Al Ca Alloy Research Articles

Metallothermic reduction of Sc2O3 using Al–Ca alloys equilibrated with CaO–CaCl2 flux

Through a fundamental study, the mechanism of metallothermic reduction of Sc2O3 in a CaO–CaCl2 flux system was determined via a thermochemical equilibrium method, aiming to produce an Al–Sc–Ca alloy (Sc: ∼0.5–3.6 wt%; Ca: ∼0.8–1.8 wt%) at 1273–1623 K. The effect of the oxygen potential on Sc reduction was investigated to establish a general mechanism of Sc reduction. The effect of the CaO activity on the flux and content of Ca in the alloy was evaluated to confirm the role of Ca in the mechanism of metallothermic CaScO2.5 reduction.Under CaO-saturated flux, the Sc recovery increased significantly. The oxygen potential established by the Ca–CaO equilibrium was the driving force for enhanced Sc recovery. The Sc recovery was positively correlated with the excess Ca (amount of Ca oxidized directly to CaO) in the alloy. The enthalpy and entropy of the metallothermic reduction were calculated from the temperature-dependence of the equilibrium constant using the van't Hoff equation. The equilibrium constant decreased with increasing temperature, indicating that the reaction is exothermic. An Al–Sc alloy with a maximum Sc content of 3.98 % was obtained via metallothermic reduction. The formation of the desired Al3Sc compound was verified using X-ray diffraction. The uniform distribution of Sc in the alloy and faceted morphology of Al3Sc were confirmed by scanning electron microscopy (SEM) and electron probe micro-analysis (EPMA).

Convert Harm into Benefit: The Role of the Al10CaFe2 Phase in Al-Ca Wrought Aluminum Alloys Having High Compatibility with Fe

The compatibility of the wrought Al-Ca alloy with the element Fe was investigated in the present study. In this work, both the Al-Ca alloy and Al-Ca-Fe alloy were synthesized through melting, casting, heat treatment, and rolling. A new ternary Al-Ca-Fe eutectic phase, identified as Al10CaFe2 with an orthorhombic structure, demonstrated enhanced performance, as revealed by nanoindentation tests. Combining the results of the nanoindentation and EBSD, it can be inferred that during the rolling and heat treatment process, the divorced eutectic phases were broken and spheroidized, and the structure of the Fe-rich alloy became finer, which promotes the formation of fine grains during the process of dynamic recrystallization and effectively hindered the grain growth during thermal treatment. Consequently, the strength of the as-rolled Al-Ca alloy was improved with the addition of 1 wt.% Fe while the ductility of the alloy was maintained. Therefore, adding Ca into the high-Fe content recycled aluminum altered the form of the Fe-containing phases in the alloy, effectively expanding the application scope of recycled aluminum alloy manufacturing. This approach also offered a method for strengthening the Al-Ca aluminum alloys. Compared to the traditional approach of reducing Fe content in alloys through metallurgical means, this study opened a new avenue for designing novel, renewable aluminum alloys highly compatible with impurity iron in scrap.

The Effect of Cooling Rate on the Microstructure and Physical Properties of Hypereutectic Al–Ce Alloys

The Effect of Cooling Rate on the Microstructure and Physical Properties of Hypereutectic Al–Ce Alloys

Additive manufacturing of a lightweight Al-Ca alloy by direct energy deposition and laser powder bed fusion

Abstract High strength and low density materials are needed to achieve lightweight design of components. Aluminum base metals alloyed with calcium are of potential interest because of the low density of calcium and its abundance. The additive manufacturing of dense and crack free samples out of an Al-10 wt.% Ca (Al-10Ca) alloy is presented. Both laser-based direct energy deposition (DED-LB) and laser powder bed fusion (LPBF) processes were applied to manufacture sample material. Preheating of the substrate plate is needed in LPBF to receive crack free samples. An analysis of the microstructure shows an Al-Al4Ca lamellar eutectic.

Influence of Al and Ca on the Ductility of Mg–Al–Ca Alloys

Magnesium and its alloys offer huge potential for lightweight applications. However, many Mg alloys suffer from limited room‐temperature formability. It has previously been shown that the addition of aluminium and calcium to Mg can improve ductility. Therefore, in the present work, it is aimed to systematically vary the alloying content of Al and Ca and to study their effects on the slip system activity and crystallographic texture after rolling and recrystallization. In the results, it is shown that all investigated ternary alloys in the range of 1–2 wt% Al and 0.005–0.5 wt% Ca have an increased ductility (in the range of 10–17% increase compared to pure Mg), whereas the binary Mg–Al and Mg–Ca alloys suffer from limited ductility (10% tensile elongation) and strength (175 MPa ultimate tensile strength). Non‐basal and especially <c + a>‐slip is active in all compositions (in 15–33% of the grains examined). Basal‐type textures are observed for all compositions, but with significantly weaker basal peak intensities for Ca‐containing samples when compared to pure Mg. The combination of activation of the <c + a> slip system and texture weakening is discussed as being responsible for the improved ductility of the ternary Mg–Al–Ca alloys.

Substituting Ce with La and Nd in Al11Ce3: Effect on microstructure and mechanical properties

Microstructure and mechanical properties are studied for five cast, coarse-grained intermetallic alloys: binary Al11Ce3 and Al11La3, ternary Al11(Ce0.75La0.25)3 and Al11(Ce0.5La0.5)3, and quaternary Al11(Ce0.54La0.27Nd0.19)3 with mischmetal composition. All compounds exhibit a single phase indicating a solid solution among the three rare-earth elements (RE=Ce, La, and Nd) on the Ce sublattice of Al11RE3, in disagreement with Thermo-Calc prediction of segregation of Ce and (La, Nd) into two insoluble compounds. The lattice parameters of this orthorhombic Immm-structured α-Al11RE3 phase increase as La concentration increases, while the α-β phase transformation temperature decreases. The five Al11RE3 compounds show very similar (i) propensity for twinning, (ii) high hardness (4.1–4.3 GPa), and (iii) low indentation fracture toughness (0.48–0.65 MPa m1/2). The Al-Al11RE3 interface lattice mismatches, as calculated for two stable interface orientations, have comparable values across all examined compounds. These similarities imply that these Al11RE3 compounds will exhibit comparable strengthening and coarsening resistance in Al-RE-based eutectic alloys, thus positioning them as economically- and environmentally-favorable alternatives to the well-developed binary Al11Ce3 compound formed in current eutectic Al-Ce alloys.

Creep property and microstructural evolution of laser powder bed fused binary Al–10Ce alloy

Aluminum–Cerium (Al–Ce) based alloys have shown promise as cost-efficient high temperature creep-resistant aluminum alloy. These alloys are also highly printable with laser powder bed fusion (LPBF) additive manufacturing. This study investigates the creep property of a near eutectic binary Al–10Ce (wt. %) alloy manufactured by LPBF and its microstructural evolution during creep. The as-built alloy exhibited columnar grain structure with a weak cube texture and its microstructure consisted of fine eutectic Al + Al11Ce3. Compressive creep tests with incremental stresses were performed perpendicular to the build direction at temperatures ranging from 275 to 400 °C. The stress exponent was approximately 1 in the low stress regime and 5–7 in the high stress regime, corresponding to diffusion and dislocation creep, respectively. The average activation energy was approximately 229 kJ/mol·K in the temperature between 275 and 375 °C. After creep deformation, the melt pool boundary faded and the eutectic Al11Ce3 intermetallics slightly coarsened. The grain structure remained relatively stable and the grain boundary became more pronounced. By comparing the minimum creep strain rate to other alloys, it was found that LPBF Al–10Ce is more creep resistant than similar cast binary Al–Ce counterpart, some ternary Al–Ce alloys and LPBF AlSi10Mg alloy. This benchmark results on the creep property of LPBF binary eutectic Al–Ce alloy provide insights to future development of creep-resistant Al–Ce alloys.

Modified embedded atom method interatomic potential for FCC γ-cerium

As interest in Cerium containing alloys and Al-Ce alloys in particular grows, the need to generate predictions of mechanical, thermodynamic and transport properties across a compositional space becomes more pronounced. The absence of a reliable interaction potential to be used in classical molecular dynamics (MD) simulation of γ-Ce is a fundamental bottleneck to subsequent alloy simulation. In this work, a Modified Embedded Atom Method (MEAM) potential to be used in MD simulation for γ-Ce has been generated. The parameterization process involved two steps. First, the iterative Latin hypercube sampling (LHS) method was used to generate MEAM parameter sets based on an automated optimization of energies and forces relative to a training set of small configurations evaluated through Density Functional Theory (DFT). Second, a human-guided optimization in that local parameter space was performed to refine the parameters to satisfy an array of mechanical, thermodynamic and transport properties available from the experimental literature. When used in an MD simulation, the resulting potential provides excellent estimates of all tested material properties across a broad temperature range. This γ-Ce potential, when combined with existing MEAM potential for Al, will form the necessary foundation for the subsequent development of a mixture potential, enabling the simulation of Al-Ce and Al-Ce-X alloys.

The Characterization of Coatings Formed on As-Cast Al, Al–Si, and Al–Ca Aluminum Substrates by Plasma Electrolytic Oxidation

In this study, ceramic coatings were grown on the surface of as-cast aluminum alloys via plasma electrolytic oxidation (PEO). The effect of the Si- and Ca-alloying elements in aluminum on the growth process, morphology, composition, mechanical, and corrosion properties of the PEO coatings was investigated. Uniform coatings with a minimum number of defects were formed on the surfaces of Al–Ca alloys. Increasing the Si content in Al led to an increase in the bulk and surface porosity of the coatings. The α-Al2O3 phase mainly formed in the coatings synthesized on pure Al and Al–Ca alloys, while an increased amount of Si in Al alloys hindered the formation of the α-Al2O3 phase. The coatings had a microhardness of 660–1180 HV, which was 20–30 times higher than that of the original as-cast alloy. Moreover, the coating on the Al–Ca alloys had the highest peak hardness, which was probably caused by the formation of a greater amount of the α-Al2O3 phase. Electrochemical studies in 3.5% NaCl have shown that PEO coatings reduce the corrosion current density. Of all PEO-treated alloys, Al and Al1Ca have the lowest corrosion current density and hence the highest corrosion resistance due to the composition and uniformity of the coating.

Effect of Fe additions on microstructure and mechanical properties in near-eutectic Al–Ce alloys

The effects of adding 1 or 3 wt % Fe to a near-eutectic Al–10Ce alloy are investigated in terms of their as-cast and aged microstructures, thermal stability, and creep resistance. A 1 wt% Fe addition forms fine, Chinese-script Al10CeFe2 and Al11Ce3 eutectic phases without loss of microhardness as compared to the Fe-free Al–10Ce alloy, unlike in traditional cast Al-alloys where detrimental coarse phases are observed when adding Fe. Adding 3 wt% Fe increases hardness significantly while forming primary Al10CeFe2 in a coarse rod morphology. These near-eutectic Al–10Ce–1Fe and hyper-eutectic Al–10Ce–3Fe alloys, after thermal exposure at 400 and 425 °C for up to 384 h, show only a small loss in microhardness, indicating excellent coarsening resistance. Compressive creep measurements performed at 300 °C show similar trends: (i) near-eutectic Al–10Ce–1Fe performs quite similarly to near-eutectic Al–10Ce and (ii) hyper-eutectic Al–10Ce–3Fe exhibits much improved creep resistance, similar to near-eutectic Al–10Ce–5Ni with costly Ni additions, and much better than hyper-eutectic Al–13Ce. After surface laser remelting to simulate laser powder-bed fusion, the near-eutectic Al–10Ce–1 Fe alloy exhibits greatly refined Al10CeFe2 and Al11Ce3 eutectic phases with a doubling in microhardness, indicating a strong potential for laser-based additive manufacturing. Cast Al–Ce–Fe-based alloys show great promise as low-cost alloys with high creep- and coarsening-resistance for use at high temperatures, with the high Fe tolerance enabling the use of recycled aluminum with high Fe contamination.

Beneficial Utilization of Electromagnetic Stirring Technology in Al-Ce Alloys

Beneficial Utilization of Electromagnetic Stirring Technology in Al-Ce Alloys

Strengthening of Mg–Al–Ca alloys with C15 and C36 Laves phases

Laves phases such as CaMg2 (C14), Ca(Al,Mg)2 (C36), and CaAl2 (C15) have high melting points, high hardness at room and elevated temperatures, but are inherently brittle. Cast Mg–Al–Ca alloys having Laves phase skeleton thus have good creep properties but limited ductility. An understanding of the co-deformation behaviour of α-Mg and Laves phases is essential for further improving the mechanical performance of these alloys. Here, we study the mechanical behaviour of a Mg–4.65Al–2.82Ca alloy using micropillar compression in the α-Mg matrix, at α-Mg/C36 and α-Mg/C15 interfaces and in the C15 phase in combination with scanning electron microscopy. We show that both, C15 and C36 phases, provide considerable strengthening to the α-Mg matrix. The amount of strengthening primarily depends on the volume fraction and geometry of Laves phases in composite micropillars and correlates well with the iso-strain and iso-stress bounds predicted for α-Mg/C36 and α-Mg/C15 composites.Graphical

Enabling rapid X-ray CT characterisation for additive manufacturing using CAD models and deep learning-based reconstruction

Metal additive manufacturing (AM) offers flexibility and cost-effectiveness for printing complex parts but is limited to few alloys. Qualifying new alloys requires process parameter optimisation to produce consistent, high-quality components. High-resolution X-ray computed tomography (XCT) has not been effective for this task due to artifacts, slow scan speed, and costs. We propose a deep learning-based approach for rapid XCT acquisition and reconstruction of metal AM parts, leveraging computer-aided design models and physics-based simulations of nonlinear interactions between X-ray radiation and metals. This significantly reduces beam hardening and common XCT artifacts. We demonstrate high-throughput characterisation of over a hundred AlCe alloy components, quantifying improvements in characterisation time and quality compared to high-resolution microscopy and pycnometry. Our approach facilitates investigating the impact of process parameters and their geometry dependence in metal AM.

Refining mechanism and elevated-temperature mechanical properties of Al-Ce alloys solidified under super gravity field

We reported that the enhanced elevated-temperature mechanical property of Al-Ce alloy could be obtained by solidification under super-gravity field. The refinement of eutectic Al11Ce3 is detected, which can be ascribe to the enhancement of mass transfer under super-gravity field, affecting the nucleation rate and inhibiting the growth of eutectic phase for this irregular Al-Ce eutectic system. Interestingly, the refined eutectic Al11Ce3 is thermally stable even up to 400 °C thermal exposure without obvious coarsening, contributing to the enhancement of elevated-temperature mechanical properties (∼125.0 ± 9.1 MPa at 300 °C), which is ∼74.8% higher than that solidified under normal gravity field (∼71.5 ± 0.6 MPa). The refinement of eutectic Al11Ce3 with higher number density also contribute to the stress dispersion, the crack prefer to propagate through the eutectic colony, leading to the transformation of fracture mode from brittle to ductile.

Solidification Kinetics of an Al-Ce Alloy with Additions of Ni and Mn

Heat-treated aluminum–silicon (Al-Si)-based alloys have dominated the cast lightweight alloy industry for several decades. However, in the last decade, Al-Ce-based alloys have shown promise in replacing Al-Si alloys as they remove the need for costly heat treatments. As the properties of Al-Ce alloys depend on the as-cast microstructure, it is important to characterize the solidification kinetics of these alloys. Therefore, this study focused on characterizing the solidification of an Al-Ce alloy with additions of Ni and Mn (nominal composition Al-12.37Ce-3.26Ni-0.94Mn-0.12Fe in weight percent). The alloy was cast in a wedge mold configuration, resulting in cooling rates between 0.18 and 14.27 °C/s. Scanning electron microscopy (SEM) coupled with the energy dispersive x-ray spectroscopy (EDS) and differential scanning calorimetry (DSC) techniques characterized the evolution rate of solid phases. The SEM/EDS data revealed that an Al10CeMn2 phase was present at higher cooling rates. At lower cooling rates, near the center of the casting, a primary Al23Ce4Ni6 phase was more present. It was observed that up to 2.6 atomic percent (at.%) of Mn was dissolved in this primary Al23Ce4Ni6 phase, thereby removing a large portion of the available Mn for forming the Al10CeMn2 phase. DSC analysis showed differences in the samples’ liquidus temperatures, which indicated compositional variations. Inductively coupled plasma–atomic emission spectroscopy (ICP-OES) and Scheil solidification simulations correlated the compositional differences with phase formation, which agreed with the SEM and DSC results. This experiment provides insight into novel Al-Ce-Ni-Mn alloys and where their potential lies in industrial applications.

Atomistic simulation of the dislocation interactions with the Al2Ca Laves phase in Mg–Al–Ca alloy

The mechanical properties of Mg–Al–Ca alloys are significantly affected by their Laves phases, including the Al2Ca phase. Laves phases are generally considered to be brittle and have a detrimental effect on the ductility of Mg. Recently, the Al2Ca phase was shown to undergo plastic deformation in a dilute Mg-Al-Ca alloy to increase the ductility and work hardening of the alloy. In the present study, we investigated the extent to which the deformation of Al2Ca is driven by dislocations in the Mg matrix by simulating the interactions between the basal edge dislocations and Al2Ca particles. In particular, the effects of the interparticle spacing, particle orientation, and particle size were considered. Shearing of small particles and dislocation cross-slips near large particles were observed. Both events contribute to strengthening, and accommodate to plasticity. The shear resistance of the dislocation to bypass the particles increased as the particle size increased. The critical resolved shear stress (CRSS) for activating dislocations and stacking faults was easier to reach for small Al2Ca particles owing to the higher local shear stress, which is consistent with the experimental observations. Overall, this work elucidates the driving force for Al2Ca particles in Mg–Al–Ca alloys to undergo plastic deformation.

A novel process to recycle coal gasification fine slag by preparing Si-Fe-Al-Ca alloy

Maximizing the use of valuable components in coal gasification slag is of great significance for resource recovery and the environment due to the huge annual emission of coal gasification slag. This study successfully produced Si–Fe–Al–Ca alloy with a composition of 63.83 wt% Si, 19.73 wt% Fe, 7.09 wt% Al, 6.32 wt% Ca, 1.70 wt% Ti, 0.03 wt% P, 0.66 wt% Mn, 0.05 wt% Cr, 0.53 wt% C, and 0.06 wt% others through electric arc furnace smelting from mixed coal gasification fine slag. The alloy composition is close to the standard 65% ferrosilicon, which can be used in the deoxidation of the molten steel industry. Moreover, the alloy yield was increased from 20.53% to 67.78% by using the residual carbon of the coal gasification slag as the reductant directly instead of adding petroleum coke. The transformation of coal gasification fine slag during the smelting process and the formation mechanism of the alloy were studied and the carbothermal reduction mechanism of Al2O3 and CaO can be explained by the reduction and decomposition theory of carbides. The complex liquid phase of the reactant system and product system in the smelting process made the carbothermal reaction of Al2O3 and CaO easier to occur, but it also brought the problem that the reactions were not fully completed.

Investigation on microstructure evolution and mechanical properties of Mg–Li–Al–Ca alloy after a series of heat treatments

Four heat treatment process routes were designed to study the microstructure evolution and mechanical properties of Mg–Li–Al–Ca alloy in relation to the heat treatment process. After heat treatment (Mg,Al)2Ca phase decomposed, and Li element volatilized. A large number of fine α-Mg precipitated phases appeared in β-Li matrix. The optimum mechanical properties of heat-treated alloy were obtained at 350 °C for 120 min, which are 190 MPa and 12% for tensile properties and 507 MPa and 51.9% for compression properties. Segregation of Al and Ca element was observed at grain boundaries. The phase boundaries between newly precipitated α-Mg phase and β-Li matrix impeded the slip of dislocations. It is believed that both the precipitation strengthening due to the formation of α-phase and the solid solution strengthening enhanced by the decomposition of (Mg,Al)2Ca phase play crucial roles in the improvement of mechanical properties.

Primary phase transformation mechanism in a hypereutectic Al-Ce alloy during rapid solidification

Cooling rate plays an important role in determining the microstructure in as-cast aluminum alloys. To obtain a cooling rate gradient, a wedge Cu mould was selected. Here, we found a transition from hypereutectic to hypoeutectic microstructures in a hypereutectic Al-Ce alloy during rapid solidification. There was a distinct interface at a cooling rate of 1598 K/s. When the cooling rate was lower than 1598 K/s, the microstructures were composed of primary Al11Ce3 phases and Al/Al11Ce3 eutectic colonies. As the cooling rate was higher than 1598 K/s, the primary Al11Ce3 phases transformed into α-Al. Compared with the α-Al, the nucleation of Al11Ce3 phases was more favorable because of the lower nucleation energy. The growth rate of α-Al was higher than that of Al11Ce3 phases as the undercooling was larger than 182 K. Primary phase transformation mechanism in the hypereutectic Al-Ce alloy was controlled by nucleation and growth of α-Al and Al11Ce3 phases.

Investigating the failure behavior of cast Al-11Ce-0.4Mg alloys using in-situ scanning electron microscopy tensile testing

Within the last decade, research on Al-Ce-Mg alloys has reported promising results for use in cast part applications. In this paper, the failure behavior of cast Al-11Ce-0.4Mg (wt%) was investigated experimentally with focus on the effect the matrix and intermetallic phases have on the fracture propagation behavior at failure. For the first time, in-situ SEM tensile testing was used to study the failure behavior of cast Al-Ce alloys, reporting results for uniaxial, DIC, and single edge notch tensile tests. The results of the in-situ SEM tensile testing were compared with the materials characterization experiments, which included serial sectioning, EBSD, EDS, and fractography. Analysis of EBSD and EDS mapping of cast Al-11Ce-0.4Mg showed that the cast microstructure was a hypereutectic two phase Al-Ce alloy with grains encompassing large complex colonies of laminar eutectic Al11Ce3 intermetallic. The uniaxial tensile results reported the effect casting defects have on the strength and ductility of the alloy, and DIC in-situ testing showed that the eutectic colonies plastically deform less than the matrix phase. In-situ SEM single edge notch tensile testing displayed how the strength of an individual phase affected the crack propagation direction in the alloy. The results of both the materials characterization and in-situ tensile testing experiments on the failure of this alloy revealed further directions for future alloy development that can improve both the strength and fracture toughness of Al-Ce-Mg alloys.