarkably increases the SME, but the further thermal cycling hardly improves the SME. The reason is that the amount of thermal ε martensite remarkably reduces after annealing at 773 K, but it hardly changes with the further increase of thermal cycling between 290 and 773 K. The pre‐existing thermal ε martensite not only prevents the occurrence of stress‐induced ε martensitic transformation but also promotes the formation of α′ martensite.
A optical micrograph showing some lenticular α′ martensite (dark) produced inside the block thermal ε martensite (white) and many granular α′ martensite (dark) introduced at the intersections of different direction ε martensite bands after 5% deformation in a quenched Fe14Mn5.5Si8.0Cr5.0Ni alloy.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Recent years have witnessed an explosive increase in the exploration of single atom catalysts (SACs) because of their high catalytic activity, selectivity, and maximal atom utilization. In this work, ...we systemically investigated the adsorption and dissociation of O
2
molecules on a series of transition metals anchored on nitrogen-doped graphene as SACs by using density functional theory (DFT) calculations, aiming at screening highly efficient nanocatalysts toward the oxygen reduction reaction (ORR). Our calculations demonstrated that Ag, W, Re, and Os single atoms cannot be stably anchored on nitrogen-doped graphene. Furthermore, physical adsorption is observed between O
2
molecules and Ni, Cu, Pd, Pt, and Au SACs, thus leading to catalytic inactivation. In contrast, O
2
molecules can obtain more charges from Cr, Mn, Mo, and Tc SACs with the side-on absorption configuration than from the rest of the SACs with the end-on configuration, thus being beneficial to the dissociation of O
2
. By overall consideration of the reaction energy, energy barrier, and free energy, Mn SACs should be the optimal graphene-supported nonprecious metal SACs for the ORR. These results are helpful for comprehensive understanding of the interaction between O
2
molecules and transition metal single atoms on graphene-based supports and provide new insights into design and application of cost-effective transition metal SACs.
Transition metal single atoms anchored on nitrogen-doped graphene toward the oxygen reduction reaction have been screened.
We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we ...examined whether the Cr
eq
/Ni
eq
equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software
®
together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software
®
together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Cr
eq
/Ni
eq
equation should be developed or the thermodynamic database of Thermo-Calc software
®
should be corrected.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
To solve the problem of poor wear resistance in conventional Hadfield steels under medium and low stress, a new kind of steel with high silicon and high manganese Fe-17Mn-6Si-0.3C was designed and ...its wear resistance was studied. The results showed that it exhibited better wear resistance than conventional Hadfield steel in both dry friction and abrasive friction. The better wear resistance of the new steel with high silicon and high manganese resulted from the stressinduced γ→ε martensitic transformation.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
As an emerging family of two-dimensional (2D) materials, transition metal borides (MBenes) have attracted increasing interest due to their potential applications in electrochemistry, especially ...electrocatalysis. In this work, we addressed six MB (M = Sc, Ti, V, Cr, Mo and W) monolayers as catalysts to explore their electrocatalytic activity for the nitrogen reduction reaction (NRR) using first-principles calculations. Our results demonstrated that N
2
molecules could be strongly adsorbed on these MB monolayers to provoke the NRR process. Furthermore, we examined five possible catalytic reaction pathways of the NRR,
i.e.
, the alternating, distal, and three mixed pathways, on the MB monolayers with N
2
adsorption (both side-on and end-on) configurations, and screened out three highly efficient NRR catalysts: VB, CrB, and MoB monolayers with the onset potential of −0.396, −0.277, and −0.403 V, respectively. By comparison of the limiting potentials, the most effective reaction pathways of the NRR were ascertained to be the alternating pathway on the VB monolayer with the end-on configuration and the mixed I pathway on the CrB monolayer with the end-on configuration and on the MoB monolayer with the side-on configuration. Our work sheds light on the electrocatalytic mechanisms of the NRR on 2D MBenes, and provides a theoretical foundation for developing highly efficient MBene electrocatalysts for the NRR.
We explored the electrocatalytic mechanisms of N
2
conversion into ammonia on six MB (M = Sc, Ti, V, Cr, Mo, and W) monolayers and screened out three MB monolayers (VB, CrB, and MoB monolayers) with high electrocatalytic activity for the NRR.
With the rapid development of rechargeable lithium-ion batteries, the search for highly efficient electrode materials has become an ever-growing need for high power density and fast charge-discharge ...rate to meet the future challenges of energy storage. Two-dimensional MXenes exhibit good electrical and electrochemical properties and are very attractive candidates for anode materials. In this article, we addressed ordered double-metal pristine TiVC and functionalized TiVCT
2
(T = O, S, F, or OH) MXenes and investigated their electrochemical properties by using density functional theory calculations. Our results reveal that these ordered MXenes all exhibit metallic characteristics with high electronic conductivity. The diffusion barrier of a Li ion is only 15 meV on the Ti surface and 14 meV on the V surface of the pristine TiVC monolayer. However, functional group terminations markedly increase the Li ion diffusion barrier on TiVC monolayers. Among all the group functionalized TiVCT
2
monolayers, the TiVCS
2
monolayer exhibits the lowest diffusion barrier of a Li ion (0.191 eV on the Ti surface and 0.186 eV on the V surface). Furthermore, the open circuit voltages of Li ions on both TiVC and TiVCS
2
monolayers fall in the range of 0-1.0 V, which may prevent the dendrite formation of alkali metals in the charge/discharge process. Therefore, ordered pristine TiVC and functionalized TiVCS
2
monolayers should be promising candidates as anode materials for lithium-ion batteries.
We investigated the electrochemical performance of pristine and functionalized ordered TiVC monolayers as highly efficient anode materials for lithium-ion batteries.
•The Fe2Nb phase at grain boundaries deteriorated the oxidation resistance of the AFA steel at above 1273 K in air.•The pre-aging treatment could improve the oxidation resistance of Nb-containing AFA ...steel.•The B2-NiAl phase precipitates play an important role for the formation of Al2O3 scale in the AFA steels.
To know reason for negative effect of Nb addition on oxidation resistance in alumina-forming austenitic stainless steels at high temperature, effects of Nb addition on microstructural evolution and oxidation resistance were investigated in Fe-25Ni-10Cr-4.5Al based steels after oxidation at 1323 K. The results showed that the degraded oxidation resistance due to the Nb addition resulted from suppressed outward diffusion of Al atoms by formation of Fe2Nb phase. Pre-aging at 1223 K could improve the oxidation resistance of the Nb-containing Fe-25Ni-10Cr-4.5Al steel due to the pre-precipitated B2-NiAl phase.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
It remains unclear whether a negative dependence of shape memory effect (SME) still exists on the density of annealing twin boundary (ATB) in FeMnSi-based alloys during special heat treatments ...without optimal parameters. To address this issue, the evolutions of grain size and martensite amount in an Fe-14.5Mn-5.5Si-8.2Cr-5.2Ni-0.016C alloy were investigated in addition to the evolution of ATB density during the special heat treatments, i.e. training and thermomechanical treatment with different annealing temperatures. The results showed that the SME still showed a strong negative dependence on the ATB density independent of the special heat treatments. An obvious positive dependence of SME existed on the density of low angle grain boundary concomitant with the reduced ATB density. No obvious correlation between the SME and the grain size existed when the pre-deformation was rather lower (<4%). Larger grain size and less pre-existing martensite were conducive to realizing larger recovery strains.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Single Mn atom on nitrogen‐doped graphene (MnN4‐G) has exhibited good structural stability and high activity for the adsorption and dissociation of an O2 molecule, becoming a promising single‐atom ...catalyst (SAC) candidate for oxygen reduction reaction (ORR). However, the catalytic activity of MnN4‐G for the ORR and the optimal reaction pathway remain obscure. In this work, density‐functional theory calculations were employed to comprehensively investigate all the possible pathways and intermediate reactions of the ORR on MnN4‐G. The feasible active sites and the most stable adsorption configurations of the intermediates and transition states during the ORR were identified. Screened from all the possibilities, three optimal four‐electron O2 hydrogenation pathways with an ultralow energy barrier of 0.13 eV were discovered that are energetically more favorable than direct O2 dissociation pathways. Analysis of the free energy diagram further verified the thermodynamical feasibility of the three pathways. Thus, MnN4‐G possesses superior ORR activity. This study provides a fundamental understanding of the design of highly efficient SACs for the ORR.
Taking the indirect route: All the possible reaction pathways for oxygen reduction on single Mn atom anchored on nitrogen‐doped graphene including intermediates, H+ adsorption sites, and transition states have been investigated by DFT calculations. Four‐electron O2 hydrogenation pathways were found to be energetically more favorable than direct O2 dissociation pathways, with energy barriers as low as 0.13 eV.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
