Al65Cu20Fe15 Alloy Research Articles

Structural Characterization of Al65Cu20Fe15 Melt-Spun Alloy by X-ray, Neutron Diffraction, High-Resolution Electron Microscopy and Mössbauer Spectroscopy.

The aim of the work was to characterize the structure of Al65Cu20Fe15 alloy obtained with the use of conventional casting and rapid solidification-melt-spinning technology. Based on the literature data, the possibility of an icosahedral quasicrystalline phase forming in the Al-Cu-Fe was verified. Structure analysis was performed based on the results of X-ray diffraction, neutron diffraction, 57Fe Mössbauer and transmission electron microscopy. Studies using differential scanning calorimetry were carried out to describe the crystallization mechanism. Additionally, electrochemical tests were performed in order to characterize the influence of the structure and cooling rate on the corrosion resistance. On the basis of the structural studies, the formation of a metastable icosahedral phase and partial amorphous state of ribbon structure were demonstrated. The possibility of the formation of icosahedral quasicrystalline phase I-AlCuFe together with the crystalline phases was indicated by X-ray diffraction (XRD), neutron diffraction (ND) patterns, Mössbauer spectroscopy, high-resolution transmission electron microscopy (HRTEM) observations and differential scanning calorimetry (DSC) curves. The beneficial effect of the application of rapid solidification on the corrosive properties was also confirmed.

Structure and corrosion resistance of Al–Cu–Fe alloys

The microstructure and electrochemical properties of Al–Cu–Fe alloys with the atomic compositions of Al65Cu20Fe15, Al78Cu7Fe15 and Al80Cu5Fe14Si1 have been studied. The alloys were produced by induction melting of pure elements with copper mold casting. The microstructure of the alloys was analyzed by X-ray diffraction and high-resolution transmission electron microscopy. The formation of quasicrystalline phases in the Al–Cu–Fe alloys was confirmed. The presence of intermetallic phases was observed in the alloys after crystallization in a form of ingots and plates. The electrochemical measurements were conducted in 3.5% NaCl solution. The electronic structure of the alloys was determined by X-ray photoelectron spectroscopy. The post corrosion surface of the samples was checked using a scanning electron microscope equipped with the energy-dispersive X-ray detector. It was observed that the Al65Cu20Fe15 alloy had the highest corrosion resistance. The improved corrosion resistance parameters were noted for the plate samples rather than those in the as-cast state. And the hardness of the Al65Cu20Fe15 alloy was significantly higher than the other alloy samples.

Spherical Particles in Al65Cu20Fe15 Alloy Prepared by Arc Melting

An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

A study on spherical particles in Al65Cu20Fe15 alloy prepared by arc melting

Al-Cu-Fe alloys are important due to reports that stable icosahedral quasicrystalline phase with composition in the vicinity of Al65Cu20Fe15 can be prepared. However, it has been widely reported that the as-prepared alloy, very often by arc-melting, is porous, consisting of particles with different morphologies. Among these, one type of particles of a spherical shape is considered as pure cubic β phase in previous reports. In this research, this spherical particle was studied using a Scanning Electron Microscope, Energy Dispersive X-ray Spectroscopy, Transmission Electron Microscope, and Electron Diffraction. It was found that the particles are not single phase, consisting of icosahedral quasicrystalline grains embedded inside single crystal matrix of τ phase. Additionally, there are places where the τ phase appears to have out-most layer enriched in Cu. The surface of the particles is faceted and the facets can be classified to three types according to their detailed structures. A close examination and analysis led to the conclusion that these three types are parallel to the atomic planes of {1 1 0}, {1 1 1}, and {1 0 0}, respectively. A model for the spherical particle formation is suggested and the reasons for the formation of facets are discussed. This report is valuable in clarifying some discrepancies in previous reports, and in understanding the phase development in an Al-Cu-Fe alloy system.

Quasicrystal as a Catalyst for the Synthesis of Carbon Nanotubes.

The present report describes the catalytic activity of mechanically activated nano quasicrystalline Al65Cu20Fe15 and related nano crystalline Al50Cu28Fe22 for the synthesis of carbon nanotubes (CNTs). CNTs are synthesized by catalytic decomposition of ethanol through nano quasicrystalline Al65Cu20Fe15 and related crystalline Al50Cu28Fe22 alloys as a catalyst. The synthesized multi-walled CNTs exhibits tube diameter ranging from 5 to 25 nm. The synthesized CNTs are characterized by scanning and transmission electron microscopy. It is found that Al65Cu20Fe15 nanoquasicystal shows better catalytic behaviour as compared to nano-crystalline Al50Cu28Fe22 alloys for decomposition of ethanol during the synthesis of multi-walled CNTs.

Application of ultrasound irradiation on sol–gel technique for corrosion protection of Al65Cu20Fe15 alloy powder

Al65Cu20Fe15 alloy powder was firstly encapsulated by the conventional sol–gel technique utilizing tetraethoxysilane (TEOS) as the precursor in order to improve its corrosion resistance. The optimization was based on nine well-planned orthogonal experiments (L9 (34)). Four main factors in the encapsulation process (i.e. reaction temperature, ethylenediamine concentration, TEOS concentration and feeding method) were investigated. According to the visual analyses of the result, the optimum condition was obtained. Based on the optimal condition in the conventional sol–gel technique, the encapsulation process was then conducted under ultrasonic irradiation. The effects of ultrasound amplitude and irradiation time on the encapsulation process were also studied. FTIR, XRD, SEM, DLS and EDS were also used to characterize the resulting sample. Finally, the corrosion inhibition efficiency of encapsulated powder attained 99.3% in the acidic condition of pH 1, and the average grain size (d50) of the encapsulated powder was just 4.8% larger than that of the raw powder, implying that there was a thin silica film on the surface of powder.

Attainment of quasicrystalline phase in Al–Cu–Fe alloy via melting and mechanical alloying

Abstract Al62Cu25.5Fe12.5 (A) and Al65Cu20Fe15 (B) alloys were fabricated via melting and experimentally studied in both as-cast and annealed conditions. Alloy (B) was also fabricated using mechanical alloying and an annealing treatment. The melted alloys were characterized to investigate the distribution of alloying elements Fe and Cu on the icosahedral and coexisting phases, as well as the hardness of all phases. The as-cast alloys showed the highest amount of icosahedral phase with up to 47% of ingot (A), but this increased after heat treatment to 99% and 75% of ingots in (A) and (B) alloys respectively. During heat treatment the iron content was increased in all phases, while the copper content decreased. As a consequence, the hardness of the icosahedral phase increased by 23% in (A) Al62Cu25.5Fe12.5 alloy and 33% in (B) Al65Cu20Fe15 alloy. On the other hand, the effect of heat treatment on samples obtained from mechanical alloying caused a modification in the iron and copper contents, leading to the formation of iron-rich phases such as λ-(Al, Cu)13Fe4 phase for all milling times and the icosahedral phase after 35 h.

Quasicrystalline phase formation during heat treatment in mechanically alloyed Al65Cu20Fe15 alloy

Quasicrystalline phase formation during heat treatment in the mechanically alloyed Al65Cu20Fe15 powders was studied by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The mechanical alloying was performed at speed of 300 rev min–1 for times up to 70 h. It was found that mechanical alloying of the Al65Cu20Fe15 powders did not result in the quasicrystalline (QC) icosahedral phase (i-phase) formation. The long time milling resulted in the formation of a cubic Al (Cu,Fe) solid solution phase (β-phase). The cubic Al (Cu,Fe) solid solution identified as β-phase was observed to be present as one of the major phases in the Al65Cu20Fe15 alloy. The formation of the quasicrystalline icosahedral phase (i-phase) was only observed for short time milled powders after additional annealing at temperature above 500°C. The present investigation also showed that a tetragonal Al2Cu phase (θ-phase) forms with short time milling. The tetragonal Al7Cu2Fe1 phase (w-phase) was observed after heat treatment of the short time milled and unmilled powders. The present investigation indicated that an effective process to prepare the quasicrystalline materials was using a combination of short time milling and subsequent annealing.

Nanocrystal Model for Liquid Metals and Amorphous Metals

A nanocrystal model for liquid metals and amorphous metals has been developed. With the nanocrystal model, the broadening peak profiles (BPPs) of Cu, Al, Al65Cu20Fe15 alloy, Cu70Ni30 alloy and Fe50Si50 alloy were gained by broadening the X-ray diffraction (XRD) peaks of a crystal lattice. By comparing the BPPs with the XRD intensity curves measured on the liquid metals, it is found that the BPPs are closely in agreement with the XRD intensity curves, respectively, except the Fe50Si50 alloy. Therefore, the nanocrystal model can be used to determine if the atomic cluster structure of the liquid metal is similar to the structure of its crystal lattice.

Nanocrystallization and structural correlation in quasicrystalline and crystalline phases during mechanical milling

Abstract The main objective of the proposed work is to investigate the formation of nanoquasicrystalline and related nanocrystalline phases in Al—Cu—Fe system during mechanical milling at the initial stage of milling. The mechanical milling of a quasicrystalline Al65Cu20Fe15 alloy was performed in a high-energy ball mill (Szegvari attritor) by varying milling time from 2.5 min to 60 min under liquid hexane medium at the speed of 400 rpm with a ball to powder ratio of 40 : 1. X-ray diffraction was carried out for evaluating the lattice strain, lattice parameters and crystallite sizes of the milled sample. It was found that the evolution of monoclinic Al13Fe4 phase from Al65Cu20Fe15 quasicrystalline phase occurred after 2.5 min of milling, which was further confirmed by transmission electron microscopy. After 5 min of ball milling nano size disordered B2 phase (bcc, a = 0.29 nm) was also found. The systematic analysis of the XRD patterns for evolving lattice parameter, sequential strain suggests that the lattice strain during milling has been quite considerable.

Characterization of the icosahedral quasicrystalline phase in rapidly solidified Al–Cu–Fe alloys

Abstract The present research aimed to characterize the microstructure of icosahedral quasicrystalline phase (i-phase) in different chemical compositions of Al–Cu–Fe alloys. The ternary alloys with the nominal compositions of Al70Cu20Fe10, Al65Cu20Fe15 and Al63Cu25Fe12 (at%) were rapidly solidified by melt-spinning technique. The melt-spun ribbons were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). According to the XRD results, diffraction patterns of Al70Cu20Fe10 alloy showed the presence of the i-phase together with tetragonal θ-Al2Cu phase. However, XRD pattern of the melt-spun Al63Cu25Fe12 alloy showed the formation of i-phase together with a small amount of β-phase. The single quasicrystalline phase was observed only in the rapidly solidified Al65Cu20Fe15 alloy. The SEM examinations showed that the melt-spun Al70Cu20Fe10 and Al63Cu25Fe12 alloys composed of i-phase with an average grain size of 1–5 μm. However, for the Al65Cu20Fe15 alloy, the quasicrystalline particles in the star-shape dendritic formations were observed. The melting point of i-phase was determined as 890 °C by DTA examinations.

Effect of Si on As-Cast Microstructure in Quasicrystalline Al-Cu -Fe Alloy

Effect of Si on the forming ability of quasicrystalline phase in Al65Cu20Fe15 alloys fabricated under conventional casting conditions has been studied using X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM). The results show that under the conventional casting conditions, it is found that the addition of certain amount of Si into the Al-Cu-Fe melts can change the formation of Al62.5Cu25Fe12.5 quasicrystals during the solidification process. Compared with Al65Cu20Fe15 alloy, Al64.5Cu20Fe15Si0.5 alloy has smaller volume fraction of β phase solidifying initially, larger volume fraction of the quasicrystal phase generating in the subsequent peritectic reaction, and larger volume fraction of ω phase solidifying finally. Both experimental results and the theory of Hume-Rothery show that addition of Si can promote the formation ability of the icosahedral quasicrystalline Al62.5Cu25Fe12.5 phase in Al-Cu-Fe alloy.

A New Model for Microstructure of Liquid Metals

A nanocrystalline model for microstructures of liquid metals isconstructed. According to the nanocrystalline model,the intensity curves of x-ray diffraction (XRD) on liquid Cu, Al andAl65Cu20Fe15 alloy are derivedby broadening the XRD peaks of these metals in some crystal structures.These broadening intensity curves are identical with the resultsmeasured by an x-ray diffractometer on these liquid metals. The presentresults indicate that the nanocrystal model may be helpful tounderstand the microstructures of liquid metals and that there is aclose correlation between the short-range orders (SROs) of these liquidmetals and some crystal lattice structures. That is, the SRO structuresof liquid Cu, Al and Al65Cu20Fe15 alloy are fcc, bcc andicosahedron, respectively.

On some discrepancies in the literature about the formation of icosahedral quasi-crystal in Al–Cu–Fe alloys

To clarify some discrepancies in the literature about the formation of icosahedral quasi-crystal (IQC) in Al–Cu–Fe alloys, microstructures, and constituent phases of Al62.5Cu25Fe12.5 and Al65Cu20Fe15 alloys were studied. Each dendritic arm of the primarily solidified λ–Al13Fe4 phase is a single crystal that possesses no definite orientation relationship with the IQC, formed by peritectic reaction (L + λ + β → IQC) or a solid-state reaction (Cu-rich phases + λ + β →?IQC). This fact disproves an assumption that λ-phase is an approximant of the IQC. Two types of cubic phase, β-phase with CsCl structure containing more Fe and τ3 phase, which is a superstructure and contains less Fe, were observed depending on the composition and thermal history of the samples.

Effect of Si addition on the formability of the icosahedral quasicrystalline phase in an Al65Cu20Fe15 alloy

The effect of Si addition on the icosahedral forming Al65Cu20Fe15 alloy was investigated. Conventional casting and melt spinning were employed with the addition of Si element. As Si was added up to 5at.% replacing the Al atoms, the volume fraction of the i-phase gradually decreased. However, with increasing Si content further up to 15at.%, an 1/1 cubic approximant phase formed instead of the i-phase. After heat treatment at 750°C for 3h, the volume fraction of the β-phase increased in an Al64Cu20Fe15Si1 alloy, while the volume fraction of the 1/1 approximant phase increased in an Al50Cu20Fe15Si15 alloy. The Al50Cu20Fe15Si15 alloy showed a relatively high hardness and fracture toughness compared to the other Si containing Al–Cu–Fe alloys.

Studies of interfaces in Al65Cu20Fe15

The study of interfaces in quasicrystalline alloys is relatively new. Apart from the change in orientation, symmetry and chemistry which can occur across homophase and heterophase boundaries in crystalline materials, we have the additional, exciting possibility of an interface between quasicrystalline and its rational approximant. High resolution electron microscopy is a powerful technique to study the structural details of such interfaces. We report the results of a HREM study of the interface between the icosahedral phase and the related Al13Fe4 type monoclinic phase in melt spun and annealed Al65Cu20Fe15 alloy.

A STUDY OF DEEP UNDERCOOLING FOR Al-Cu-Fe ICOSAHEDRAL QUASICRYSTAL

This work was undertaken to study deep underccoling of Al65Cu20Fe15 alloy melt in Al- Cu - Fe system by cyclic superheating and cooling method. By means of the denucleating technique, Al65Cu20Fe15 alloy melt has been undercooled to 98 K under its melting point, and Al - Cu - Fe icosahedral quasicrystalline ball of 6 mm in diameter was produced. Moreover,the first phase to nucleate will change with the degree of underccoling in alloy melt. It was confirmed that quasicrystal forming ability can be enhanced by increasing the level of denu-cleating in Al65Cu20Fe15 alloy.

Short-range order of quasicrystals after ball milling

Thermodynamically stable icosahedral Al65Cu20Fe15 alloy is studied using57Fe Mossbauer experiments. Its quasicrystalline structure is subjected to a low energy process of mechanical grinding up to 800 hours. The influence of ball milling on the electric field gradient magnitudes is discussed using an analysis of the Mossbauer spectra to different fitting models. The presence of an amorphous phase which co-exists with the quasicrystalline one is revealed in the early stage of mechanical grinding.

Nucleation of Al-Cu-Fe alloy in a drop tube

The undercooling and nucleation of an Al65Cu20Fe15 alloy have been investigated with a 1.2-m-long drop tube. Melted droplets solidified either in vacuum or in helium. Various size samples in the forms of a globule, a fine fiber, and an irregular splat were collected at the bottom of the tube. X-ray phase identification results indicated that the CsCl-type cubic phase with a lattice parameter of 2.94 Å and Al-Cu-Fe icosahedral quasicrystalline phase coexist in most specimens. However, the amount of each phase differs in various size samples due to the different cooling rates and undercoolings. It can be concluded that deep undercooling is beneficial to the formation of the Al-Cu-Fe icosahedral phase. In addition, in some rapidly solidified fine fibers (<105 K/S), the Al-Cu-Fe ternary amorphous phase was also observed by high resolution transmission electron microscopy.

A quasicrystalline transition state in an annealed Al65Cu20Fe15 alloy

A quasicrystalline transition state was found in an Al65Cu20Fe15 alloy after heat treatment at 700 °C and subsequent slow cooling of samples originally containing the icosahedral quasicrystalline phase. The transition state is characterized by the simultaneous presence of two types of quasicrystalline domains. Their structure can be obtained by the introduction of one-dimensional periodicity along one of the fivefold axes of the original icosahedral quasicrystal. The two types of domains differ in their period lengths which are obtained by multiplying a fundamental length of the icosahedral structure by the Fibonacci numbers 5 and 8.