This chapter begins with pure aluminium and a discussion of the form of the crystal structure and different unit cells that can be used to describe the crystal structure. Measurements of the face-centred cubic lattice parameter and thermal expansion coefficient in pure aluminium are reviewed and parametrisations given that allow the reader to evaluate them across the full range of temperatures where aluminium is a solid. A new concept called the vacancy triangle is introduced and demonstrated as an effective means for determining vacancy concentrations near the melting point of aluminium. The Debye-Waller factor, quantifying the thermal vibration of aluminium atoms in pure aluminium, is reviewed and parametrised over the full range of temperatures where aluminium is a solid. The nature of interatomic bonding and the history of its characterisation in pure aluminium is reviewed with the unequivocal conclusion that it is purely tetrahedral in nature. The crystallography of aluminium alloys is then discussed in terms of all of the concepts covered for pure aluminium, using prominent alloy examples. The electron density domain theory of solid-state nucleation and precipitate growth is introduced and discussed as a new means of rationalising phase transformations in alloys from a crystallographic point of view.
The composition, crystal structure and precipitation crystallography of a newly found precipitate are characterized by a Cs-corrected scanning transmission electron microscopy (STEM). The composition of the plate-like precipitate could be expressed as MgxAl2-xGd (x = 0.38), and its crystal structure is the same as the fcc type Laves phases Mg2Gd and Al2Gd with the lattice parameter of 7.92 Angstrom (space group No. 227, Fd-3m). The orientation relationship between the matrix and precipitate is found to be (0001)m // (111)p and [10-10]m // [1-10]p, and the habit plane is parallel to (0001)m // …
We discuss hydrogen diffusion and solubility in aluminum alloyed Fe-Mn alloys. The systems of interest are subjected to tetragonal and isotropic deformations. Based on ab initio modelling, we calculate solution energies, then employ Oriani's theory which reflects the influence of Al alloying via trap site diffusion. This local equilibrium model is complemented by qualitative considerations of Einstein diffusion. Therefore, we apply the climbing image nudged elastic band method to compute the minimum energy paths and energy barriers for hydrogen diffusion. Both for diffusivity and solubility of…
MnMX (M = Co or Ni, X = Si or Ge) alloys, experiencing structural transformation between Ni2In-type hexagonal and TiNiSi-type orthorhombic phases, attract considerable attention due to their potential applications as room-temperature solid refrigerants. Although lots of studies have been carried out on how to tune this transformation and obtain large entropy change in a wide temperature region, the crystallography of this martensitic transformation is still unknown. The biggest obstacle for crystallography investigation is to obtain a bulk sample, in which hexagonal and orthorhombic phases coe…
Precipitation kinetics of Al3Zr and Al3Sc in aluminum supersaturated solid solutions is studied using cluster dynamics, a mesoscopic modeling technique which describes the various stages of homogeneous precipitation by a single set of rate equations. The only parameters needed are the interface free energy and the diffusion coefficient which are deduced from an atomic model previously developed to study the same alloys. A comparison with kinetic Monte Carlo simulations based on the vacancy diffusion mechanism shows that cluster dynamics correctly predicts the precipitation kinetics provided a …
The microstructure, mechanical properties, and corrosion behavior of friction stir welded (FSW) AA6061 aluminum alloys were investigated. Dynamic recrystallized structures were observed and grain sizes of nugget zone (NZ), thermomechanically-affected zone (TMAZ), heat-affected zone (HAZ), and base material (BM) were different. Hardness test indicated that the minimum and maximum hardness values wereobtained in the HAZ and BM, respectively. Tensile results showed that fracture occurred in the relatively weak regions in between TMAZ and HAZ. Polarization tests illustrated that the FSW process im…
We use first principles calculations to study the influence of thermomechanical loads on the energetics of precipitation in magnesium-aluminum alloys. Using Density Functional Theory simulations, we present expressions of the energy of magnesium-aluminum binary solid solutions as a function of concentration, strain and temperature. Additionally, from these calculations, we observe an increase in equilibrium volume (and hence the equilibrium lattice constants) with the increase in concentration of magnesium. We also observe an increase in the cohesive energy of solutions with increase in concen…
Fracture in aluminum alloys with precipitates involves at least two mechanisms, namely, ductile fracture of the aluminum-rich matrix and brittle fracture of the precipitates. In this work, a coupled crystal plasticity-phase field model for mixed ductile-brittle failure modes is formulated and used to investigate the effect of precipitate morphology and size distribution on damage evolution in aluminum alloys. A thermodynamically consistent framework for elastic and plastic work dissipation in the fracture process zone is used to formulate the coupled constitutive behavior for brittle and ducti…
Spinning of a common aluminum automotive casting alloy A356 (Al-7Si-0.3 Mg) at elevated temperatures has been investigated experimentally with a novel industrial-scale apparatus. This has permitted the implementation of a fully coupled thermomechanical finite element model aimed at quantifying the processing history (stress, strain, strain-rate and temperature) and predicting the final geometry. The geometric predictions of this model have been compared directly to the geometry of the workpieces obtained experimentally. This study is novel in regards to both the size and shape of the component…
Experimental investigations on the effect of thicknesses on mixed-mode I/II fracture are performed with an aluminum alloy with thicknesses of 2, 4, 8 and 14 mm. It is found that under pure-mode I loading condition, the loading capacity per unit thickness monotonically decreases with increasing thickness. However, under mixed-mode loading condition, the dependence of loading capacity on the thickness becomes very weak. Although the measured crack initiation angles from the mid-plane of the fractured specimens coincide well with typical existed criteria in the thin and thick specimens under all …
Nanoindentation is a powerful tool capable of providing fundamental insights of material elastic and plastic response at the nanoscale. Alloys at nanoscale are particularly interesting as the local heterogeneity and deformation mechanism revealed by atomistic study offers a better way to understand hardening mechanism to build a stronger material. In this work, nanoindentation in Al-Cu alloys are studied using atomistic simulations to investigate the effects of loading direction, alloying percentages of Cu via dislocation-driven mechanisms. Also, a low-fidelity finite element (FE) model has be…
Surface bubbling and helium retention of pure aluminum and a solid solution of aluminum-gallium(Ga) alloy exposed to low-energy He plasma has been investigated with the fluence of 1.8E24 He/m2 at room temperature . Surface morphology observations show that after irradiation, the average size of He bubbles on Al-1.8 at.% Ga alloy is around 1.8 micro metre, smaller than that on pure Al. Ga doping noticeably increases the area density of the bubble. The thermal desorption spectroscopyshows that the release amount of He in Al-1.8 at.% Ga alloy is 1.77E21 He/m2, nearly three orders of magnitude hig…
Ultrafine-grained aluminum alloys offer interesting multifunctional properties with a combination of high strength, low electrical resistivity, and low density. However, due to thermally induced grain coarsening, they typically suffer from an intrinsic poor thermal stability. To overcome this drawback, an Al-2%Fe alloy has been selected because of the low solubility of Fe in Al and their highly positive enthalpy of mixing leading to the formation of stable intermetallic particles. The two-phase alloy has been processed by severe plastic deformation to achieve simultaneously submicrometer Al gr…
The bcc-based Fe_{1-x}Al_{x} exhibit interesting magnetic and anomalous structural properties as a function of composition and sample processing conditions arising from thermal or off-stoichiometric chemical disorder, and, although well studied, these properties are not understood. In stoichiometric B2 FeAl, including the effects of partial long-range order (i.e., thermal antisites), we find the observed paramagnetic response (with non-zero local moments), in contrast to past investigations which find ferromagnetism based on local density approximation (LDA) to density functional theory or whi…
With the rapid development of artificial intelligence, the combination of material database and machine learning has driven the progress of material informatics. Because aluminum alloy is widely used in many fields, so it is significant to predict the properties of aluminum alloy. In this thesis, the data of Al-Cu-Mg-X (X: Zn, Zr, etc.) alloy are used to input the composition, aging conditions (time and temperature) and predict its hardness. An ensemble learning solution based on automatic machine learning and an attention mechanism introduced into the secondary learner of deep neural network …
A variety of chromate-free conversion coatings are being actively investigated to improve the corrosion performance of light-weight alloys for aerospace and defense applications. Advancing conversion coating, however, requires an in-depth understanding of the underlying corrosion mechanisms in order to rationally design sustainable coatings. Here, we present a multiscale modeling approach to predict corrosion performance of metallic materials, with a focus on localized corrosion of Cu-containing aluminum alloys coated with ZrO2 layer. First-principles and transition-state theory are used to im…
Site-specific atom probe tomography (APT) from aluminum alloys has been limited by sample preparation issues. Indeed, Ga, which is conventionally used in focused-ion beam (FIB) preparations, has a high affinity for Al grain boundaries and causes their embrittlement. This leads to high concentrations of Ga at grain boundaries after specimen preparation, unreliable compositional analyses and low specimen yield. Here, to tackle this problem, we propose to use cryo-FIB for APT specimen preparation specifically from grain boundaries in a commercial Al-alloy. We demonstrate how this setup, easily im…
Modified Yukawa's potential is used to fit model parameters of nucleus to the small angle thermal neutron scattering data on the nickel-chromium-aluminum alloy at the transferred momentum $Q$ and effective nucleus radius $R$ production satisfied by condition $Q R \le \hbar$. Analytical polydisperse sphere model is used to calculate a neutron scattering intensity and to determine most probable macroscopic sphere radius $R_0$ at $Q R_0 \ge 3\hbar$. Combination of gauss, Relay and Schulze-Zimm distributions can be used to fit model parameters to experimental data. Fast algorithm and program of fi…
The electrochemical behavior and mechanical properties of friction stir welded AA5086 and AA6061 Al alloys were investigated. Micro-hardness measurements and tensile tests showed that the heat-affected zone (HAZ) in AA6061 had minimum hardness value (i.e., 88 HV) and served as failure site in the dissimilar weld. Corrosion testing revealed that the minimum value of Icorr appeared in the HAZ 5086 (0.54 uA/cm2) and HAZ 5086 was most resistant to corrosion. The AA 5086 side of the weld showed better corrosion resistance than the AA 6061 side.
In the present investigation, a strongly bonded strip of an aluminium-magnesium based alloy AA5086 is successfully produced through accumulative roll bonding (ARB). A maximum of up to eight passes has been used for the purpose. Microstructural characterization using electron backscatter diffraction (EBSD) technique indicates the formation of submicron sized (~200-300 nm) subgrains inside the layered microstructure. The material is strongly textured where individual layers possess typical FCC rolling texture components. More than three times enhancement in 0.2% proof stress (PS) has been obtain…
A multiple scattering formulation for the electromigration wind force on atoms in dilute alloys is developed. The theory describes electromigration via a vacancy mechanism. The method is used to calculate the wind valence for electromigration in various host metals having a close-packed lattice structure, namely aluminum, the noble metals copper, silver and gold and the $4d$ transition metals. The self-electromigration results for aluminum and the noble metals compare well with experimental data. For the $4d$ metals small wind valences are found, which make these metals attractive candidates f…
We report on the fabrication of fractal dendrites by laser induced melting of aluminum alloys. We target boron carbide (B4C) that is one of the most effective radiation-absorbing materials which is characterised by a low coefficient of thermal expansion. Due to the high fragility of B4C crystals we were able to introduce its nanoparticles into a stabilization aluminum matrix of AA385.0. The high intensity laser field action led to the formation of composite dendrite structures under the effect of local surface melting. The modelling of the dendrite cluster growth confirms its fractal nature an…
Aluminum and their alloys, after careful treatments, can develop excellent mechanical, tribological, electrical and chemical (high corrosion resistance) properties. However, 7000 series, with Cu in the alloy, have a poor corrosion resistance. On the other hand, aluminum nitride (AlN) has a wurtzitic phase and good thermal stability, optical, electric, piezoelectric, mechanical, tribological, and chemical properties, so the application range is huge. In this paper, AlN deposition on Al 7075 was done using the reactive magnetron sputtering technique in order to verify the aluminum nitride perfor…
NPs are ultrafine-grain crystal or amorphous substances which are as small as 100nm. They have unique physical, chemical and mechanical properties, which are very different from those of large scale materials. This uniqueness is attributed to the fact that the number of atoms in the surface layer and in the bulk is commensurable. As the atoms in the surface layer of nanoparticles have their counterparts from one side only, their balance is impaired, and the resulting structure relaxation leads to the displacement of atomic spacing in a 2-3nm layer. Therefore the surface layers expand while int…
Plasma electrolytic oxidation (PEO) is a process for obtaining oxide coatings on valve metals. Mostly PEO is done in an aqueous solution electrolyte which limits the size of treated parts due to the system heating up. In presented work an alternative method of PEO processing applied in aluminum 1050 alloy in nitrate molten salt was investigated. The morphology, phase and chemical compositions, micro-hardness, and corrosion resistance were examined using. The obtained results showed that formed coating contains from two sub-layers, outer soft layer with the thickness of 4 micrometer and inner, …
An Al-11.3Li-0.11Sc (at. %) alloy was double-aged to induce first alpha'-Al3Sc and then delta'-Al3Li precipitates. Atom-probe tomography revealed both single-phase delta'-precipitates and core-shell alpha'/delta'-precipitates (with respective average radii of 16 and 27 nm, and respective volume fractions of 12 and 9%) conferring a high strength to the alloy. Although the delta'-shells contain little Sc (~0.027 at. %), the alpha'-cores have a high Li content, with an average composition of Al0.72(Sc0.17 Li0.11). The Li concentrations within the delta'-phase and the Li interfacial excess at the …
In this research a novel and simple electrochemical method is developed in order to facilitate the large-scale production of nanowires. The proposed electrochemical technique shows versatile controllability over chemical composition and crystalline structure of Cu-Sn nanowires. Another important factor, which could be controlled by using this method, is the order structure of nanowires more accurately in comparison to conventional synthesizing procedures. As a result, the Cu-Sn nanowires as well as Aluminum Oxide templates synthesized by using the proposed electrochemical method are examined d…
ANN (Artificial Neural Networks) modeling methodology was adopted for predicting mechanical properties of aluminum cast composite materials. For this purpose aluminum alloy were developed using conventional foundry method. The composite materials have complex nature which posses the nonlinear relationship among heat treatment, processing parameters, and composition and affects their mechanical properties. These nonlinear relation ships with properties can more efficiently be modeled by ANNs. Neural networks modeling needs sufficient data base consisting of mechanical properties, chemical compo…
First-principles electronic-structure computes the lattice and elastic constants of single-crystal TiB and NbB and changes with Nb, Ti, Al, and V solutes. The data is built into an interpolation formula for lattice and elastic constants of the quartenary (TiNbAlV)B with dilute Al and V concentrations. The lattice and elastic constants of borides in two Ti alloys containing Nb and Al are predicted from microprobe measurements.
Novel ohmic contacts to n-ZnSe are demonstrated using single crystal Al films deposited on epitaxially grown ZnSe (100) by molecular beam epitaxy (MBE). Electron Backscatter Diffraction (EBSD) confirmed the single crystalline structure of the Al films. The (110)-oriented Al layer was rotated rotated 45$^\circ$ relative to substrate to match the ZnSe (100) lattice constant. The as-grown Al-ZnSe contact exhibited nearly ideal ohmic characteristics over a large doping range of n-ZnSe without any additional treatment. The contact resistances are in a range of 10$^{-3}$ $Ω$-cm$^{2}$ for even lightl…
Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and Al3Sc which for low supersaturations of the solid solution have the L12 structure. The aim of the present study is to model at an atomic scale this kinetics of precipitation and to build a mesoscopic model based on classical nucleation theory so as to extend the field of supersaturations and annealing times that can be simulated. We use some ab-initio calculations and experimental data to fit an Ising model describing thermodynamics of the Al-Zr and Al-Sc systems. Kinetic behavior is described by means of an atom-vacancy …
Machine learning is changing how we design and interpret experiments in materials science. In this work, we show how unsupervised learning, combined with ab initio modeling, improves our understanding of structural metastability in multicomponent alloys. We use the example case of Al-O-N alloys where the formation of aluminum vacancies in wurtzite AlN upon the incorporation of substitutional oxygen can be seen as a general mechanism of solids where crystal symmetry is reduced to stabilize defects. The ideal AlN wurtzite crystal structure occupation cannot be matched due to the presence of an a…
The chemical enrichment/ordering of solute atoms in Mg matrix are crucial to understand the formation mechanism of long-period stacking ordered (LPSO) structures. In this study, three-dimensional distribution of solute elements in an Mg-Zn-Gd alloy during ageing process is quantitatively characterized by three-dimensional atom probe (3DAP) tomography. Based on the radius distribution function, it is found that Zn-Gd solute pairs in Mg matrix appear mainly in two peaks at early stage of ageing and the separation distance between Zn and Gd atoms is well rationalized by the first-principles calcu…
The study of the Cu-Sn-In ternary system has become of great importance in recent years, due to new environmental regulations forcing to eliminate the use of Pb in bonding technologies for electronic devices. A key relevant issue concerns the intermetallic phases which grow in the bonding zone and are determining in their quality and performance. In this work, we focus in the η-phase (Cu2In or Cu6Sn5) that exists in both end binaries and as a ternary phase. We present a neutron diffraction study of the constitution and crystallography of a series of alloys around the 60 at.% Cu composition, an…
Enhancing Corrosion Resistance of Aluminum Alloys Through AI and ML Modeling
Research Fellow, The Washington Institute for STEM Entrepreneurship and Research（华盛顿STEM创业与研究研究所研究员）；Research Fellow, The Washington Institute for STEM Entrepreneurship（华盛顿STEM创业与研究研究所研究员）；The Washington Institute for STEM Entrepreneurship（华盛顿STEM创业与研究研究所）；Naval Nuclear Laboratory, West Mifflin, PA 15122, USA（海军核实验室）
Microstructure-property relationships of resistance spot welded 6061-T6 aluminum alloy lap joints were investigated via mechanical testing and microscopy techniques. Quasi-static tensile and novel shear punch tests were employed to measure the mechanical properties of the distinct weld regions. Quasi-static tensile and shear punch tests revealed constantly decreasing strength and ductility as the weld center was approached. For instance, the ultimate tensile strength of the fusion zone decreased by ~52% from the parent material (341 MPa to 162 MPa) while the yield strength decreased by ~62% (3…
The possibility of solid solution formation in high entropy alloys (HEAs) has been calculated for alloys with four to seven elements, using a rule previously reported. Thirty elements were included: transition elements of the fourth, fifth and sixth periods of the periodic table, and aluminum. A total of 2,799,486 systems were analyzed. The percentage of solid solutions that would be formed in HEAs decreases from 35.9% to 26.4%, as the number of elements increases from four to seven. The structure of the solid solutions, fcc, bcc or a mixture of fcc and bcc, that would be formed, has been pred…
Accurately determining the crystallographic structure of a material, organic or inorganic, is a critical primary step in material development and analysis. The most common practices involve analysis of diffraction patterns produced in laboratory XRD, TEM, and synchrotron X-ray sources. However, these techniques are slow, require careful sample preparation, can be difficult to access, and are prone to human error during analysis. This paper presents a newly developed methodology that represents a paradigm change in electron diffraction-based structure analysis techniques, with the potential to …
Functionally graded materials (FGMs), have drawn considerable attention of the worldwide researchers and scientific community because of its unique mechanical, thermal and electrical properties which may be exploited by varying the compositions gradually over volume. This makes FGM multifunctional material (properties changing continuously in a certain direction) for specific purpose without creating any phase interface thus making it superior to its composite counterparts. In this paper, we applied Molecular Dynamics (MD) approach to investigate the mechanical properties of functional graded …
Dislocation velocities and mobilities are studied by Molecular Dynamics simulations for edge and screw dislocations in pure aluminum and nickel, and edge dislocations in Al-2.5%Mg and Al-5.0%Mg random substitutional alloys using EAM potentials. In the pure materials, the velocities of all dislocations are close to linear with the ratio of (applied stress)/(temperature) at low velocities, consistent with phonon drag models and quantitative agreement with experiment is obtained for the mobility in Al. At higher velocities, different behavior is observed. The edge dislocation velocity remains dep…
High-entropy alloys (HEAs) are a new class of materials constructed from multiple principal elements statistically arranged on simple crystallographic lattices. Due to the large amount of disorder present, they are excellent model systems for investigating the properties of materials intermediate between crystalline and amorphous states. Here we report the effects of systematic isoelectronic replacements, using Mo-Y, Mo-Sc, and Cr-Sc mixtures, for the valence electron count 4 and 5 elements in the BCC Ta-Nb-Zr-Hf-Ti high entropy alloy (HEA) superconductor. We find that the superconducting tran…
An anisotropic equation of state is proposed for accurate extrapolation of high-pressure shock Hugoniot states to other thermodynamics states for shocked single crystals and polycrystalline alloys. The proposed equation of state represents mathematical and physical generalization of the Mie-Grüneisen equation of state for isotropic material and reduces to this equation in the limit of isotropy. Using an anisotropic nonlinear continuum framework and generalized decomposition of a stress tensor [Int. J. Plasticity \textbf{24}, 140 (2008)], the shock waves propagation along arbitrary directions i…
