Al4Ce Phase Research Articles

Effect of Al-5Ti-1B-xCe Refiner on Microstructure and Mechanical Properties of Cast Al-5Mg-3Zn-1Cu Alloys

The effects of Ce content on the microstructure and phase composition of the Al-5Ti-1B refiner and the refining effect of the Al-5Ti-1B-xCe (x = 0, 1, 5, 10 wt.%) refiner on the grain size, microstructure, and mechanical properties of Al-5Mg-3Zn-1Cu alloys were studied. The results show that the addition of 1.0 wt.% Ce in the Al-5Ti-1B refiner changes the TiAl3 phase from block to strip, and the massive Ti2Al20Ce phase is formed. When the Ce content of the Al-5Ti-1B refiner increases to 5.0 wt.%, the plate-like TiAl3 phase is surrounded by the Ti2Al20Ce phase, and the reticulate Al4Ce phase is formed. With the Ce content of the Al-5Ti-1B refiner further increasing to 10.0 wt.%, a lot of network distribution Al4Ce phase is formed. The volume of the Mg32(AlCuZn)49 phase of the as-cast Al-5Mg-3Zn-1Cu alloys is reduced after refining with the Al-5Ti-1B-xCe refiner. The Al-5Ti-1B-1Ce refiner has the best refining effect on as-cast Al-5Mg-3Zn-1Cu alloys, and the grain size of as-cast Al-5Mg-3Zn-1Cu alloys refined by the Al-5Ti-1B-1Ce refiner is reduced by 43% compared with as-cast Al-5Mg-3Zn-1Cu alloys refined by the Al-5Ti-1B refiner. Compared to the aged Al-5Mg-3Zn-1Cu alloys refined by the Al-5Ti-1B refiner, the yield strength, ultimate tensile strength, and fracture elongation of aged Al-5Mg-3Zn-1Cu alloys refined by the Al-5Ti-1B-5Ce refiner are improved by 4.0%, 4.6%, and 25.6%, respectively. Therefore, it can be seen that Al-5Ti-1B-1Ce refiner and Al-5Ti-1B-5Ce refiner have broad application prospects.

Nano cerium oxide addition enhancing the degradation resistance of biomedical Mg alloy produced by selective laser melting

Magnesium (Mg) alloys are one of the promising bone implant materials on account of their excellent biocompatibilities, suitable mechanical properties and a distinctive degradability. However, their clinical application is hindered by their too rapid degradation rate under physiological conditions. In this study, nano cerium oxide (CeO2) was incorporated into AZ61 (Mg–6Al–1Zn, wt.%) via selective laser melting to improve the degradation behavior. The results indicated that the degradation rate of AZ61 was slowed down by about 64%, with CeO2 containing up to 2 wt %. This was mainly attributed to: 1) in the selective laser melting process of AZ61-CeO2, a part of CeO2 was reduced to cerium (Ce), and Ce reacted with aluminum (Al) in AZ61 to form acicular Al4Ce phase and hinder island Mg17Al12 phase precipitation, which caused the reduction of galvanic corrosion; 2) the other part of CeO2 was uniformly dispersed in the Mg matrix. It could enter the degradation product film as the matrix degraded, which was conducive to increasing the relative density and positive charge quantity of the degradation product film, then improving the degradation product film resistance against corrosive solution penetration. Meanwhile, the compression strength of AZ61-CeO2 increased with increasing CeO2 content and reached the maximum value of 241 ± 12.0 MPa when CeO2 content was 2 wt%, which was principally put down to the refined crystalline strengthening and nano CeO2 dispersion strengthening. In addition, the results of cytocompatibility assessment showed that the AZ61-2CeO2 exhibited the best cytocompatibility. These results showed that the AZ61-2CeO2 produced by selective laser melting was a promising bone implant biomaterial.

Effect of Ce content on performance of AZ31 magnesium alloy anode in air battery

In this work, five AZ31-xCe magnesium alloy anode materials were prepared, and their microstructure, electrochemical properties and discharge properties were studied to reveal the effect of Ce content on the casting anode of magnesium air battery. The introduction of the Ce element can refine the grain and purify the α-Mg matrix. AZ31–1Ce magnesium alloy has the best corrosion resistance, and the activity of magnesium alloy enhances with the increase of Ce content. Compared with AZ31 magnesium alloy, AZ31-xCe magnesium alloy has higher discharge activity, which is due to the introduction of Ce element to purify the magnesium alloy, and the Al4Ce phase can promote the uniform dissolution of Mg matrix. When the discharge current density is 10 mA cm−2 the AZ31–4Ce anode shows the highest energy density of 1552.370 mWh g−1 and the best specific capacity of 1282.051 mAh g−1 which are 46.05% and 29.901% higher than the AZ31 anode. Compared with AZ31 magnesium alloy, the anode of AZ31–4Ce magnesium alloy has a smoother discharge surface morphology, which is beneficial to the desquamation of the discharge products.

Influence of cerium on the phase composition and crystallization behavior of cast aluminum alloys based on the Al—Mg—Si system

This study was conducted with calculations made in Thermo-Calc software (TCAl4.0 database) to find out the unexplored data on the phase composition, crystallization behavior of Al—Mg—Si—Ce alloys as regards the compositions of two-phase (Al) + Mg2Si cast aluminum-magnesium alloys. It was shown that (Al), Al4Ce, Mg2Si, Al8Mg5 phases may form during crystallization. At 4% Mg and (Si + Ce) concentrations of 1.5 %, a simultaneous increase in Ce and decrease in Si contents from 0.2 % and 1.3 % points promote consistent reactions L + (Al) + Al4Ce and L + (Al) + Al4Ce + Mg2Si. This suggests that the Al4Ce phase may hinder the growth of Mg2Si phase eutectic inclusions. Moreover, at 20 °C such a change in concentrations promotes a simultaneous decrease in the contents of Al4Ce and Al8Mg5 phases, along with a decrease in the amount of magnesium silicide. While adding Ce in the Al—4%Ce—0.5%Si alloy, the fraction of Mg2Si is approximately constant throughout the entire crystallization range (1.34 %), but each 0.1% Ce increases the Ce-bearing intermetallic fraction by 0.17 %, and at 0.7 % Ce the proportions of two phases are equal. When studying the phase composition at representative annealing temperatures of 400 и 550 °C, it was revealed that the (Al) solid solution becomes supersaturated as a result of Al8Mg5 phase dissolving. Each 0.1% Ce increases the Mg content in the (Al) solid solution by 0.005 % in the first case and by 0.01 % in the second one. This indicates a potentially positive influence of Ce on matrix strengthening. Based on the results, it was concluded that it is advisable to add Ce in an amount of up to 0.7 %, which slightly reduces the liquidus temperature (to ~636+638 °C), but reduces the non-equilibrium solidus temperature by ~30 °C to 421 °C. At the same time, at a constant Mg2Si phase formation temperature (581 °C), the eutectic crystallization range (Al)+Al4Ce expands with Ce addition, which can compensate for the decrease in casting properties. The Al—4%Ce—0.5%Si—0.7% Ce alloy has the following phase composition: Al4Ce 1.19 %, the [Mg2Si/Al4Ce] ratio = 0.89, Al8Mg5 fraction is 7.92 % at 20 °C, Mg concentrations in the (Al) solid solution are 3.22 % and 3.36 % at temperatures of 400 °C and 550 °C, respectively. The presented results serve as the basis for subsequent experiments and justify compositions and temperature conditions for obtaining cast aluminum-magnesium alloys with cerium having a modifying effect on Mg2Si eutectic inclusions.

Effect of Hot Forging Process Parameters and Ce Addition on the Microstructure and Mechanical Properties of an As‐Forged AZ80 Alloy

Herein, Mg–8Al–0.5Zn (AZ80) alloys with different Ce contents (0, 0.2, 0.8, and 1.4 wt%) are designed and prepared. The effects of the forging temperature (250, 300, 350, 400, and 450 °C), forging reduction (7.5%, 17.5%, 27.5%, and 37.5%), and Ce addition on the microstructure and compressive properties of the as‐forged AZ80 alloy are investigated. With increasing forging temperature, the compressive strength and fracture strain increased due to grain refinement. With an increase in forging reduction, the yield strength and compressive strength were also improved under the action of fine‐grain strengthening and work hardening. The results finally reveal that the appropriate forging temperature was 400 °C, and the optimized forging reduction was 27.5%. The addition of Ce significantly refined the grains of the as‐forged AZ80 alloys, and with addition of 1.4 wt% Ce, the grain size was significantly reduced by ≈42.0%. AZ80 alloys with Ce addition obtain remarkable grain refinement effects due to the existence of the Al4Ce phase. The results of tensile tests show that Ce addition effectively improves the tensile properties ascribed to the excellent grain refinement and work hardening effect.

Island-to-acicular alteration of second phase enhances the degradation resistance of biomedical AZ61 alloy

Abstract The application of Mg–6Al–1Zn (wt.%, AZ61) alloy as biodegradable bone implant material is limited due to its too rapid degradation, which is largely related to the microgalvanic corrosion induced by the coarse island second phase in the alloy. In this study, cerium (Ce) was alloyed in AZ61 alloy by selective laser melting, aiming to enhance its degradation resistance. The microstructure characteristics were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The degradation behavior was studied by the electrochemical test and weight loss test. Besides, the mechanical properties and cytocompatibility of the alloy were also assessed. The results showed that Al preferentially reacted with Ce in the AZ61-Ce alloy because of the high electronegativity difference between Al and Ce and formed acicular Al4Ce phase due to the oriented crystal growth. Meanwhile, the consumption of Al in forming Al4Ce phase inevitably reduced the precipitation of island Mg17Al12 phase. Compared with island Mg17Al12 phase, the acicular Al4Ce phase possessed much larger ratio of length to the cross-sectional area, leading to a higher electrical resistance. As a consequence, the island-to-acicular alteration of second phase greatly decreased the corrosion current density, thereby enhancing the degradation resistance by about 7 times. In addition, the AZ61-Ce alloy presented improved compressive strength owing to the strengthening effect of the acicular second phase, as well as favorable biocompatibility. The island-to-acicular alteration of second phase may provide a method for the development of high performance biomedical Mg alloys.

Effect of Ce Addition on Modifying the Microstructure and Achieving a High Elongation with a Relatively High Strength of As-Extruded AZ80 Magnesium Alloy.

Forming magnesium alloys with rare earth elements (La, Gd, Nd, Y, Ce) is a routine method for modifying their microstructure and properties. In the present work, the effect of Ce addition on the microstructure evolution and the mechanical properties of as-extruded Mg-8Al-0.5Zn (AZ80) alloy was investigated. All of the extruded AZ80-xCe (x = 0, 0.2, 0.8 and 1.4 wt %) alloys exhibited equiaxed grains formed by fully dynamic recrystallization, and the grain size of the extruded AZ80 alloy was remarkably reduced by ~56.7% with the addition of 1.4 wt % Ce. Furthermore, the bulk-shaped Al4Ce phase formed when Ce was first added, with the Ce content rising to 0.8 wt % or higher, and Al4Ce particles in both the nano- and micron sizees were well distributed in the primary α-Mg matrix. The area fraction of the Al4Ce particles expanded with increasing Ce content, providing more nuclei for dynamic recrystallization, which could contribute to the grain refinement. The results of the tensile tests in this study showed that Ce addition effectively improved the room temperature formability of the as-extruded AZ80 alloy, without sacrificing strength. The significantly improved mechanical properties were ascribed to excellent grain refinement, weakened texture strength, an increased Schmid factor, and a reduced area fraction of low-angle grain boundaries, all resulting from Ce addition to the as-extruded AZ80 alloy. The contribution of the nano-Al4Ce precipitates on improving the mechanical properties was also discussed in this paper.

Cerium Addition Improved the Dry Sliding Wear Resistance of Surface Welding AZ91 Alloy.

In this study, the effects of cerium (Ce) addition on the friction and wear properties of surface welding AZ91 magnesium alloys were evaluated by pin-on-disk dry sliding friction and wear tests at normal temperature. The results show that both the friction coefficient and wear rate of surfacing magnesium alloys decreased with the decrease in load and increase in sliding speed. The surfacing AZ91 alloy with 1.5% Ce had the lowest friction coefficient and wear rate. The alloy without Ce had the worst wear resistance, mainly because it contained a lot of irregularly shaped and coarse β-Mg17Al12 phases. During friction, the β phase readily caused stress concentration and thus formed cracks at the interface between β phase and α-Mg matrix. The addition of Ce reduced the size and amount of Mg17Al12, while generating Al4Ce phase with a higher thermal stability. The Al-Ce phase could hinder the grain-boundary sliding and migration and reduced the degree of plastic deformation of subsurface metal. Scanning electron microscopy observation showed that the surfacing AZ91 alloy with 1.5% Ce had a total of four types of wear mechanism: abrasion, oxidation, and severe plastic deformation were the primary mechanisms; delamination was the secondary mechanism.

Combined effects of cerium and cooling rate on microstructure and mechanical properties of AZ91 magnesium alloy

The specimens of AZ91–xCe(x = 0, 0.3, 0.6, 0.9, 1.2, mass fraction wt%) with different thicknesses were prepared by die casting process, their as-cast microstructure and room temperature mechanical properties were investigated to analyze the change rule of microstructure and mechanical properties of AZ91 magnesium alloy under combined effects of cooling rate and cerium content. The results show that, the microstructure and mechanical properties of AZ91 magnesium alloy were twofold influenced by cooling rate and cerium content. With the increase of cooling rate and Ce content, the average as-cast grain size is evidently refined; the amount of β-Mg17Al12 decreases and distribution becomes discrete. While decreasing cooling rate or increasing Ce content, Al4Ce phase is more and the morphology tends to strip and needle from granular and short rod-like. The tensile strength and elongation of AZ91–xCe magnesium alloy are improved with increasing cooling rate. With the increase of Ce content, the tensile strength and elongation of AZ91–xCe magnesium alloy increased first and decreased afterwards, besides the action of Ce to improve tensile strength and elongation is more evident under faster cooling rate. Mechanical properties of samples are optimal in this work, when Ce content is 0.96% and cooling rate is 39.6 K s−1, tensile strength (259.7 MPa) and elongation (5.5%) are reached maximum, respectively.

Effects of cerium on as-cast microstructure of AZ91 magnesium alloy under different solidification rates

In order to research the different effects of Ce on as-cast microstructure of AZ91 magnesium alloy under different solidification rates, the die-cast samples with different diameters and different Ce contents were prepared, and some characteristics of as-cast microstructure were analyzed. The results showed that Ce could refine grain size, decrease the fraction of eutectic β-Mg17Al12 phase, form Al4Ce phase and decrease solid solution of Al in the α-Mg matrix, but the above behaviors of Ce would be weakened under higher solidification rate. The essential reason for Ce to affect as-cast microstructure was that the Ce and Al concentrated in the liquid phase in front of solid/liquid interface during solidification because Ce itself is difficult to solid solute in α-Mg matrix and inhibits solid solution of Al in α-Mg matrix. However, the dynamic condition of concentration of Ce, Al would be changed when solidification rate varied, resulting in different influence extents of Ce on as-cast microstructure under different solidification rates.

Effect of cerium addition on corrosion behaviour of AZ61 + XCe alloy under salt spray test

The corrosion behaviour of Mg–6Al–1Zn+XCe (where X=0.5, 1.0, 1.5 and 2.0wt% Ce) alloys, aged for 18h at different temperatures of 180°C, 200°C, 220°C and 240°C, was studied in 3.5wt% NaCl solution. The salt spray test was conducted in accordance with ASTM-B117 standard (fog test). The corrosion morphologies, corrosion rate and the composition of the corrosion products were investigated by X-ray Diffraction (XRD), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) techniques. The results show the cerium addition and ageing treatment has significantly influenced the corrosion morphologies and the corrosion rate. In AZ61 alloy, the intermetallic β (Mg17Al12) phase acts as a corrosion barrier and upon ageing the Al4Ce phase precipitates along the α grain boundaries. The precipitation modifies the β phase to form more continuous network which subsequently reduces the corrosion attack in the chlorine environment. Salt spray test result shows the AZ61 alloy with 1.5wt% Ce aged at 220°C exhibits the better corrosion resistance.

Electronic and elastic properties of Al4Ce binary compound under pressure via first-principles

In this paper, the effects of pressure on the structural, electronic and mechanical properties of tetragonal Al4Ce phase have been analyzed by means of first-principles method based on the density functional theory within generalized gradient approximation (GGA). The calculated equilibrium lattice parameters under zero pressure are in good agreement with the previous experimental and other theoretical data. The obtained total density of state (TDOS) and partial density of states (PDOS) of Al4Ce at varying pressures indicate that this compound exhibits favorable metallic behavior. In addition, the isotropic bulk modulus B, shear modulus G, Young modulus E and Poisson’ ratio υ of Al4Ce at different pressures are investigated by using the Voigt–Reuss–Hill averaging scheme. The results demonstrate that Al4Ce phase is ductile according to the analysis of BH/GH and has good mechanical stability. Finally, the Debye temperatures (ΘD), which is also obtained from the elastic constants, increases with increasing pressure.

Glass formation and phase selection of melt-spun Al–Zn–Ce alloys

The glass-formation characteristics and phase-selection behavior of Al–Zn–Ce alloys have been studied by X-ray diffraction (XRD) and different scanning calorimetry (DSC). As the concentration of Ce increases, an intermetallic compound Al2Zn2Ce appears, which prevents the occurrence of phase separation, and improves the forming ability of the single amorphous phase. In Al83Zn10Ce7 alloys, the precipitation of fcc-Al was accompanied with the Al2Zn2Ce phase and Al4Ce phase. Moreover, the presence of fcc-Al appears to favor the nucleation and growth of the Al2Zn2Ce and Al4Ce phase. However, it seems that the Al2Zn2Ce and Al4Ce nucleate competitively with the fcc-Al phase and the growth of fcc-Al and Al2Zn2Ce prefers to that of Al4Ce. The competitive nucleation and growth limitation of the various phases are favorable to the formation of Al–Zn–Ce amorphous alloys. For the amorphous Al–Zn–Ce alloys, the glass formation is not controlled by nucleation restrictions but largely by the suppression of growth of nuclei formed during rapid melt quenching.

Effect of Cerium Addition on the Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloy

Al–8.6Zn–2.6Mg-2.4Cu–xCe(x = 0–0.4 wt. %) alloys were prepared by metal mould casting method, the effects of Ce on the microstructure and mechanical properties of the alloys were investigated. The results showed that the dendrite as well as grain size were refined by the addition of Ce, and the best refinement was obtained in 0.25 wt % Ce containing alloy. The main phases in the as-cast alloys were α-Al, Mg-Zn32, Mg32 (Al, Zn)49, and Al4Ce phase was found in the alloys containing more than 0.1%Ce. The addition of Ce improved the mechanical properties of the alloys. The strengthening mechanism was attributed to grain refinement and compound reinforced

Effects of cerium on the microstructure and mechanical properties of Mg–20Zn–8Al alloy

Mg–20Zn–8Al– xCe( x = 0–2 wt.%) alloys were prepared by metal mould casting method, the effects of Ce on the microstructure and mechanical properties of the alloys were investigated. The results showed that the dendrite as well as grain size were refined by the addition of Ce, and the best refinement was obtained in 1.39% Ce containing alloy. The main phases in the as-cast alloys were α-Mg and τ-Mg 32(Al, Zn) 49, and Al 4Ce phase was found in the alloys contained more than 1.39% Ce. The addition of Ce improved the mechanical properties of the alloys. The strengthening mechanism was attributed to grain refinement and compound reinforced.

Ａｌ‐Ｆｅ‐Ｃｅ合金の急冷凝固組織と相分解

Al-0.5 to 4mass%Ce, Al-1 mass%Fe-0.5mass%Ce and Al-4mass%Fe-4mass%Ce alloys were rapidly solidified into a ribbon shape at 105 and 106K/s by a single roller technique. The solid solubility of Ce in aluminum cooled at 106K/s extends up to about 0.5mass%. A spherical metastable phase which probably has f.c.c. structure a=0.828nm is observed in the ribbons containing Ce 1 to 4mass%. Coarse spherical particles and cell structures form at a cooling rate about 105K/s. The spherical particles and cell boundary intermetallic compounds have an orthorhombic structure with a stoichiometry corresponding to the equilibrium Al4Ce phase. Al-4mass%Fe-4mass%Ce alloys solidified at 106K/s contain fine particles of Al-Ce metastable phase. When these alloys and the alloy containing supersaturated solid solution are heated at 673K for 3.6ks, a plate shaped Al-Fe-Ce metastable phase precipitates in the <100> direction of the matrix. This phase probably has a cubic structure with an unit cell parameter a=0.410nm. Al-Fe-Ce metastable phase precipitated in the α-cell and the cell boundary intermetallic compound in the alloy cooled at 105K/s have a tetragonal structure with a stoichiometry corresponding to the equilibrium Al8CeFe4 phase.

急冷凝固したＡｌ‐Ｃｕ合金の組織と相分解

Al-0.5 to 4mass%Ce, Al-1 mass%Fe-0.5mass%Ce and Al-4mass%Fe-4mass%Ce alloys were rapidly solidified into a ribbon shape at 105 and 106K/s by a single roller technique. The solid solubility of Ce in aluminum cooled at 106K/s extends up to about 0.5mass%. A spherical metastable phase which probably has f.c.c. structure a=0.828nm is observed in the ribbons containing Ce 1 to 4mass%. Coarse spherical particles and cell structures form at a cooling rate about 105K/s. The spherical particles and cell boundary intermetallic compounds have an orthorhombic structure with a stoichiometry corresponding to the equilibrium Al4Ce phase. Al-4mass%Fe-4mass%Ce alloys solidified at 106K/s contain fine particles of Al-Ce metastable phase. When these alloys and the alloy containing supersaturated solid solution are heated at 673K for 3.6ks, a plate shaped Al-Fe-Ce metastable phase precipitates in the direction of the matrix. This phase probably has a cubic structure with an unit cell parameter a=0.410nm. Al-Fe-Ce metastable phase precipitated in the α-cell and the cell boundary intermetallic compound in the alloy cooled at 105K/s have a tetragonal structure with a stoichiometry corresponding to the equilibrium Al8CeFe4 phase.