High-temperature Aluminum Alloys Research Articles

Experimental study of diffusion coefficients and assessment of atomic mobilities in FCC Al–Cu–V alloys

With the increasing demand for high-temperature aluminum (Al) alloys, there is a need for fundamental kinetic information to guide their design and development. This study investigates the diffusion behavior of the FCC Al–Cu–V system and assesses the atomic mobility parameters. Diffusion couples were assembled and annealed at 530, 555, and 580 °C for 1500 h to facilitate solute diffusion. The concentration profiles of Cu and V were measured using electron probe microanalysis (EPMA), and the diffusion coefficients were extracted using the Forward Simulation Analysis (FSA) method. The atomic mobility parameters for the Al–Cu–V system were assessed using the diffusion models in the DICTRA software program and verified by validation experiments involving annealing at temperatures of 535 and 565 °C for 1500 h. The activation energies for the diffusion of Cu and V were calculated and analyzed. The results reveal that adding Cu increased the diffusivity of V, while adding V decreased the diffusivity of Cu within the Al–Cu–V system. These findings of the kinetics of the FCC Al–Cu–V system would be beneficial for alloy design and processing optimization.

An additively manufactured heat-resistant Al-Ce-Sc-Zr alloy: Microstructure, mechanical properties and thermal stability

In this study, a high-strength and heat-resistant Al–Ce–Sc–Zr alloy was designed and fabricated by additive manufacturing. The as-built alloy shows an excellent combination of strength and ductility compared to other Al–Ce-based alloys, including an ultimate tensile strength of 445 MPa, a yield strength of 344 MPa and an elongation of 10%. Even at 300 °C, the alloy still retains a superb tensile yield strength of 233 MPa, which is the best among the high-temperature aluminum alloys reported so far. The excellent performance is mainly attributed to a significant amount of fine, homogeneous and coarsening-resistant Al11Ce3 intermetallic nanoparticles formed during the rapid solidification process of laser additive manufacturing. The formation of coherent Al3(Sc, Zr) nano-precipitates and interfacial segregation at the interface of intermetallic nanoparticles during high temperature exposure further improve the high temperature properties of the alloy. Our work has the potential to provide design concepts for the development of novel high temperature aluminum alloys.

A creep-resistant additively manufactured Al-Ce-Ni-Mn alloy

Existing additively manufactured aluminum alloys exhibit poor creep resistance due to coarsening of their strengthening phases and refined grain structures. In this paper, we report on a novel additively manufactured Al-10.5Ce-3.1Ni-1.2Mn wt.% alloy which displays excellent creep resistance relative to cast high-temperature aluminum alloys at 300–400 °C. The creep resistance of this alloy is attributed to a high volume fraction (∼35%) of submicron intermetallic strengthening phases which are coarsening-resistant for hundreds of hours at 350 °C. The results herein demonstrate that additive manufacturing provides opportunities for development of creep-resistant aluminum alloys that may be used in bulk form in the 250–400 °C temperature range. Pathways for further development of such alloys are identified.

High-strength and ductile ultrafine-grained Al–Y–Ni–Co alloy for high-temperature applications

Ultrafine-grained Al90.4Y4.4Ni4.3Co0.9 was synthesized by powder metallurgy from partially-amorphous powder precursors. A good combination of mechanical properties was obtained by optimizing size and density of second phases. The resultant alloy shows high specific strength and specific modulus as well as a tensile ductility of ∼5% at room temperature. Particularly, this alloy exhibits good mechanical stability at elevated temperature, which is superior to most high-temperature aluminum alloys. These results provide evidence for the effectiveness of Al-based metallic glasses as precursors for the development of high-temperature aluminum alloys.

Universality of the Principle of Sufficiency for Ultrasonic Technologies in Liquid Media

Using an ultrasonic technology as an example, we showed the validity and universality of the principle of sufficiency proposed by Dobatkin for various economics fields. A 25-mm-thick compacted material having no solid granules is fabricated when a stream of a molten grade 1973 alloy with high transition metal contents (0.63% Zr, 0.27% Cr, 0.88% Ni) is subjected to ultrasonic gas spraying at a pressure of 25 MPa and an acoustic treatment level of 164 dB. The layer-by-layer joining of solid–liquid granules takes place at 25–35% liquid phase. No primary transition metal intermetallics are observed in the structure of the compacted material. This structure is homogeneous, the average grain size is 5–10 μm, and the dendritic parameter does not exceed 10 μm. Therefore, a traditional granulation technology can be replaced by ultrasonic gas spraying to solve certain problems, such as the production of thin-walled sheets of high-strength or high-temperature aluminum alloys. A colloidal solution with a ζ potential of –15.4 mV and an average nanoparticle size of 200 nm is fabricated during the action of ultrasound on elemental selenium granules in distilled water by an and-face waveguide at a frequency of 22.4 kHz and a power of 300 W. As a result, we fabricated biologically active selenium-containing substances without chemically synthesized substances for medicine and agriculture purposes.

Optimization of the Composition and Structure of Deformable Heat Resistant Aluminum Alloy

The necessity of finding scientifically grounded methods for the development of new heat-resistant, wear-resistant and corrosion-resistant aluminum alloys is presented in the present work. For this purpose, the analysis of modern methods for computer calculation of phase diagrams in multicomponent metal systems using the Thermo-Calc program was carried out. Therefore, a quantitative analysis of the phase diagram the Al-Cu-Mn-Zr system was carried out, as the basis of deformable high-temperature aluminum alloys. Isothermal and polythermal sections of the phase diagram were calculated in this system. The temperatures of phase transformations were calculated. The mass and volume fractions of the phases in the studied alloys were calculated. The range of concentrations and temperatures at which the maximum amount of dispersoids Al20Cu2Mn3may be achieved, was defined. The minimum amount of Al2Cu phase is calculated, which should correspond to the best heat resistance of alloys. It is substantiated that in the alloys of a new generation of ALTEK type, the use of homogenization and quenching operations is inexpedient, which implies the possibility of a significant reduction in the cost of heat treatment in comparison with industrial alloys, such as 1201.

Improved High-Temperature Aluminum Alloys Containing Cerium

A common rare earth (cerium) when added to aluminum in compositions up to the eutectic compositions of around 10 wt.% improves the high-temperature performance of aluminum alloys. In the early 1980s, some promising research and development efforts focused on powder metallurgy revealed that aluminum alloys containing 4 wt.% cerium exhibit high-temperature mechanical properties exceeding those of the best commercial aluminum casting alloys then in production. Those compositions, which also included high levels of iron, were difficult to process. Recently, magnesium replaces iron to reduce density and improve processing. Cerium oxide is an abundant rare earth oxide that is often discarded during the refining of more valuable rare earths such as Nd and Dy. Therefore, the economics are compelling for cerium as an alloy additive. In this review, we report results obtained during an investigation of the processing and properties of aluminum-cerium alloys produced via casting, extrusion and additive manufacturing. The results show mechanical properties are retained at higher temperatures than other aluminum alloys and show complete recovery of mechanical properties at room temperature when exposed to elevated temperatures as high as 500 °C for 1000 h. Alloys containing cerium also have superior corrosion properties when compared to most aluminum alloys.

Rapidly Solidified High-Temperature Aluminum Alloys. II. Mechanical Properties

The strength and plasticity of a series of rapidly solidified high-temperature aluminum alloys determined in tensile tests are analyzed over a wide temperature range. The properties of the following systems are studied: Al–Fe–Ce, Al–Fe–Cr–(TM), Al–Cr–Zr(Mn), and Al–Fe–V(Mo)–Si. The effect of the doping content and rapid solidification technique on strength is examined. The best samples of green products show 550–600 MPa strength at room temperature and at least 200–250 MPa at 300°C. The strength of Al–Fe–Cr–(TM) alloys with a high volume content of quasicrystals is approximately 100 MPa higher at 20 and 300°C, while their elongation is 50 to 67% lower than the corresponding characteristics of other materials.

Rapidly solidified high-temperature aluminum alloys. I. Structure

The paper examines the phase composition of a number of high-temperature aluminum alloys formed in rapid solidification. The main strengthening phases and associated phase transitions in Al–Fe–Ce, Al–Fe–Cr–(TM), Al–Cr–Zr(Mn), and Al–Fe–V(Mo)–Si alloys have been studied. The phase composition of the alloys is shown to be critically dependent on the cooling rate. High-temperature materials are particularly sensitive to the solidification rate since they are doped by nonsoluble elements. Fine quasicrystalline phases, which make a significant contribution to strengthening at low and high temperatures, are present in rapidly solidified materials doped with iron. Besides these phases, Al3TM intermetallics characterized by high thermal stability and low coarsening rate play an important role in modern materials.

Coarsening resistance at 400 °C of precipitation-strengthened Al–Zr–Sc–Er alloys

The effect of substituting 0.01 or 0.02 at.% Er for Sc in an Al–0.06 Zr–0.06 Sc at.% alloy was studied to develop cost-effective high-temperature aluminum alloys for aerospace and automotive applications. Spheroidal, coherent, L1 2-ordered Al 3(Sc, Zr, Er) precipitates with a structure consisting of an Er-enriched core surrounded by a Sc-enriched inner shell and a Zr-enriched outer shell (core/double-shell structure) were formed after aging at 400 °C. This core/double-shell structure strengthens the alloy, and renders it coarsening resistant for at least 64 days at 400 °C. This structure is formed due to sequential precipitation of solute elements according to their diffusivities, D, where D Er > D Sc > D Zr at 400 °C. Zr and Er are effective replacements for Sc, accounting for 33 ± 1% of the total precipitate solute content in an Al–0.06 Zr–0.04 Sc–0.02 Er at.% alloy aged at 400 °C for 64 days. Er accelerates precipitation kinetics at 400 °C, resulting in: (i) strengthening due to the elimination of lobed-cuboidal precipitates in favor of spheroidal precipitates; and (ii) a decrease in the incubation time for nucleation because D Er > D Sc. Finally, a two-stage aging treatment (24 h at 300 °C + 8 h at 400 °C) provides peak microhardness due to optimization of the nanostructure.

Ways of developing high-strength and high-temperature structural aluminum alloys in the 21st century

An analysis of the development of aluminum alloys in the 20th century is made on the basis of the author’s works in almost 40 years. It is inferred that advances in high-strength and high-temperature aluminum alloys will occur in the 21st century primarily by introducing transition and rare-earth metals into their composition.

Some studies on Al–8.3Fe–0.8V–0.9Si alloy for near net shape casting

With the development of new generation high temperature aluminium alloys, simple techniques to produce them to near net shape by casting route have become necessary. It is well known that near net shape casting not only contributes to material saving but also to reduction of processing steps. Amongst the high temperature aluminium alloys, the Al–Fe–V–Si alloys system has attracted considerable interest due to its potential in automotive and aerospace applications. These alloys are generally prepared through the complex rapid solidification–powder metallurgical processing route. Thus, although the alloys possess good elevated temperature strength, ductility, fatigue and fracture toughness they have not found industrial application. An alternative method of conventional solidification for producing these alloys has been attempted in this work. A novel structural modification technique has been tried out with Mg/Ni–Mg master alloy to bring about alteration and refinement of the precipitate particles, which are otherwise ten-armed star-shaped and adversely affect the mechanical properties, to favourable cuboidal, hexagonal or other compact forms. It was observed that a number of arrest points occur in the cooling curve of the alloy, indicating that a variety of phases such as Al 12(Fe,V,Si) 6(Si,Mg) 5, Al 15(Ni,V,Fe) 6(Si,Mg), Al 3(Fe,V,Ni,Si,Mg) form during cooling. Quenching experiments were performed to identify the details of the phases formed. The features of the phases were studied using scanning electron microscope/EDAX and X-ray diffraction. Important properties required for near net shape casting such as the thermal expansion coefficient, fluidity, etc., have been studied and correlated with the phases.

A Study of the Properties of Semiproducts from High-Temperature Aluminum Alloys in the State of Maximum Permissible Softening

A Study of the Properties of Semiproducts from High-Temperature Aluminum Alloys in the State of Maximum Permissible Softening

Comparative analysis of crack-resistance characteristics of semiproducts from high-strength aluminum alloys

Comparison of the characteristics of static strength and crack resistance of pressed and rolled semiproducts from series-produced high-temperature aluminum alloys in state T1 shows that sheets of alloys AK4-2ch, VD17, and 1215 have the best combination of properties.

Extrusion processing parameter–mechanical property correlations in rapidly solidified Al–6·7Fe–5·9Ce and Al–6·2Fe–5·9Ce–1·63Si (wt-%) alloy powders

High temperature aluminium alloys containing iron and cerium additions have promising mechanical properties, particularly with regard to thermal stability. Development of these alloys has been possible because of advances in rapid solidification technology. The advantage of rapid solidification is that it produces extended solid solubility or a high volume fraction of strengthening dispersoids depending on the cooling rate. To retain the microstructural advantages of rapid solidification, it has generally been thought necessary to process these alloys at the lowest possible temperature. The present work indicates that for optimum strength levels this is correct but that the greater homogeneity of microstructure produced by higher processing temperature leads to improved ductility and toughness. The present investigation was undertaken to find suitable extrusion processing conditions for two rapidly solidified high temperature aluminium alloys having the compositions Al–6·7Fe–5·9Ce and Al–6·2Fe–5·9Ce–1·63Si (all wt-%). Silicon was added to Al–Fe–Ce in an attempt to form the Al12(Fe,Ce)3Si phase, which if formed might improve the thermal stability of the alloy (similar to the Al12(Fe,V)3Si phase in the Al–Fe–V–Si system). Both the alloys were extruded in the temperature range 400–500°C at a constant extrusion ratio of approximately 10:1 and ram speed of 3 mm s−1. The room temperature mechanical properties of all the extrudates were measured for both alloys and the values obtained were compared with those for other high temperature aluminium alloys such as Al–5Cr–2·2Zr and Al–8·3Fe–4·8Zr. High temperature tensile properties were measured for extrudates processed at 400 and 450°C. The results obtained for the low temperature (400°C) extrudate were found to be satisfactory when compared with US Air Force Materials Laboratory (AFML) goals for high temperature aluminium alloys. Attempts have been made to explain the properties on the basis of the microstructures of the extrudates, which were characterised using transmission and scanning electron microscopy and X-ray diffraction.MST/1615

High temperature aluminium alloys for aerospace applications : P.S. Gilman, (Allied-Signal Intl, Morristown, New Jersey, USA)

High temperature aluminium alloys for aerospace applications : P.S. Gilman, (Allied-Signal Intl, Morristown, New Jersey, USA)

Fabrication of rapidly solidified high temperature aluminium alloys

Fabrication of rapidly solidified high temperature aluminium alloys

High-temperature materials — a general review

Materials that allow operation at high temperature are essential in many industries from material producing and processing to transportation and power generation. After brief comments on typical operating environments, high-temperature aluminium alloys, steels and nickel alloys are discussed, referring to alloy types, characteristics and applications. Future development possibilities are indicated. The engineering ceramics silicon nitride and silicon carbide are discussed with particular emphasis on defect tolerance considerations. The various forms and applications of high-temperature carbon, including carbon-carbon composite, are included and a discussion on “engineered materials” concepts, such as thermal insulators and ablative materials, concludes the review.

Applications of Rapidly Solidified High Temperature Aluminum Alloys

Applications of Rapidly Solidified High Temperature Aluminum Alloys

High performance aerospace alloys via rapid solidification processing

Recent progress in the rapid solidification processing of metallic materials has opened new horizons for alloy design, expanding the ranges of possible microstructures and alloy compositions beyond those readily achieved through conventional technology. Alloy systems incorporating high volume fractions of ultrafine dispersed phases can now be produced, yielding corrosion and oxidation resistances and combinations of toughness and elevated temperature strength hitherto considered impossible. The particular examples discussed here are those of high strength corrosion-resistant magnesium alloys, AlLi alloys of reduced density, high temperature aluminum alloys and titanium alloys. In reviewing the design of these alloys, we shall discuss the interplay between the selection of alloy chemistry, the solidification kinetics characteristic of various rapid solidification powder production processes and the thermomechanical processing of the rapidly solidified powders. These three areas form links in a continuous chain, none of which can be neglected if the final product is to have the desired properties.