Cast Alloy Research Articles

Recycling of aluminium scrap into phase change materials for high-temperature storage applications: Thermophysical properties and microstructural characterisation

Metal scrap is often generated during conventional production processes and at the end-of-life of metallic components finding use as a recycled metal source. However, the impurities introduced in the recycling process can deteriorate the mechanical properties of the final product leading to down-cycling from structural applications or requiring great effort to make the material viable again.Metallic phase change materials (mPCMs) are promising materials due to their high energy storage density and high thermal conductivity relative to common inorganic and organic thermal storage materials. Metals used for thermal applications, such as mPCMs do not have strict mechanical requirements, and could potentially be made from recycled sources unsuitable for structural significant applications. Thermal storage offers an alternative use for scrap sources, especially aluminium alloys which according to the International Energy Agency are among the metals with the highest recovery rates.AlSi cast alloys are widely used in different applications, especially the automotive industry. In this work, the eutectic composition Al-12.6 wt% Si has been proposed as thermal storage material due to the great potential and excellent storage properties in the temperature range 500–600 °C. Thermophysical properties including melting temperature, heat of fusion, heat capacity and thermal diffusivity were experimentally determined via Differential Scanning Calorimetry (DSC) and Light Flash Analysis (LFA) in order quantify the impact of impurities typically present in commercial aluminium alloys such the 2000 and 3000 series.Four different AlSi alloys with different impurity levels from scrap-equivalent compositions were investigated as candidate materials for latent heat storage applications and their potential contribution in the circular economy.

Impact of Processing Conditions on the Fluidity and Consistency of GISS-Processed Semi-Solid Aluminum Alloys

GISS (Gas Induced Superheated Slurry) is one of the more popular processes for the production of commercial semi-solid castings. For the successful production of high-quality castings, it is necessary to understand the impact of processing parameters on the flow behavior of the semi-solid metal. This paper describes the results of laboratory studies to examine the effects of processing conditions on the development of semi-solid feed material during GISS processing for two aluminum casting alloys, ADC12 and A356. Two series of tests were performed. The first involved a simple pouring test along an inclined section of a v-channel, to determine if differences in flow behavior could be identified. The second series of trials examined the effect of processing temperature and time on the consistency and flow behavior of the aluminum alloys. Ladles of molten aluminum alloy were treated using the GISS process at different temperatures for between zero and 10 seconds. After the treatment, the alloy was allowed to further cool in the ladle into the semi-solid temperature range, at which time the flow behavior of was compared. Consistency more suited to semi-solid casting was obtained when the GISS treatment temperature was lower and treatment time longer.

Study on Processing Conditions for Semi-Solid Forging of Magnesium Alloys

Magnesium alloy castings are mainly formed by the die casting method, but this method has the disadvantage that product properties such as strength vary due to many defects inherent in casting. In this study, AZX912 (a flame-retardant magnesium alloy with 2% calcium added to AZ91D alloy) was semi-solid forged using a servo press and die cushion system to stabilize product properties. Experiments were conducted to refine the α-phase and reduce the yield point, and the stirring speed was changed and its effect was investigated. Observation of the microstructure of the molded product using an optical microscope showed that the average grain size of the α-phase became smaller as the stirring speed increased. Tensile tests were conducted on specimens cut from the compacts, and the yield point increased as the stirring speed increased. This is thought to be due to compliance with Hall Petch's law. The microstructure of the molded product was observed under an optical microscope and showed a three-layer structure with a dendrite shape in the upper part (about 5%), a grain structure in the middle part (over 90%), and a chill layer in the lower part (less than 5%). Comparison of the thickness of the chill layer showed that the thickness of the chill layer decreased as the solidus ratio increased.

Microstructure features induced by fatigue crack initiation up to very-high-cycle regime for an additively manufactured aluminium alloy

Fatigue failure can still occur beyond 107 cycles, i.e. very-high-cycle fatigue (VHCF), in many metallic materials, such as aluminium alloys and high-strength steels. For VHCF of high-strength steels, a fine granular area (FGA) surrounding an inclusion is commonly identified as the characteristic region of crack initiation on the fracture surface. However, no such FGA feature and related crack initiation behaviour were observed in VHCF of conventionally cast or wrought aluminium alloys. Here, we first reported the distinct mechanisms of crack initiation and early growth, namely the microstructure feature and the role of FGA in VHCF performance for an additively manufactured (AM) AlSi10Mg alloy. The AM pores play a key role in fatigue crack initiation similar to that of the inclusions in high-strength steels, resulting in almost identical FGA behaviour for different materials under a range of mean stress with a stress ratio at R < 0 or R > 0. The profile microstructure of FGA is identified as a nanograin layer with Si rearrangement and grain boundary transition. This process consumes a large amount of cyclic plastic energy making FGA undertake a vast majority of VHCF life. These results will deepen the understanding of VHCF nature and shed light on crack initiation mechanism of other aluminium and AM alloys.

Effect of Cu Addition on Properties of an Al-La Alloy

The effect of copper content on the microstructure and properties of an aluminum copper alloy containing lanthanum was studied by adding 0.5 wt% lanthanum and different contents of copper to the 2A12 alloy. We used a universal testing machine, Brinell hardness tester, and friction and wear testing machine to test the mechanical properties of the alloy. The microstructure and phase composition of the alloy were analyzed using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The results show that, after adding La and Cu, the alloy grain is refined, and the fracture mode changes from dissociation fracture to quasi dissociation fracture. A new phase containing La accumulates at the grain boundary. If the amount of Cu added is too large, the tendency for hot cracking increases, which can easily lead to the formation of voids or even cracks. The tensile strength and hardness of the cast alloy significantly increase with the increase in Cu addition. In the range of adding 2 wt% to 5 wt% Cu, the tensile strength and hardness of the cast alloy increases by approximately 12% and 17.84%, respectively, compared with the original alloy. With the increase in Cu addition, the elongation of the alloy first increases and then decreases, reaching its maximum value when Cu addition is 3 wt%. Adding Cu is beneficial for improving the wear resistance of the alloy. When the addition of Cu is 3 wt%, the alloy has the best wear resistance and minimum wear amount. This is due to the enrichment of La and Cu at the grain boundaries, forming new La phases or other phases with higher hardness, which changes the properties of the alloy. It shows that the content of Cu in the 2A12 alloy can be increased to 7-8% with the increasing of additional rare-earth elements, and a new Al-Cu (7 wt% to 8 wt%)-Mg (1.2 wt% to 1.8 wt%)-Mn (0.3 wt% to 0.9 wt%)-La (0.5 wt%) alloy, in which tensile strength, hardness, and elongation of the alloy are increased by 8.1%, 16%, and 79.1%, respectively, can be formed. In addition, the wear resistance of Al-La alloys also improves significantly with the addition of copper content. The coefficient of friction is reduced by 68% compared with no copper addition.

Evolution of Microstructure and Mechanical Properties of the Rheo-Diecast Mg-12Gd-3Y-1Zn-0.4Zr Alloy during Heat Treatment

The SEED (Swirled Enthalpy Equilibrium Device) process is the typical high solid fraction (with about 40-60% of solid) rheo-diecast process. The high strength Mg-12Gd-3Y-1Zn-0.4Zr magnesium alloy was successfully produced using SEED process. The microstructure and mechanical properties of rheo-diecast Mg-12Gd-3Y-1Zn-0.4Zr alloy during solution and ageing heat treatment process were studied in this paper. Optical microscopy (OM) and transmission electron microscopy (TEM) were employed to study the evolution of microstructure and mechanical properties. The cast alloy exhibited a microstructure consisting of equiaxed primary solidified grains and together with eutectics. The eutectics were partially dissolved into a-Mg matrix after solution heat treatment. The tensile properties of rheo-diecast Mg-12Gd-3Y-1Zn-0.4Zr alloy were substantially enhanced after T6 heat treatment.

On the Possibility of Replacing Scheil-Gulliver Modeling with Machine Learning and Neural Network Models

Resource-efficient manufacturing is a foundation for sustainable and circular manufacturing. Semi-solid processing typically reduces material loss and improves productivity but generally requires a better understanding and control of the solidification of the cast material. Thermal analysis is commonly used in high-pressure die casting (HPDC) processes to determine casting process parameters, such as liquidus and solidus temperatures. However, this method is inadequate for semi-solid casting processes because the eutectic temperature is also a crucial parameter for successful semi-solid casting. This study explores the feasibility of using machine learning and artificial neural networks to predict fundamental values in Al-Si alloy casting. The Thermo-Calc 2022 software Scheil-Gulliver calculation function was used to generate the training and the test datasets, which included features such as melting temperature, alpha aluminium solidification temperature, eutectic temperature, and the solid fraction amounts at eutectic temperature. The results show that both models have a symmetric mean absolute percentage error (SMAPE) of less than 2 % with temperature prediction, with the machine learning model achieving a better accuracy of less than 1 %. A case study comparing practical measurements with prediction results is also discussed, demonstrating the potential of AI methods for predicting semi-solid casting processes.

Strengthening mechanisms and work hardening in a heterostructured cast aluminum alloy under compressive loading: Correlation with nanomechanical properties

The compressive deformation behavior of a high-pressure die-cast Silafont®-36 aluminum alloy was evaluated in relation to the microstructural changes during deformation. No strain rate sensitivity was observed for the alloy compressed at room temperature. The as-cast microstructure consisted of softer primary α-Al dendrites and harder Al-Si eutectic structure, which was well depicted by the difference in the nanohardness values using high-speed nanoindentation mapping. The load-bearing capacity of eutectic Si particles and thermal mismatch enhanced dislocation density strengthening were identified to be the predominant strengthening mechanisms in the alloy, plus a certain degree of Orowan strengthening mechanism. The work hardening capacity of the cast alloy was mainly attributed to the increase in the dislocation density in the softer α-Al matrix, which was further assisted by the presence of eutectic Si particles. The relative increase in the flow stresses also corresponded well to that in the nanohardness values of the α-Al grains with increasing strain levels.

Effect of Mg on elevated-temperature low cycle fatigue and thermo-mechanical fatigue behaviors of Al-Cu cast alloys

The effects of Mg addition on the cyclic deformation and fatigue life behaviors of Al-Cu 224 cast alloys were investigated under isothermal low cycle fatigue (LCF) at 300 °C and out-of-phase thermo-mechanical fatigue (OP-TMF) in the temperature range 60–300 °C. The results show that all tested alloys experienced cyclic softening during both LCF and OP-TMF, whereas the softening ratio of Mg-containing alloys was lower than that of the base alloy free of Mg because of the lower coarsening rate of θ'-Al2Cu precipitates. Under both LCF and TMF, near-surface porosity and brittle intermetallic particles were considered sources of crack initiation. TMF lives were inferior to LCF lives under the same strain amplitude because of the combined damage effect of the cyclic mechanical and thermal loadings. Under LCF, the addition of Mg enhanced the fatigue performance because of the co-existing θʹ and θʺ precipitates and the higher thermal resistance of θʹ; under TMF, it led to a slight reduction in fatigue performance. The hysteresis energy model was successfully applied to predict the LCF and TMF lifetimes. The predicted results agree well with the experimentally measured LCF and TMF lifetimes.

Consumable additive FDM models in the production of aluminum alloy castings

This article describes the results of a study aimed at improving production technology of experimental castings from aluminum alloys by investment casting using models produced by 3D printing. The consumable models were produced using fused deposition modeling (FDM). Biodegradable polylactide (PLA) was used as a material for the models. In order to decrease the surface roughness of consumable PLA model. chemical post-treatment by dichloromethane needs to be performed. After immersion of the model into the solvent for 10s, its surface becomes smooth and glossy. Three-point static bending tests of PLA plates demonstrated a mechanical strength of average ~45.1 MPa. A thermomechanical analysis of polylactide demonstrated that in the course of heating of ceramic shell in excess of 150 °C, the polylactide model begins to expand intensively by exerting significant pressure on the ceramic shell. In order to decrease stress during the removal of polylactide model from ceramic mold, the heating time in the range of 150–300 °C needs to be heated to a maximum. The use of hollow consumable casting models with a cellular structure not higher than 30 % is also sensible. The stresses on the shell will not exceed its strength. Characteristic temperature properties of PLA plastic thermal destruction were detected using thermogravimetric analysis. Polylactide was established to completely burn out upon heating to 500 °C leaving no ash residue. Analysis of the results identified the burning modes of polylactide models from ceramic molds. Using a Picaso 3D Designer printer (Russia), the PLA models were printed used for production of experimental castings from aluminum alloys. It was revealed that the surface roughness (Ra) of a casting produced using a consumable model treated by dichloromethane decreases by 81.75 %: from 13.7 to 2.5 μm.

Effect of Structural Features on Microstructure and Properties Homogeneity Based on Quantification and Statistical Analysis for Large-Scaled Complex Titanium Alloy Castings

Effect of Structural Features on Microstructure and Properties Homogeneity Based on Quantification and Statistical Analysis for Large-Scaled Complex Titanium Alloy Castings

Analysis of Casting Defects, Tensile Strength, and Hardness of AlSi Alloy Castings from Sand Casting Method with Bangkalan Local Clay Binder Variations

Analysis of Casting Defects, Tensile Strength, and Hardness of AlSi Alloy Castings from Sand Casting Method with Bangkalan Local Clay Binder Variations

Microstructure and Properties of FeCrMnxAlCu High-Entropy Alloys and Coatings

FeCrMnxAlCu (x = 0.5, 1, 1.5, and 2) high-entropy alloys (HEA) and coatings were prepared through vacuum arc melting and cold spray-assisted induction remelting processes. This study investigated the effect of different Mn contents on the microstructure and wear resistance of HEAs and coatings. The results showed that the high-entropy FeCrMnxAlCu alloy prepared through vacuum arc melting and cold spray-assisted induction remelting processes comprised simple body-centered cubic and face-centered cubic phases with dendritic + interdendrite structures. The coating of the prepared alloys exhibited superior performance compared with the cast alloy. In addition, the hardness of the FeCrMnxAlCu HEA coatings synthesized through induction remelting was 1.4 times higher than that of the cast FeCrMnxAlCu HEA. Moreover, the wear rate of induction-remelted produced HEA coating was reduced by 24% compared with that of vacuum arc-melted produced HEA. The hardness of the induction-remelted produced FeCrMnxAlCu HEA coating initially increased and then decreased with increasing Mn contents. At x = 1, the hardness of FeCrMnAlCu HEA coating reached a maximum value of 586 HV, with a wear rate of 2.95 × 10−5 mm3/(N·m). The main wear mechanisms observed in the FeCrMnxAlCu HEA coatings were adhesive, abrasive, and oxidative.

A comparative study of deformation behaviors and ductility improvement in Mg–Gd–Zr and Mg–Zr cast alloys

This study investigates the impact of Gd elements on the enhancement of ductility in the Mg–Gd–Zr alloy. The deformation behavior at room temperature of the cast Mg–Gd–Zr alloy and the cast Mg–Zr alloy was examined using the EBSD-assisted slip trace method. The quantitative analysis of the initiation ratio of each slip system in the two alloys revealed that the Mg–Gd–Zr alloy had a higher ratio of non-basal slip systems. The experimental determination of the critical resolved shear stress (CRSS) ratios of non-basal slip to basal slip for both alloys indicated that the Gd elements could reduce this ratio, facilitating the initiation of more non-basal slip systems to accommodate strain. Furthermore, the segregation of Gd elements at grain boundaries was observed to enhance the grain boundary strength of the alloy, which is a significant factor in the enhancement of ductility.

Development of Inoculants for Aluminum Alloy: A Review.

Aluminum and its alloys are widely used in packaging, transportation, electrical materials, and many other fields because of their abundance, light weight, good mechanical properties, suitable corrosion resistance, excellent electrical conductivity, and other advantages. Grain refinement achieved by adding inoculant is important not only to reduce the segregation and thermal cracking of alloy castings but also to improve the mechanical properties of alloy castings. Therefore, fine equiaxed grain structure has always been one of the goals pursued by the aluminum alloy casting industry. For this reason, the selection and development of effective inoculants for aluminum alloy is a key technology in the aluminum processing industry. This paper summarizes the development history of inoculants for aluminum alloy, including Al-Ti-C, Al-Ti-B, Al-Ti, Al-Ti-B-(C)-Ce, Al-Sc, and the Fe-rich phase of Al-Si alloy. At the same time, the advantages and disadvantages of common inoculants are introduced and prospective future applications are reviewed.

Effect of the Cooling Capability Difference Between Additively Manufactured Sand Molds on Shrinkage Defect in A356 Alloy Castings

Effect of the Cooling Capability Difference Between Additively Manufactured Sand Molds on Shrinkage Defect in A356 Alloy Castings

Effect of thermophysical properties on porosity and microstructure of laser welded cast and wrought aluminum alloy dissimilar lap joints

The influence of thermophysical properties of materials on the porosity and microstructure of dissimilar lap joints between laser-welded Al–Si–Mg cast and Al–Mg–Si–Cu wrought aluminum alloys was investigated. The low thermal conductivity and viscosity of the weld would promote bubble escape, while the high electrical conductivity of the base material would increase the melt depth and reduce the convection intensity in the melt pool, thus increasing the difficulty of bubble escape. The variation in thermophysical properties did not significantly impact the distribution of elements, the type of precipitated phases, and the dislocation density, however, it did affect grain morphology. Differences in thermal diffusion coefficients between base materials created conditions for constitutional supercooling, increasing the likelihood of a columnar-to-equiaxed transition. Moreover, the temperature difference between the liquid phase lines of the weld and base materials facilitated the liquid base material flushed into the weld to solidify before mixing, resulting in an “island” formation. This “island” acted as a heterogeneous nucleation site, leading to equiaxed grain layer formation in the lowest zone of the weld. The variations in thermophysical properties exerted an influence on the tensile strength by impacting both the melt depth and the grain morphology of the weld but did not yield a significant impact on the average microhardness.

Synchronous improvement in mechanical properties and corrosion resistance of Mg-Gd-Ag-Zr alloy through nanoprecipitates

It is still challenging to synchronously improve mechanical properties and corrosion resistance through one strategy during developing Mg alloys. Introducing high-density precipitates is an effective and popular approach to strengthen Mg alloys, while these precipitates generally degrade the corrosion resistance. In this paper, the nanoprecipitates are developed in Mg-13.4Gd-2.2Ag-0.4Zr wt.% cast alloy through the solution and aging treatment for evading this dilemma. Compared with its as-cast counterpart, the peak-aged alloy with high-density nanoprecipitates exhibits enhanced strength, comparable ductility, and improved corrosion resistance. The nanoprecipitates in the peak-aged alloy are composed of β nanoparticles at grain boundaries, and intragranular γ′′ and β′ nanoplates. These nanoprecipitates are contributed to the improved strength through the Orowan mechanism. The β nanoparticles induce weak galvanic corrosion, and the γ′′ nanoplates have not induced visible galvanic corrosion, thus contributing to the enhanced corrosion resistance of the peak-aged alloy. This result suggests that developing nanoprecipitate is a feasible route to collaboratively optimize the mechanical and corrosion properties of the Mg alloys.

RAFFMETAL EN AB-Al Si10Mg(Fe) (EN AB-43300)

Abstract Raffmetal EN AB-Al Si10Mg(Fe) (EN AB-43400) is an aluminum-silicon-magnesium casting alloy in ingot form for remelting. It is used extensively for producing high pressure die castings and low pressure die castings for applications requiring a combination of excellent casting characteristics, good strength with fair ductility, and good corrosion resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on casting and heat treating. Filing Code: Al-501. Producer or source: Raffmetal S.p.A.

Intermediate phase analysis of cast Al7075 after the addition of high-temperature oxides

Al7075 is a popular high-strength wrought alloy with higher potential in aerospace sectors. The present research focused on the intermediate phase formation during the casting of Al7075 alloy with the addition of high-temperature oxide additives. The intermediate phases in Al-Zn-Mg-Cu quaternary alloy formed at the grain boundaries or within the grains, and their formation at a specific location can be altered by mechanical, thermo-mechanical, or chemical treatment. A novel approach, adding high-temperature oxides - a chemical treatment, distributes the alloying elements by changing the segregation patterns and forming new phases. It results in microstructural changes that control mechanical properties. The 2.5 weight % of high-temperature oxides, ZrO2, TiO2, and ZrTiO4, were added into the melt of Al7075 alloy by die-casting. The addition of these oxides formed intermediate phases such as ƞ(MgZn2), S(Al2MgCu), and T(Mg3Zn3Al2) depending on the Zn/Mg ratio. XRD analysis finds the formation of different intermediate phases. The SEM-EDS analysis at different locations confirmed their presence. The elemental ratios of Zn/Mg decide the formation of intermediate phases and, based on their proportion, different phases were confirmed. Among ZrO2, TiO2, and ZrTiO4 addition, the ZrO2 addition alters the mechanical properties of Al7075.