To further strengthen the AlCoCrFeNi high-entropy alloy (HEA) coating prepared by high-speed laser cladding (HLC), laser remelting (LR) was chosen to reprocess it. The effects of LR on the ...topography, microstructure, growth orientation, phase distribution, and properties were investigated. It was revealed that there were a large number of liquid phase separation (LPS) zones in the HLC coating because of an ultrafast cooling rate. After LR, the LPS zones were eliminated. Compared to HLC coating, the microhardness increased from 622 HV to 762 HV, and the friction coefficient and the wear weight loss were reduced by 0.1 and 0.5 mg, respectively. In electrochemical testing, the self-corrosion potential increased by 45.9 mV and the self-corrosion current density decreased by one order of magnitude. Meanwhile, EBSD analysis indicated that the LPS zones were prone to recrystallization. The LPS zones were nickel-poor, low hardness, also BCC phase, and had a clearer (101) orientation. With the elimination of the LPS zones, the kernel average misorientation values were reduced, Taylor factor values and high angle grain boundaries were increased, and the average grain size was reduced from 2.43 μm to 2.12 μm. Eventually, for LR coatings, the combination of fine grain strengthening, solid solution strengthening, spalling reduction, and Cr element segregation resulted in better wear and corrosion resistances. The overall results show that a reasonable LR application can induce the microstructure of the HLC coating and improve its service properties.
● The AlCoCrFeNi high-entropy alloy coatings were prepared by high-speed laser cladding (HLC) and reprocessed by laser remelting (LR).● There were a large number of liquid phase separation (LPS) zones in the HLC coating. After LR, the LPS zones were replaced by fine equiaxed crystals.● The LPS zones were nickel-poor and low hardness, had a clearer (101) orientation, and tended to spall off in the wear test, causing a decrease in the overall wear resistance of the coating.● As a result of the elimination of the LPS zones, the microhardness and wear resistance of the LR coating were improved by solid solution strengthening and fine grain strengthening.● Appropriate undercooling and more high angle grain boundaries caused by LR provided a larger driving force for grain boundary segregation. The elemental content of Cr at the grain boundaries became higher, and the corrosion resistance of the LR coatings increased significantly. Display omitted
•HLC led to a large number of the LPS zones in the AlCoCrFeNi HEA coating.•LR could successfully eliminate the LPS zones.•Recrystallization made the grains of the LPS zones coarse and soft.•The microhardness and wear resistance of the coating were improved by LR.•Higher Cr content at grain boundaries boosted corrosion resistance of LR coating.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The initial microscopic reaction process of aluminum hydrolysis is explained.•Explains the disappearance of hydrogen at high temperatures.•Outer-layer aluminum atoms preferentially ...react with oxygen atoms to form Al2O3, while inner-layer aluminum atoms are more inclined to combine with hydrogen atoms to form AlH3.•The structure was observed to have an outer layer of Al2O3 intercalated with AlH3 and an inner layer of AlH3.•Explaining the effect of electric fields on the rate of hydrogen production from aluminum hydrolysis.
Hydrogen energy is gaining attention as a non-polluting source. Aluminum’s reaction with water for propulsion and hydrogen production is widely used, but its nanoscale characteristics are unexplored. This study investigated aluminum hydrolysis in water vapor by ReaxFF-MD, examining effects of temperature and electric field. The oxidation of the aluminum surface is accompanied by aluminum dissolution, hydrogen generation and H3O+ formation, Formed hydrides and oxides were AlH3 and Al2O3. Hydrogen disappearance at 700 K and 900 K was due to conversion to AlH3. The diffusion of hydrogen and oxygen atoms in the Z direction was enhanced at increasing temperatures, Outer aluminum atoms preferentially reacted with oxygen to form Al2O3, while inner atoms reacted with hydrogen to form AlH3, the loosely packed outer oxide layer contains inclusions of AlH3. Studies at room temperature under different electric fields showed −Z field promoted the reaction while + Z field inhibited it, attributed to different electric field strengths’ effect on OH– ion electron-sharing Coulomb equilibrium, resulting in varying rates of hydroxide polar covalent bond cleavage. Our results clarify the atomic-scale effects of temperature and electric field on the aluminum-water reaction, providing guidance for optimizing experimental conditions and enhancing the efficiency of hydrogen production.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The initial temperature is positively correlated with the diffusion coefficient.•The solid–liquid transition time of the system is affected by the cooling rate.•The lower the cooling ...rate, the easier the crystal structure formation.•The RDF analysis results are consistent with the visualization results.
To analyze the various factors affecting the solidification organization of Al-Cu alloys, the melting and solidification processes of Al0.67Cu0.33 alloy were simulated by the embedded atomic method (EAM) potential. It is found that the diffusion coefficient of the system keeps rising with the increasing initial temperature and relaxation time. It is a positive correlation between initial temperature, relaxation time and diffusion coefficient. The RDF analysis results are shown that as the cooling rate decreases, the crystal content of the solidified tissue increases and crystal structure characteristics of the system become more obvious. At the cooling rate of 1 × 1010 K/s, the percentage of system crystal compositions reaches 78.4%. The system shows obvious crystal structure characteristics. However, when the cooling rate was 1 × 1014 K/s, the crystalline content of the system is only 0.3% and shows obvious non-crystalline characteristics. It provides a theoretical basis for improving the properties and optimizing the microstructure of Al-Cu alloy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Mg promotes the atomic diffusion of Al-Cu-Mg alloy.•The addition of Mg causes the alloy to generate more large-size Cu clusters.•The introduction of Mg lead to the formation of more ...FCC phases.•The enrichment of Cu intensified with the increase of Mg content.•Verified the consistency of simulation and experimental results.
To analyze the mechanism of the Mg content on Cu precipitation in Al-Cu-Mg ternary alloy, the microstructure evolution of Al-5%Cu, Al-5%Cu-1%Mg and Al-5%Cu-2%Mg alloys during the solidification process was investigated by both the molecular dynamics simulation and solidification experiment methods. The simulated results demonstrate that the introduction of Mg accelerates atomic diffusion. And as the Mg content increases, more large-sized Cu agglomerates are formed in the solidified tissue, due to the Mg plays a connecting role in the process of Cu agglomerate formation. It is also found that the introduction of Mg results in the development of more FCC phases in the final tissue. The experimental results show that Cu elements are concentrated in the Al crystal boundaries, and the degree of Cu enrichment increases with the level of Mg content. The physical phase analysis shows that the final organization is primarily composed of the Al phase and Al2Cu phase, and both phases increase slightly with a higher Mg rate. The consistency between experimental and simulation results was verified by a comparative discussion of the Cu agglomerated and precipitated phases. It provides a theoretical basis for improving Al-Cu-Mg alloys' performance enhancement and structural optimization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The AlCoCrFeNi high-entropy alloy coatings were prepared by laser cladding (LC) and reprocessed by laser remelting (LR). Laser remelting caused cracks on the coating surface, but the cracks of ...boronized laser remelting (LR-B) coating were significantly suppressed. Compared to the LR coating, the microhardness of the LR-B coating increased from 643 HV to 1008 HV, the friction coefficient decreased from 0.55 to 0.45, and the self-corrosion potential increased by 134 mV. The crack elimination contributed to the transition of 25% of the BCC phase to the FCC phase. The property enhancement was mainly due to the fine grain strengthening, dislocation strengthening, and Cr2B reinforced particles as reinforced phase.
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•A trace amount of boron was doped in the protective gas during laser remelting.•The cracks of the boronized laser remelting (LR-B) coating were significantly suppressed.•With the addition of boron, the FCC phase and Cr2B were formed.•The Cr2B second-phase strengthening increased microhardness and wear resistance.•The Cr2B particles in the LR-B coating resulted in excellent corrosion resistance.
To avoid cracking of the AlCoCrFeNi high-entropy alloy (HEA) coating during laser remelting (LR), a trace amount of boron (B) was doped in the protective gas. Compared to the LR coating, the cracks of the boronized laser remelting (LR-B) coating were significantly suppressed, the microhardness increased from 643 HV to 1008 HV, the friction coefficient decreased from 0.55 to 0.45, and the self-corrosion potential increased by 134 mV. The crack elimination mainly contributed to the transition of 25 % of the BCC phase to the FCC phase, and the property enhancement was due to the fine grain strengthening, dislocation strengthening, and Cr2B reinforced particles generation. This novel finding can be applied to other BCC structure HEA coatings for macroscopic crack control and optimization of wear and corrosion resistances.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The performance of Al-0.1Sn-0.1In-0.05Ga alloys as anodes for Al–air batteries is investigated for low carbon development needs. Low melting point elemental metals were added to high purity Al ...(99.9999 %) using micro alloying, either in a diffuse distribution or as a second phase, depending on their solid solubility in the Al. The correlation between the microstructure and electrochemical properties of Al-0.1Sn-0.1In-0.05Ga alloys was established. The experiments were conducted in a 4.0 mol/l NaOH solution. The electrochemical characteristics of the Al-0.1Sn-0.1In-0.05Ga anodes were assessed by using potentiodynamic polarization, electrochemical impedance spectroscopy, and galvanostatic discharge experiments. It is indicated that the inclusion of Sn, In, and Ga elements results in improved corrosion resistance and discharge activity in the anode composed of Al. This can be attributed to the presence of nano-scale second phase particles and a uniform microstructure in the Al-0.1Sn-0.1In-0.05Ga alloy, which effectively inhibits localized crystallographic corrosion. In comparison to pure Al, the Al-0.1Sn-0.1In-0.05Ga alloy exhibits a reduction in corrosion current density by 24.77 % and an increase in anode efficiency by 40 %. When discharged at a current density of 10 mA/cm2, an Al–air battery with an Al-0.1Sn-0.1In-0.05Ga anode exhibits a discharge voltage of 1.523 V, a discharge capacity of 2214 Ah/kg, and an anode efficiency of 74.31 %. The research has the potential to advance Al–air batteries' progress and significantly contribute to global sustainability efforts.
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•The anode efficiency of Al-0.1Sn-0.1In-0.05Ga prepared by the microalloying reaches 74.31 %.•The HER of Al-0.1Sn-0.1In-0.05Ga alloy is 50 % lower compared to pure Al.•The alloy Al-0.1Sn-0.1In-0.05Ga contains a nanoscale phase that is rich in both In and Sn elements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
