Al Solid Solution Research Articles

Corrosion Assessment of Fe-Ni-Al Based Alloy in Saline Solution

The corrosion assessment of a Fe-Al-Ni alloy in saline solution was carried out by using electrochemical techniques. The Fe-Al-Ni alloy was produced by casting in an induction furnace. It was microstructural and chemically characterized by SEM, EDS XRD. The microstructural characterization results of the casting Fe-Ni-Al alloy showed a homogeneous microstructure morphology, with some porosities formed during the solidification process. The Fe-Ni-Al base alloy presented a B2-(Fe,Ni)Al solid solution phase and non-third phase was observed. The potentiodynamic results showed a more positive Ecorr value in the solution at pH 5. At the pH 7, the linear polarization resistance results showed the highest values of the icorr kinetic. Whereas, the best performance against corrosion was observed at pH 5, where the lowest icorr kinetic values were observed. This was associated to the formation of a more stable and dense scale of corrosion products at that condition.

Effect of chemical composition and T6 heat treatment on the mechanical properties and fracture behaviour of Al-Si alloys for IC engine components

The microstructural examinations of Al-Si alloys intended to manufacture IC engine components revealed a complex phase composition in all the samples. The polyhedral crystals of primary silicon were detected in the Al-12.5Si alloy, besides the ?-Al phase, eutectic silicon, and several intermetallic phases, identified in the cast samples of both alloys. Better tensile properties were found for the samples of Al-11Si. A predominantly intercrystalline fracture with features of ductile failure was observed in both alloys. In as-cast specimens of the Al-11Si alloy, the cracks were formed by the decohesion mechanism between the particles of the intermetallic phase AlCuFeNi and the ?-Al phase. The microcracks initiated on the interface were spread along the branches of the ?-Al15(Fe,Mn,Cu)3Si2 particles. After T6 treatment of the Al-11Si alloy, almost half of the intermetallics quantity presented the Al3Ni phase, while the iron-based phases were observed in a small amount. Spheroidized eutectic silicon, a smaller portion of Al5Cu2Mg8Si6, and a more considerable quantity of Al3(Fe,Mn,Cu,Ni,Co) were detected for T6 specimens of the Al-12.5Si alloy. The rounded crystals of eutectic silicon contributed to the improvement of their tensile properties. Larger and deeper dimples of mostly polygonal shapes were observed in the samples of the Al-11Si alloy after T6 treatment. The microcracks occurred at the boundary of the intermetallic phase/?-Al solid solution.

Synthesis and catalytical properties of hierarchical nanoporous copper from θ and η phases in CuAl alloys

Greenhouse gases, such as carbon dioxide, have a great impact on global warming and climate change. CO2 trapping and reduction have been one of the solutions to slow down the temperature rise. Copper has proven to be an effective electrocatalyst to transform CO2 into useful organic compounds, such as CH4, C2H4, and HCOOH. Here, nanoporous copper (NPC), that are synthesized from various precursor phases of Cu–Al alloys, like pure Al solid solution α, CuAl2 θ and CuAl η phases, with different relative densities and ligament sizes are being used as electrocatalyst for CO2 reduction reaction (CO2RR). The ligament sizes of the NPCs can be adjusted with the use of dealloying solution, either in HCl or NaOH, and dealloying temperatures. In this study, the ligament sizes were available from the range of 51–116 nm. A hierarchical structure containing a lamellar eutectic structure with an interlayer spacing of 6 μm in the parent phases is observed from NPC synthesized from Cu18Al82. The results show that the current density of CO2RR using NPC as electrocatalyst is 2–5 times higher than that of using copper foil. The ligament size effect is more obvious than the relative density effect since the peak current density was obtained from the NPC with ligament size of 76 nm. The product distribution suggested that NPC with hierarchical structure has higher Faraday efficiency of ethylene than conventional NPC or Cu foil at high overpotential.

Effect of V and Cr transition layers on microstructure and mechanical properties of Ni-based coating on titanium alloy fabricated by laser cladding

In current study, the Inconel 718 coating was prepared on the surface of Ti-6Al-4V by laser cladding. The transition composition route of Ti-6Al-4V alloy → V → Cr → Inconel 718 was designed to relieve tremendous differences of Ti and Ni in thermal physics properties and refrain undesirable intermetallic compounds at the interface between Inconel 718 coating and Ti-6Al-4V substrate. The microstructure and composition of different layers were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron back-scatter diffraction (EBSD). The mechanical properties of the coating were examined by Vickers hardness tester and nanoindentation tester. The friction and wear properties of the Inconel 718 coating was evaluated from 30°C to 800 °C in air against Si3N4 counterpart. Results show that the V and Cr transition layers are composed of V bcc and Cr bcc respectively, without undesirable intermetallic compounds. The Inconel 718 coating contains γ-Ni(Cr, Fe) and (Ni,Ti,Al) solid solutions as well as Ni4Nb and Ni0.45V0.55 intermetallic compounds. Due to the diffusion of V element into the Inconel 718 coating, the segregation of Nb was improved and the formation of Laves phase was inhibited. The strengthening effect of intermetallic compounds leads to a remarkable increase in the mechanical properties of the coating compared with Ti-6Al-4V substrate. The Inconel 718 coating suffers from abrasive wear and micro-cutting at low and middle temperature, while exhibits superior wear resistance due to the formation of the glazed layer at high temperature.

Ultrafast synthesis of the nanostructured Al59Cu25.5Fe12.5B3 quasicrystalline and crystalline phases by high-energy ball milling: Microhardness, electrical resistivity, and solar cell absorptance studies

In this study, the Al59Cu25.5Fe12.5B3 nanoquasicrystalline alloy and related crystalline phases were synthesized through mechanical alloying using a high-energy ball milling and consolidated by a cold isostatic pressing apparatus. This paper focuses on the synthesis, structural and microstructural evolutions, thermal stability, microhardness, and electrical and optical properties of the Al59Cu25.5Fe12.5B3 nanoquasicrystalline alloy for solar selective absorber usages. The structural evolutions of the mechanically alloyed and heat-treated AlCuFeB powders were investigated by X-ray diffractometry. Accordingly, the effect of milling time and heat treatment on the formation of quasicrystalline and related crystalline phases were studied in the AlCuFeB alloy system. The microstructure, morphology, and chemical microanalysis of the un-milled and as-milled powders were examined by field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. The composition of the as-milled AlCuFeB powders was estimated employing inductively coupled plasma-atomic emission spectroscopy. The thermal stability of the AlCuFeB powders was recorded by differential thermal analysis, and the weight gain of the particles during annealing was investigated through thermogravimetric analysis. The nanostructured Al59Cu25.5Fe12.5B3 stable quasicrystalline phase and crystalline Al(Cu,Fe) solid-solution were synthesized by the ultrafast milling procedure in 1 h. The rationale behind using the term ultrafast synthesis is to synthesize the QC i-phase only by the high-energy ball milling procedure in short-term ball milling without subsequent annealing treatment. However, the single quasicrystalline phase could not be obtained even after the annealing treatment. The quasicrystalline size was calculated by the Williamson–Hall method and optimized by the Rietveld refinement procedure, and it was found that the size is varied between 53 and 61 nm. Furthermore, the particle size distribution of the as-milled AlCuFeB powders was measured using laser static light scattering, which ranges from 0.1 to 50 μm. The microhardness of the consolidated as-milled and heat-treated samples was estimated utilizing the Vickers microhardness indenter. At the same time, their electrical resistivity was assessed by the four-point probe method at room temperature. The spectral analyses of absorption on the consolidated as-milled samples were carried out in the ultraviolet, visible, and near-infrared regions. It was found that the presence of the quasicrystalline phase in the AlCuFeB alloy prominently improves the microhardness, electrical resistivity, and particularly sunlight absorptance.

Microstructural Characteristics of AlSi9Cu3(Fe) Alloy with High Melting Point Elements

The paper presents the results of microstructure tests of EN AC-46000 hypoeutectic Al–Si alloy with and without high-melting-point elements: chromium, molybdenum, vanadium, and tungsten. The above-mentioned elements were used individually or simultaneously in various combinations. The tested castings were made using two technologies: shell molding and high pressure die casting (HPDC). Using X-ray diffraction and microanalysis of the chemical composition an attempt to determine the phase structure of the tested alloy was made. It has been shown that the microstructure of the base alloy consists of dendrites of α(Al) solid solution and complex eutectic mixtures: ternary α(Al) + Al15(Fe,Mn)3Si2 + β(Si) and quaternary α(Al) + Al2Cu + AlSiCuFeMgMnNi + β(Si). High-melting point elements, regardless of the combination used, attach mainly to intermetallic phases rich in Fe and form the Al15(Fe,Mn,M)3Si2 phase, where M is any high melting point element or a combination of such elements. It has been shown that the area fraction of the above-mentioned phase increases with increasing content of high melting point elements. A greater area fraction of the Al15(Fe,Mn,M)3Si2 phase in the casting from the shell mold in relation to the high pressure die casting has been also found.

Solid solution softening in dislocation-starved Mg–Al alloys

Here, we report molecular dynamics (MD) calculations of spall strength in pure magnesium and magnesium alloys with 1–8 at.% aluminum in solid solution. The Mg–Al solid solution alloys are found to have a weaker spall strength than pure magnesium, e.g. the spall strength of Mg-8 at.% Al is found to be 12% lower than pure magnesium. Moreover, we find that the spall strength of Mg–Al alloys monotonically decreases with increasing concentration of Al content. We term this phenomena solid solution softening (SSS) of spall strength, which is contrary to the conventional solid solution strengthening observed in most alloys (including Mg–Al alloys) deformed at quasi-static loading rates. We argue that this transition from solid solution strengthening at quasi-static rates to SSS at extreme loading rates is due to a transition from dislocation glide dominated failure at low rates to dislocation nucleation dominated failure at extreme rates. The distortion of the host lattice by solute atoms is found to retard dislocation glide, but aids dislocation nucleation. We thus conclude that SSS may manifest in any dislocation-starved system, regardless of loading rate. To this end, we propose a theoretical model for spall strength in dislocation-starved bulk and nanoporous alloys that exhibits remarkable agreement with our molecular dynamics calculations. Our theory bares some resemblance to the double kink nucleation enhancement theory for low-temperature SSS in some body centered cubic metals, e.g. refractory metals alloyed with group IV-VIII elements.

Structural Evolution in the Quenched Al–Zn–Mg–Fe–Ni Alloy during Severe Plastic Deformation and Annealing

The evolution of the structure and phase composition of the Al–Zn–Mg–Fe–Ni alloy (nikalin) during severe plastic deformation by high pressure torsion and annealing has been investigated using high-resolution TEM techniques. The deformation of the quenched alloy has been found to result in a submicron composite comprising an Al matrix and various fine aluminides. The severe structural refinement takes place along with phase transformations, which dissolve the metastable Al3Zr-phase particles and cause the nanosized strengthening phases Т (Al2Mg3Zn3) and η' (MgZn2) to precipitate from the Al solid solution which has been supersaturated in result of quenching and deformation. Nikalin has been determined to retain its submicrocrystalline state during low-temperature annealing (200°C, 4 h) due to the barrier effect of fine hardening phase particles, fixing grain boundaries. High-temperature heating to 400°C for four hours transfers nikalin to the overaged state, in which it is characterized to consist of a recrystallized matrix with grains 2–3 µm in size, eutectic micron-sized aluminides, and stable Al2Mg3Zn3 and MgZn2-phase particles with sizes of no more or equal to 500 nm.

Influence of Welding Speed on Characteristics of Non-Axisymmetric Laser-Tungsten Inert Gas Hybrid Welded Mg/Al Lap Joints with Zn Filler.

A non-axisymmetric laser-tungsten inert gas (TIG) heat source was designed to join Mg–Al dissimilar metals with pure Zn filler at a series of welding speeds (500–900 mm/min). Laser and TIG heat sources respectively acted on Al and Mg base metals to precisely control their dissolution into the welding pool. The solidification rate of liquid metal was controlled by adjusting the welding speed, then the reaction process of Mg, Al and Zn could be accurately regulated. The results indicated that various microstructures including Al solid solution, Zn solid solution, Mg–Zn intermetallic compounds (IMCs) and eutectic structure formed in the joint produced at different speeds. Lower welding speed (500 mm/min) caused the microstructure coarsening and higher welding speed (900 mm/min) would lead to the enrichment of MgZn2 intermetallic compounds. At the optimal welding speed of 800 mm/min in particular, fine MgZn2 IMCs grains uniformly distributed in the Al and Zn solid solution. The tensile-shear load reached a maximum of 1052.5 N/cm and the joint fractured at the fusion zone near the Al base metal.

Vertical continuous compound casting of copper aluminum bilayer rods

A vertical continuous compound casting technology for the production of rotationally symmetric bilayer rods consisting of brass CuZn37 and aluminum AA7075 was developed. The interface of the metallurgically bonded semi-finished products was composed of four intermetallic layers and an anomalous eutectic area of Al2Cu (θ-AlCu), Al solid solution (α-Al), and other intermetallic precipitates. The intermetallic layers were CuZn (β-CuZn), a suggested two-phase region of Al3Cu5Zn2 (τ-AlCuZn) and Cu5Zn8 (γ-CuZn), Al4Cu3Zn (τ′-AlCuZn), and AlCu (η2-AlCu). The correlation between the process parameters casting speed, cladding temperature, and tool tempering and the interface formation was studied. The experimental investigations were accompanied by a numerical FEM analysis. The casting speed and the cladding temperature were found to be key factors, that influence the formation of a cohesion between the joining partners.

Effect of inhomogeneous composition on the thermal conductivity of an Al alloy during the precipitation-hardening process

Precipitation hardening of Al alloys is an essential aging process for industrial applications demanding lightweight and high-mechanical strength materials. However, this process drastically reduces the thermal conductivity of the Al alloy owing to the formation of intermetallic precipitates. Because the growth of the intermetallic precipitates is a complicated process involving the diffusion of alloying elements as well as phase transformation, the prediction of the thermal conductivity during the precipitation process has not been accomplished. Herein, an accurate prediction method for the effective thermal conductivity of Al alloys during the precipitation process is presented. Interestingly, the study finds that the inhomogeneous distribution of the composition in the Al solid solution generates a considerably inhomogeneous distribution of the thermal conductivity around the precipitates; consequently, the accuracy of our prediction is 30% higher than that in previous studies.

Microstructure of In-Situ Friction Stir Processed Al-Cu Transition Zone

The majority of literature sources dedicated to dissimilar Al-Cu friction stir welding testifies to the formation of intermetallic compounds (IMC) according to diffusion-controlled reactions, i.e., without liquation on the Al/Cu interfaces. Fewer sources report on revealing Al-Cu eutectics, i.e., that IMCs are formed with the presence of the liquid phase. This work is an attempt to fill the gap in the results and find out the reasons behind such a difference. Structural-phase characteristics of an in-situ friction stir processed (FSP) Al-Cu zone were studied. The single-pass FSPed stir zone (SZ) was characterized by the presence of IMCs such as Al2Cu, Al2Cu3, AlCu3, Al2MgCu, whose distribution in the SZ was extremely inhomogeneous. The advancing side SZ contained large IMC particles as well as Al(Mg,Cu) solid solution (SS) dendrites and Al-Al2Cu eutectics. The retreating side SZ was composed of Al-Cu solid solution layered structures and smaller IMCs. Such a difference may be explained by different levels of heat input with respect to the SZ sides as well as by using lap FSP instead of the butt one.

Behaviour of novel low-cost blended elemental Ti–5Fe-xAl alloys fabricated via powder metallurgy

Ti alloys, generally made via wrought metallurgy, are commonly used as biomedical materials. The manufacturing of such alloys via powder metallurgy offers the possibility to reduce the cost as well as to develop innovative compositions not otherwise achievable. The aim of this study is to understand the effect that the progressive addition of Al has on the physical and mechanical behaviour of the low-cost powder metallurgy Ti–5Fe alloy for structural biomedical implants. Specifically, Ti–5Fe-xAl (x = 1–6 w.%) alloys were developed combining blending elemental and cold pressing plus vacuum sintering to further limit the manufacturing costs as Al is lighter and cheaper than Ti. This investigation demonstrates that the amount of Al added significantly changes the thermodynamics of the sintering process and induces microstructural modifications such as grain refinement. These effects jointly with the Al solid solution strengthening leads to progressively stronger and harder (but less ductile) α+β Ti alloys characterised by the typical α+β lamellar microstructure with mechanical behaviour suitable for a variety of structural biomedical implants.

Structure refinement, mechanical properties and feasibility of deformation of hypereutectic Al–Fe–Zr and Al–Ni–Zr alloys subjected to ultrasonic melt processing

Hypereutectic Al–Fe and Al–Ni alloys offer a potentially attractive combination of properties, e.g. high-temperature strength and stability, high elastic modulus and low coefficient of thermal expansion. This potential, however, cannot be reached unless the structure of these alloys is refined so that their processing becomes possible. In this study, we for the first time apply ultrasonic melt processing for refining the structure of hypereutectic Al-4% Fe and Al-8% Ni alloys with 0.3 wt% Zr addition. Both primary Al3Fe and Al3Ni particles as well as aluminum/eutectic grains are significantly refined. It is suggested that cavitation-induced fragmentation of primary Al3Zr crystals plays a significant role in the nucleation of intermetallics as well as aluminum. Furthermore, the hardness and tensile properties of the alloys substantially increase after ultrasonic treatment due to the refined structure, which also contributes to the considerably enhanced ductility of the alloys. As a result, the fracture mode changes from brittle fracture to ductile fracture. The increase in ductility makes the alloys suitable for hot deformation, which is demonstrated by lab-scale hot rolling. In addition, precipitation hardening of the alloys can be achieved by high-temperature annealing at 450 °C due to retained Zr in the Al solid solution upon solidification. The results are supported by the analysis of the composition of a supersaturated solid solution of Zr in Al and scanning and transmission electron microscopy that confirms the precipitation of coherent Al3Zr nanoparticles. It is demonstrated that a combination of ultrasonic melt processing and alloying with Zr makes it feasible to develop new class of hypereutectic casting and wrought alloys based on the Al–Fe and Al–Ni systems.

Simultaneous Improvement of Thermal Conductivity and Strength for Commercial A356 Alloy Using Strontium Modification Process

The Aluminum–Silicon (Al–Si) die-casting alloys, such as the commercial A356 alloy, are expected to be used in heat-sink and the device with high thermal conductivity due to their high production efficiency of casting process. These fields also required them to possess sound mechanical properties. To meet these demands, the Strontium (Sr) was often utilized to modify the silicon phase. According to our current work, the secondary dendrite arm spacing of the α-Al grains prominently was decreased when 0.05%–0.25% strontium was added. The decrease of the secondary dendrite arm spacing (SDAS) lead to the enhancement of the mechanical strength as well as the improvement of the thermal and electrical conductivity. When the Sr dosage was 0.15% in the commercial A356 alloy, the strength and the thermal conductivity of the A356 alloy simultaneously reached the maximum value. The improvement of the electrical and thermal conductivity might by contributed by the formation of a good conductor, Al2Si2Sr phase, on the Si surface. Further investigations suggested that the improvement of thermal conductivity was mainly due to the modification effect of Sr on the eutectic Si phase, which enlarged the specific area between the α-Al/eutectic Si interface. The WDS analysis indicated that the solubility of Si decreased in aluminum matrix by increasing in the Sr dosage. However, the excessive dosage of strontium would result in the coarsening of the modified silicon phase, deteriorating the strength and the thermal and electrical conductivity of the modified A356 alloys. In this work, the commercial A356 alloy was modified by adding small amounts of strontium (Sr). This kind of aluminum alloy with sound fluidity could be formed by using casting process, and it was potential to be applied in the structural parts. After the Sr modification, the plate-like silicon (Si) phase was transformed to fibrous shape in the raw commercial A356. Meanwhile, it was found that the content of silicon in the Al solid solution was reduced.The XRD and SEM analysis suggested that the Al2Si2Sr phase was formed on the modified silicon phase, which was favorable to the conduction of free electron.

Aging- and creep-resistance of a cast hypoeutectic Al-6.9Ce-9.3Mg (wt.%) alloy

A ternary Al-6.9Ce-9.3Mg (wt.%) hypoeutectic alloy, consisting of equal amounts of α-Al(Mg) solid-solution regions and Al(Mg)-Al11Ce3 eutectic colonies, is investigated in terms of its aging and creep resistance. The eutectic regions exhibit a microhardness of 1230 MPa, which is thrice the value of Al-Al11Ce3 eutectic regions in a binary Al-12.5Ce (wt.%) near-eutectic alloy, demonstrating that Mg in solid-solution enhances the strengthening provided by the micron-scale highly-branched Al11Ce3 phase. X-ray diffraction measurements during ambient-temperature tensile testing reveal that load is being transferred from the Al(Mg) matrix to the Al11Ce3 phase, confirming that the fine eutectic microstructure displays composite strengthening in addition to the expected precipitation- and solid-solution strengthening. The hardness remains effectively unchanged after aging at 450 °C for up to 8 weeks, indicating excellent coarsening resistance of the Al11Ce3 phase. The ternary alloy exhibits creep resistance at 300 °C slightly inferior to the near-fully eutectic binary Al-12.5Ce (wt.%) alloy, consistent with the presence of large regions of fast-creeping primary Al(Mg) solid-solution matrix between the strong Al(Mg)-Al11Ce3 eutectic colonies in the hypoeutectic ternary alloy.

Annealing-Induced Structural–Phase Transformations in an Al–Zn–Mg–Fe–Ni Alloy after High Pressure Torsion

Abstract—The evolution of the microstructure and phase composition of the eutectic Al–Zn–Mg–Fe–Ni alloy subjected to severe plastic deformation by high pressure torsion has been investigated during annealing. The deformation treatment has resulted in a composite with a nanostructured matrix, namely, an Al solid solution alloyed with zinc and magnesium, and comprising submicron Al9FeNi aluminides. The sequence and the kinetics of post-deformation processes (recovery, aging, recrystallization) during the heating of the alloy to 400°C have been established. Heating to 200°C has been shown to preserve the nanostructural state and the high hardness (1100 MPa) of the alloy due to recovery and aging processes taking place simultaneously. The tendency to recrystallization increases with increasing temperature; and static recrystallization becomes the main relaxation process accompanied by grain growth (to 30 µm) and a decrease in hardness.

Novel High-Strength Casting Al−Zn−Mg−Ca−Fe Aluminum Alloy without Heat Treatment

Based on the studies of its structure, as well as technological and mechanical properties, the composition and application prospects are substantiated for a high-strength aluminum Al–Zn–Mg–Ca–Fe casting alloy with no heat treatment. As the subjects of study, we have obtained alloys based on a composition of Al–5.5% Zn–1.5% Mg (wt %) jointly and separately alloyed with 0.5–1.0% Ca, and 0.5% Fe. As the reference, we used standard AK12M2, AMg6lch, and AM4.5Kd casting alloys corresponding to GOST (State Standard) 1583–93: by means of pencil sample casting, the alloy has been tested for the tendency to form hot cracks owing to hindered shrinkage. It is shown that separate alloying with calcium and iron does not promote any improvement of crack resistance and adversely affects mechanical properties. The combined alloying with 1% Ca and 0.5% Fe makes it possible to improve the parameter of hot tearing susceptibility to the level inherent in the AMg6lch alloy. This effect is caused by the formation of eutectic calcium-containing phases, and the formation of a favorable grain structure in which there are no columnar grains. Iron in the structure of the alloy is bound in compact particles, representing a Al10CaFe2 phase, which is a consequence of a nonequilibrium crystallization process occurring in the course of chill-mold casting. The formation of this phase makes it possible to reduce the amount of zinc in the (Al, Zn)4Ca phase and mostly to conserve the composition of the (Al) solid solution, as is indicated by similar hardness values of the base Al–5.5% Zn–1.5% Mg alloy and Al–5.5% Zn–1.5% Mg–1% Ca–0.5%–Fe alloy, as well as the superiority of these values over the hardness values of alloys separately alloyed with calcium and iron. In addition, the hardness of the promising alloy in the as-cast state is more than 20 HV higher than the hardness of branded cast alloys in the same condition. The novel alloy in the as-cast state has shown the following competitive mechanical tensile properties: σUTS ~ 310 MPa, σ0.2 ~ 210 MPa, and δ ~ 4%.

Microstructure and mechanical properties of TA1/3A21 composite plate fabricated via explosive welding

ABSTRACT The microstructure and mechanical properties of explosively welded TA1/3A21 composite plate were studied. The results suggested that the bonding interface had a wavy appearance, and two types of Ti–Al solid solutions were found in the crest region. Most of the interfaces had a thin diffusion layer with a thickness of approximately 3 µm, and no brittle intermetallic compounds were formed. The interface of the explosively welded TA1 Ti/3A21 Al composite plate exhibited reliable shear and bending properties. The propagation of the facile cracks initiated at the Ti–Al solid solution/Al interface, and the Ti–Al solid solution region at the vortex could be terminated by the Ti matrix. In addition, the complex bonding interface structure inhibited the crack propagation along the interface.

New high-strength casting aluminum alloy based on the Al–Zn–Mg–Ca–Fe system without requirement for heat treatment

The paper substantiates the composition and prospects of using high strength Al–Zn–Mg–Ca–Fe casting aluminum alloy without heat treatment based on the study on the structure, technological and mechanical properties. Alloys of the base composition Al–5.5%Zn–1.5%Mg (wt.%) jointly and separately doped with 0.5–1.0 % Ca and 0.5 % Fe were obtained as the objects of research. Standard casting alloys according to GOST 1583-93: AK12M2, AMg6lch, AM4,5Kd were the objects of comparison. A hot tensile test using a cast test bar was conducted to check the tendency to form hot cracks due to hindered contraction. It was shown that separate alloying with calcium and iron does not contribute to the improvement of crack resistance and adversely affects mechanical properties. Combined alloying with 1 % Ca and 0.5 % Fe improves the hot tearing resistance to the level of the AMg6lch alloy properties. This effect is due to calcium-containing phases of eutectic origin formed and a favorable grain structure created that is free from columnar grains. Iron in the alloy structure is bound in compact Al10CaFe2 phase particles as a result of the non-equilibrium crystallization during permanent mold casting. The formation of this phase allowed to reduce the amount of zinc in the (Al, Zn)4Ca phase and mostly retain the (Al) solid solution composition as evidenced by similar hardness values of the Al–5.5%Zn–1.5%Mg base alloy and Al–5.5%Zn–1.5%Mg–1%Ca–0.5%Fe alloy, and the superiority of the values over the hardness of alloys separately alloyed with calcium and iron. Also the cast hardness of the promising alloy more than 20 HV higher than the cast hardness of commercial cast alloys. The new alloy in the as-cast condition exhibited competitive mechanical tensile properties: UTS ~ 310 MPa, YS ~ 210 MPa, El ~ 4 %.