Light Metal Alloys Research Articles

Effect of Electrolyte Concentration and Voltage on the Morphology and Corrosion Resistance of PEO Coated AA6061

Aluminum and its alloys are among the most extensively used materials in aerospace and industrial applications owing to its high specific strength, low density, and high abundance on the earth’s crust. However, low hardness, high tendency to adhesion, high corrosion, and poor wear resistance limits its further application. Surface treatments like electroplating, PVD/CVD, and anodizing are proposed to form a protective coating on the surface of Al and its alloys. Plasma Electrolytic Oxidation (PEO), known as micro-arc oxidation (MAO), emerged as a promising surface coating technique producing high-quality ceramic coating for light metal alloys like Al, Mg, Ti, and their alloys. PEO is similar to conventional anodizing but at a higher voltage exceeding its breakdown voltage, forming plasma discharge. In this study, the PEO of AA6061 was carried out in an AC power source at constant voltage 325-400 V, 1000 Hz, and 80 % duty cycle for 30 min. Silicate-based electrolytes of different concentrations (5-10 g/L) Na2SiO3 and (5-10 g/L) KOH were utilized, maintaining 25-40°C electrolyte temperature. The effect of electrolyte concentration and constant voltage on the coating morphology and its relation to hardness were investigated. Surface morphology, cross-section, elemental distribution, and phase composition were characterized using SEM, EDX, and XRD. Different breakdown voltages were determined for each electrolyte concentration. A lower breakdown voltage was achieved at a higher concentration. Porous with pancake-like structure, crater, and nodular structures were observed with coating thickness ranges from 8.37-87.33µm. α-alumina and Ƴ-alumina peaks were detected in all surface coatings.

DFT-generated scattering factors for IAMs and slabs in QCBED in light metal alloy determinations

DFT-generated scattering factors for IAMs and slabs in QCBED in light metal alloy determinations

Effect of friction stir welding parameters on microstructure and mechanical properties of the dissimilar alloys of AZ91D and AA7075

Friction stir welding is an efficient joining process for light metal alloys, offering benefits such as high joint efficiency and reduced grain sizes. This work is to investigate the process parameters that can improve the welding quality and reduce the brittle intermetallic compounds, including Al3Mg2 (β) and Al12Mg17 (γ) in the welded region. It was perceived that the process parameters influenced the morphological characteristics and input heat, thereby affecting the materialization of intermetallic compounds. The primary diffraction peaks of both Al and Mg were present in all the joints. Two specific intermetallic phases, Al3Mg2 and Al12Mg17, were formed as a result of the diffusion of Al and Mg atoms during welding. These intermetallic compounds were found in all the joints. The Al12Mg17 phase, when mixed with the Mg phase, tended to migrate towards the weld surface where the AZ91D plate was positioned. This migration might lead to constitutional liquation, which refers to the melting of specific phases during solidification, resulting in the materialization of eutectic microstructures. The highest ultimate tensile strength (UTS) value of 116.64 MPa was achieved with a rotational tool speed of 800 r/min and a traverse speed of 20 mm/min. On the other hand, the lowest UTS value of 68.32 MPa was observed with a rotational tool speed of 400 r/min and a traverse speed (TS) of 20 mm/min. It was noted that lower UTS values were associated with the materialization of dense layers of intermetallic compounds (Al12Mg17 and Mg + Al12Mg17) in the stir zone when using lower rotational tool speed and TS. It suggests that improper processing parameters can lead to the materialization of intermetallic compound in the stir zone, which subsequently decreases the mechanical properties of the weldments.

Study on mechanical characteristics of stir cast Al ADC12/B4C metal matrix composite

Automobile parts with ferrous components have been replaced by light metal alloys and their composites to minimize the pollution impact and enhance the safe environment. Al ADC12 alloy with various weight percentages (2%, 4% and 6%) of Boron Carbide (B4C) particles was cast in the stir-casting route. The mechanical characteristics of the composite samples were evaluated with tensile and wear tests. The uniform distribution of B4C with Al ADC12 composite due to the stirring action implies relatively improved results compared with base aluminium alloy. However, the composition of 6% B4C composite produces a considerable result on tensile strength and wear resistance. The stirring action of the casting process enhances the better distribution of reinforcements with matrix elements; it reveals the improvement in tensile properties and wear resistance of the composites.

Discovery of Guinier-Preston zone hardening in refractory nitride ceramics

Traditional age hardening mechanisms in refractory ceramics consist of precipitation of fine particles. These processes are vital for widespread wear-resistant coating applications. Here, we report novel Guinier-Preston zone hardening, previously only known to operate in soft light-metal alloys, taking place in refractory ceramics like multicomponent nitrides. The added superhardening, discovered in thin films of Ti-Al-W-N upon high temperature annealing, comes from the formation of atomic-plane-thick W disks populating {111} planes of the cubic matrix, as observed by atomically resolved high resolution scanning transmission electron microscopy and corroborated by ab initio calculations and molecular dynamics simulations. Guinier-Preston zone hardening concurrent with spinodal decomposition is projected to exist in a range of other ceramic solid solutions and thus provides a new approach for the development of advanced materials with outstanding mechanical properties and higher operational temperature range for the future demanding applications.

Reconstruction of dendritic growth by fast tomography and phase field filtering

Three dimensional models of dendritic structures during solidification are valuable for building physical models, validating simulated results, estimating some properties such as permeability in the mushy, simulating semisolid deformation and so on. Thus, it is of interest to observe microstructure evolution in situ. Time-resolved tomography combined with X-ray diffraction has allowed us to observe the evolution of dendritic structures and to measure crystallographic orientation in situ. Reconstruction still proves to be difficult for some alloy systems because of the tradeoff between time and spatial resolution. This paper demonstrates the reconstruction of dendritic structures for three different alloy systems (Al-10mass%Cu alloy with a diameter of 4 mm, CrMnFeCoNi alloy with 1 mm, and Zn-4mass%Al alloy with 0.7 mm). The observations were performed in a synchrotron radiation facility SPring-8. A filter using a phase field model was introduced to reconstruct the three-dimensional images. Parameters used in the filtering were consistently determined based on the raw reconstruction images. Evaluation of solid-liquid interface area and curvature was significantly improved by the filter. For the Al-Cu alloy, a three-dimensional model containing approximately 300 million voxels was obtained. For the CrMnFeCoNi alloys, the preferred growth direction <100> was confirmed by tomography and X-ray diffraction. For the Zn-Al alloy, the observed 14 growth directions were not simply defined by the crystallographic orientations, although the directions were consistent with the hexagonal symmetry. This study verifies that time resolved tomography, X-ray diffraction and the filter using a phase field model provide three dimensional models for light metal alloys with rather large diameters and 3d transition-metal alloys with rather large X-ray absorption coefficients. The models are expected to be used for further studies.

Mechanistic origins of corrosion protection of aluminum alloys by graphene/polyetherimide nanocomposite coatings

Light-weighting vehicular components through adoption of light-metal structural alloys holds promise for reducing the fuel consumption of internal combustion engine vehicles and increasing the range of battery electric vehicles. However, the alloyed microstructure and surface precipitates of aluminum alloys render these materials susceptible to corrosion under modest excursions from neutral pH. Traditional chromium-based anodic passivation layers are subject to increasingly stringent environmental regulations, whereas options for sacrificial cathodic films are sparse for electropositive metals. While hybrid nanocomposite coatings have shown initial promise, mechanistic underpinnings remain poorly understood. Here, a fully imidized polyetherimide (PEI) resin is utilized as the continuous phase with inclusion of unfunctionalized exfoliated graphite (UFG). A comprehensive investigation of the mechanisms of corrosion protection reveals key fundamental design principles underpinning corrosion inhibition. First, strong interfacial adhesion, which for PEI is facilitated by binding of imide carbonyl moieties to Lewis acidic sites on Al surfaces. Second, the miscibility of ion-impervious nanoscopic UFG fillers and stabilization of a substantial interphase region at UFG/PEI boundaries that result in minimizing the free volume at the filler/polymer interface. Finally, extended tortuosity of ion diffusion pathways imbued by the below-percolation-threshold 2D fillers. These three design principles help govern and modulate ion transport from electrolyte/coating interfaces to the coating/metal interface and are crucial for the extended preservation of barrier properties. The results suggest an approach to systematically activate multiple modes of corrosion inhibition through rational design of hybrid nanocomposite coatings across hard-to-abate sectors where light metal alloys are likely to play an increasingly prominent role.

Capability Analysis of AZ91D Magnesium Alloy Precision Milling Process with Coated Tools.

Process capability analysis is the main tool of statistical process control. It is used for the ongoing monitoring of product compliance with imposed requirements. The main objective and novelty of the study were to determine the capability indices for a precision milling process of AZ91D magnesium alloy. Machining was performed in terms of variable technological parameters and using end mills with protective TiAlN and TiB2 coatings intended for the machining of light metal alloys. The Pp and Ppk process capability indices were determined based on the measurements of the dimensional accuracy of the shaped components that were taken on a machining centre with a workpiece touch probe. Obtained results demonstrated that the type of tool coating and variable machining conditions had a significant impact on the machining effect. The selection of appropriate machining conditions enabled a terrific level of capability to be achieved at a tolerance of 12 µm, several times lower than under unfavourable conditions where the tolerance was up to 120 µm. Improvements in process capability are mainly achieved by adjusting the cutting speed and feed per tooth. It was also shown that process estimation based on improperly selected capability indices might lead to an overestimation of the actual process capability.

The influence of tool rotational speed on microstructure and mechanical performance of dissimilar FSLW

FSLW is a novel solid-sate joining process in aircraft assembly technology that has offered superior welding quality to the joining of aluminum alloy. Concerning the success of FSLW light metal alloys coupled with lower operating costs due to improved energy efficiency and virtual lack of a consumable has emphasized the need to examine AA 2024-T4 and AA 7075-T6 based on different tool rotational speeds (RSs). This research examined the three important determinants of FSLW: cross-section morphology, microstructure behavior, and mechanical performance (lap shear failure load and fracture location) to realize the quality and reasonable experiment of the welding technique. The cross-section of the lap joint is investigated in this experiment; it is evident that the maximum temperature is found in the stir zone, and the shape looks like a bowl type. Further, it is found that tool RS does not have an influence on the effective sheet thickness, but it influences the effective lap width. With the increased RS, the effective lap width increased first and then decreased. Concerning grain size analysis, the bigger grain size was observed in the heat-affected zone, and the smaller grain size was observed in the thermomechanical-affected zone. According to the mechanical performance analysis, the lap shear failure load increased and then reduced with increased RS.

Exact shell solutions for conical springs. II. Radial cylindric curb

Actual manuscript examines the disk springs with constant material thickness. The kinematic hypothesis is used for modelling. Motivating feature is the possibility to calculate the disk springs of with free gliding edges and the edges with the constrained radial movement. Variation formulations are used for derivation. The developed equations are suitable for springs made of isotropic materials, as spring steel and light metal alloys. The advantage of the methodology is the derivation of closed form solutions with restrictions on radial movement of inner and outer edges. The developed formulas are recommended for industrial calculations of free and restricted Belleville washers.

Recent advances in friction stir welding and processing of light metal alloys

Recent advances in friction stir welding and processing of light metal alloys

Metallic Materials for Hydrogen Storage—A Brief Overview

The research and development of materials suitable for hydrogen storage has received a great deal of attention worldwide. Due to the safety risks involved in the conventional storage of hydrogen in its gaseous or liquid phase in containers and tanks, development has focused on solid-phase hydrogen storage, including metals. Light metal alloys and high-entropy alloys, which have a high potential for hydrogen absorption/desorption at near-standard ambient conditions, are receiving interest. For the development of these alloys, due to the complexity of their compositions, a computational approach using CALPHAD (Calculation of Phases Diagrams) and machine learning (ML) methods that exploit thermodynamic databases of already-known and experimentally verified systems are being increasingly applied. In order to increase the absorption capacity or to decrease the desorption temperature and to stabilize the phase composition, specific material preparation methods (HEBM—high-energy milling, HPT—high-pressure torsion) referred to as activation must be applied for some alloys.

DESIGN OF LIGHTWEIGHT ELECTRIC VEHICLE AND APPLICATION FOR EFFICIENCY CHALLENGE MARATHON COMPETITION

Many vehicle manufacturers have started up the development and production of electric vehicles reducing in response to climate change, increasing air pollution and exhaust emission problems. In addition, the most important of the difficult problems associated with electric vehicles is the high cost caused by the use of a large number of batteries and the use of a limited number of batteries negatively affects the driving distance of the car. The limitations caused by the battery problems are not only to increase the cost but also increase vehicle load because it takes up too much space and limits the usage area of the vehicle. In order to address these problems, electric vehicle manufacturers have tried to find a way to reduce the weight of the vehicle body. Therefore, to reduce weight, it would be more accurate to use light metal alloys that could get better results than using polymer composites in this study 6063 series aluminum alloy box and tube profiles were used as chassis materials, and birdcage chassis production was carried out by combining these profiles with MIG welding. After production is completed, the steering system, brake system, suspension system and other moving parts are installed on the chassis. As a result, the final weight of the vehicle was 210 kg and the negativity that may occur was prevented.

Light Metal Alloys Local Reactivity, from AFM Based Scanning Kelvin Probe Force Microscopy (AFM-SKPFM) to Scanning Electrochemical Nanocapillary (SEN)

Materials surface heterogeneities obviously plays a crucial role in reactivity issues and generate various types of detrimental localized corrosion attacks. In corrosion science, a first question to be addressed is how these various materials microstructure affect oxidation / passivation and localized corrosion initiation mechanisms. A methodology for microscale characterization of initial stage of surface reactions has been developed based on the Atomic Force Microscopy (AFM) Scanning Kelvin Probe Force Microscopy (AFM-SKPFM). In very early work, potential mapping with micrometer lateral resolution (lateral detection limit of materials surface heterogeneities is better but the signal has to be deconvoluted) allowed to clearly identify "cathodic" and anodic sites on Al- alloys [1]. Careful potential calibration and surface conditioning with solution exposure generating the formation of an electrochemical double layer allow obtaining local thermodynamic information closely linked to "practical electrochemical potential series" measured in bulk solution conditions. This contribution will start by revisiting some "historical" examples of AFM-SKPFM characterization (a tribute to Jerry Frankel's activities) of aluminum and magnesium alloys [1,2]. These materials surfaces will further be used to show how reaction kinetic information on corrosion processes can be obtained with similar lateral resolution by means of the newly developed Scanning Electrochemical Nanocapillary (SEN) technique. After introducing the SEN technique and methodology, the presentation will focus on showing how the combination of these two approaches allows refining the local corrosion mechanism assessment of heterogeneous materials. The SEN technique is very versatile and allows various types of electrochemical measurements to be performed with constant tracking of the topography. The technique is based on a nanocapillary glass tip (< 100 nm) excited laterally by a piezoelectric element. A control of the capillary vibration damping when approaching the surface and a feedback loop (like the tapping mode in AFM) allows a very precise control of the approach and electrolyte contact on the surface. The glass capillary filled with the electrolyte of interest integrates a reference and Pt counter electrodes to perform electrochemical measurements exposing only the area of interest to aggressive electrolytes. Using its "hopping" mode (a scan with electrochemical characterization of successive individual nanoscale areas), corrosion initiation susceptibility can be addressed. This will be illustrated through the surface reactivity study of model Al-Cu-Mg microscale intermetallics and Mg-based alloys, using SEN OCP linescans. In addition information about extend of the attack can be subsequently retrieved from SEM observations. Using the precise positioning ability of the SEN setup with X, Y and Z direction piezos, potentiodynamic polarization measurements can furthermore be performed on selected area of interest. The example of an Mg-Fe composite material will be used to discuss its local electrochemical behavior.After the presentation of the SEN characterization results, additional aspects of the measured potential by AFM-SKPFM will also be discussed as adsorbed species, especially strong dipolar molecules, can significantly contribute to the measured signal [3]. Modification of the AFM-SKPFM setup towards atmospheric corrosion investigation will finally be presented. This environmental AFM/SKPFM bridges the gap between the full electrochemical local characterizations that can be offered by the SEN technique and an "electrochemical reaction" diagnostic obtained by SKPFM in thin water layer. The example of a very reactive WC-Co composite will be presented to demonstrate the reactivity issue, galvanic coupling controlling local dissolution processes [4].AcknowledgementsGerald Frankel for the great time I spent at Ohio State University in the Fontana Corrosion Center developing the AFM-based SKPFM methodology. Empa for internal project financial support of the SEN instrument.

Study of Ultimate Tensile Strength and Wear Rate of Squeeze Cast Al-Si-Cu Alloy with DOM and TOPSIS Approaches

Aluminium alloys are widely used to produce aerospace and agricultural sector components. Squeeze casting (SQC) is a liquid forging process to enrich the mechanical characteristics of light metal alloy castings. Al-Si-Cu castings were fabricated through SQC process adopting Response Surface Methodology (RSM) following Box-Behnken experimental design. Fifteen castings were fabricated by varying input factors such as squeeze pressure, pouring temperature and dwell time. Optimal process parameter settings were predicted for the responses Ultimate Tensile Strength (UTS) and Wear rate by Desirability Optimization Methodology (DOM) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The details of experiments and analysis are presented. The examination of microstructure and worn-out surface of squeeze castings indicated that the refi ned grain structure due to squeeze pressure application improved UTS and Wear resistance. Confi rmatory tests were conducted for settings suggested by DOM and TOPSIS. The setting suggested by DOM resulted in greater improvement. The value of UTS and wear rate predicted with DOM were verifi ed through confi rmatory tests and the measured values are in agreement with predicted values. An optimal improvement of 99.3% and 53.75% were achieved on ultimate tensile strength and wear resistance respectively in comparison with gravity die-cast components.

Efficient and temperature-independent terahertz emission from CoFeB/NiCu heterostructures

Spintronic terahertz (THz) emission has been investigated in ferromagnetic (FM) metal/nonmagnetic (NM) metal, FM/semiconductor, and FM/topological insulator systems. However, THz emission in the heterojunction of FM and $3d$ transition light metal is rarely reported. Large spin Hall angles have been observed in a light metal alloy of the $3d$ transition metal NiCu, allowing for the emission of high-performance THz waves without the use of heavy metal. Here, we present a comprehensive study of THz emission from a CoFeB/NiCu heterostructure, with peak intensity of emitted THz pulses up to half that of CoFeB/Pt. The THz radiation from CoFeB/NiCu is shown to be generated by the spin-to-charge conversion in NiCu via the inverse spin Hall effect. The evolution of the THz signal of $\mathrm{CoFeB}/{\mathrm{Ni}}_{70}{\mathrm{Cu}}_{30}$ across ${\mathrm{Ni}}_{70}{\mathrm{Cu}}_{30}$ Curie temperature is also explored, and it is discovered that the THz emission signal in this sample is temperature independent and unaffected by the magnetic state of ${\mathrm{Ni}}_{70}{\mathrm{Cu}}_{30}$. Our findings highlight the great potential of light metal alloys containing $3d$ transition elements as spintronic THz emitters. Moreover, it has been demonstrated that THz emission spectroscopy is a helpful tool for investigating inverse spin Hall effect or anomalous Hall effect in ferromagnets.

Characterization of an Al-Cu-Mg-Zn multi principal element alloy by experimental and computational screening methods

We present a combined experimental and computational investigation of phase stability and mechanical properties in the Al-Cu-Mg-Zn quaternary system. Samples containing different relative compositions were prepared using magnetron sputtering and investigated by electron microscopic and X-ray based methods. To classify the technical relevance of the samples, the indentation hardness was measured. The phase stability was studied computationally using a cluster expansion approach based on density functional theory (DFT) methods in a comprehensive screening of the structural and stoichiometric configuration space. Upon decreasing Cu concentration, a transition from an FCC to a mixed FCC/BCC crystal system and significant changes in the mechanical properties depending on Valence Electron Concentration (VEC) and atomic size differences (δr) was observed experimentally. The corresponding crystallographic phases were assigned by XRD and the experimentally observed phase transition was confirmed by the computational screening of formation energies. Since to date, quaternary complex light metal alloy systems cannot be reliably predicted, this is an important step towards a priori modelling of this class of materials.

Friction Stir Welding of Thick Plates of 4Y3Gd Mg Alloy: An Investigation of Microstructure and Mechanical Properties.

Applications of non-ferrous light metal alloys are especially popular in the field of aerospace. Hence it is important to investigate their properties in joining processes such as welding. Solid state joining process such as friction stir welding (FSW) is quite efficient for joining non-ferrous alloys, but with thick plates, challenges increase. In this study, Mg alloy plates of thickness 11.5 mm were successfully welded via single-pass FSW. Due to the dynamic recrystallization, grain size in the stir zone was reduced to 16 µm which is ≈15 times smaller than the parent material. The optimized rotational speed and traverse speed for optimum weld integrity were found to be 710 rpm and 100 mm/min, respectively. A sound weld with 98.96% joint efficiency, having an Ultimate Tensile Strength (UTS) of 161.8 MPa and elongation of 27.83%, was accomplished. Microhardness of the nugget was increased by 14.3%.

Fabrication of CNT-Reinforced 6061 Aluminium Alloy Surface Composites by Friction Stir Processing

The priority for transportation industries is to improve fuel efficiency by employing light composites. Carbon nanotubes (CNTs) have been incorporated into polymers and ceramics as reinforcing fibers, with recent studies focusing on fabrication of metal matrix composites. Integration of CNTs with light metal alloys, such as Al-6061, is expected to make strong but light composites. In this study, friction stir processing (FSP) is used to manufacture CNT-reinforced aluminium alloy surface composites, and their ultimate tensile strength, yield strength, and ductility are investigated. Their strength reached up to 178 MPa for the samples manufactured with 1500 rpm speed and 80 mm/min feed rate. Scanning electron microscopy was used to investigate their fracture surface morphology, and ductile failure was revealed. The highest temperature rise of 270°C was recorded during FSP, which is just above the plasticization temperature but far below the melting temperature of Al-6061 for the phase to change.

Evaluation of Prestrain Annealing Impact on Nanomaterial Sensitization

Light metal alloys are extensively used in automotive, aerospace, aircraft, and military sectors since their lightweight leads to reduced energy consumption, increased fuel efficiency, and better environmental protection. In the present situation, nanomaterials are the potential candidate for weight saving in the structural application and can meet stringent government norms. Nanomaterial was heat-treated in the furnace to about a certain temperature and time and then normalized for strengthening. The heat-treated nanomaterial undergoes different forging processes, namely, hot forging and cold forging, using a certain capacity’s hydraulic press. Hence, in this work, an extensive study on the influence of the prestrain annealing, the corrosion rate on differently treated samples, and the effect of sensitization heat treatment on the nanomaterial was done.