Al Alloy Matrix Research Articles

Fabrication of high-performance Al-Cu-Mg matrix composites via laser powder bed fusion: Incorporating advanced materials and lattice structures

The Laser Powder Bed Fusion (LPBF) process for Al-Cu-Mg alloys, such as the 2024 alloy, is fraught with challenges, primarily due to thermal cracking and the complexity of fabricating lattice structures. This study presents a systematic exploration of the LPBF process capabilities for 2024 Al alloy, a representative Al-Cu-Mg alloy, by incorporating cost-effective micron-scale TiCN ceramic reinforcement particles. The introduction of TiCN significantly modifies the consolidation mechanisms of the 2024 Al alloy matrix during LPBF process, effectively eliminating thermal cracking, refining the matrix grain size, and therefore significantly enhancing the mechanical behavior of Al-Cu-Mg alloys. Nonetheless, this study incorporates advanced lattice structure design to the LPBF processing of 2024-5 vol% TiCN composite material. When compared to Cubic and Diamond structures, Schwarz one demonstrates superior compressive strength, which suggests that higher surface area design of the lattice structures may contribute to the improved mechanical properties. This research offers a novel and economical approach to the development of high-performance Al-Cu-Mg materials tailored for LPBF, laying a groundwork for applications in aerospace, automotive manufacturing, and other sectors.

Effect of Cu alloying on the damping and compression properties of graphene nanoplatelets reinforced Al-30Zn-xCu alloy matrix composites

For a long time, metal matrix composites (MMCs) have always faced a trade-off between damping and mechanical properties, and this is especially true for high-Zn Al alloy matrix composites. In this study, graphene nanoplatelets (GNPs) reinforced Al-30Zn-xCu-0.5GNPs laminated composites with excellent damping-mechanical property balance were fabricated by flake powder metallurgy and Cu alloying. The addition of Cu element greatly refines the intragranular and intergranular precipitated η-Zn phases, which not only increases the Al-Zn interfacial area but also weakens the tendency of cracking at the grain boundaries. The increased Al-Zn interfacial area is conducive to the improvement of the damping performance of the composites through the interfacial damping mechanism, but the excessive generation of θ-CuAl2 induced by too high Cu additions will harden the matrix, resulting in a simultaneous decrease in the damping performance and plasticity.

Effects of Diamond Content on the Morphology and Compressive Properties of Porous Aluminum Composites.

Porous aluminum (Al) is popular due to its lightweight properties and impact energy absorption. However, it often has a lower mechanical strength than solid Al. To improve the performance, diamond reinforcement was introduced into the matrix. Further, addressing the challenge of interfacial bonding between Al and diamond, coated diamond with varying contents of 5, 10, 15, and 20 wt % was added to the porous Al alloy matrix via the powder metallurgy technique. The porosities were formed by using poly(methyl methacrylate) (30 wt %) as a space holder. The densities of the resultant porous composites ranged from 2.20 to 2.37 g/cm3 and porosities ranged from 33 to 38% for 5-20 wt % diamond contents. Furthermore, the yield strength and plateau stress increased from 21.47 to 29.46 MPa and 14 to 20 MPa, respectively, up to 10 wt % diamond content but declined upon further addition. Similarly, the energy absorption capacity increased from 2.15 to 2.95 MJ/m3 up to 10 wt % diamond content and thereafter decreased. Thus, the addition of coated diamond and alloying elements in Al strengthened the porous Al composites, making it suitable for applications requiring good compressive strength and energy absorption capacity.

Synergistic effect of Al2O3-decorated reduced graphene oxide on microstructure and mechanical properties of 6061 aluminium alloy

In this study, Al6061 alloy matrix composites reinforced Al2O3-decorated reduced graphene oxide (Al2O3/RGO) with 0.1, 0.3 and 0.5 weight present (wt%) were successfully fabricated using high energy ball milling and hot extrusion techniques. The microstructures of these Al2O3/RGO/Al6061 aluminum matrix composites (Al MMCs) were characterized. The results showed that Al2O3/RGO were uniformly distributed within the Al6061 matrix and tightly bonded to the matrix. Al2O3 encapsulation on RGO surface would prevent the formation of Al4C3 brittle phase in matrix, ensuring that there was no reaction between the reinforcement and the matrix Al6061. Tensile strength and Vickers hardness tests demonstrated that the mechanical properties of Al MMCs significantly increased with addition of Al2O3/RGOs. Remarkably, Al MMCs with 0.1 wt% reinforcement showed tensile yield and tensile strengths of 270 MPa and 286 MPa, respectively, which were 49% and 43% higher than those of pure Al6061 prepared using the same process. Furthermore, the 0.1 wt% Al2O3/RGO composite also showed the best plastic deformation capability in considering of the strength.

Effect of B4C and graphene on the microstructural and mechanical properties of Al6061 matrix composites

Materials that are lightweight with superior strength and improved structural properties have consistently been highly sought after in the aircraft and automobile industries for their superior performance. This study investigates the effect of graphene and boron carbide (B4C) additions on the microstructural & mechanical properties of Al6061 MMCs in fabricated and T6 heat-treated conditions. The powder metallurgy technique is used to fabricate the Al6061 hybrid composites reinforced with different volume fractions. i.e 0.5,1 wt% of graphene and 3,6 wt% of B4C. XRD, Optical microscope, FE-SEM with EDAX mapping, Hardness, and Compression tests were employed to evaluate and characterize the Al6061/Gr/B4C hybrid composites. After the T6 ageing treatment, both hardness and compressive strength were increased to 61.08% and 68.51% compared to base Al6061 matrix alloy. The sample Al6061/0.5% Gr/6%B4C-T6 exhibits the highest hardness value of 91HV and sample Al6061/1%Gr/6%B4C-T6 gives the value of higher compressive strength of 298 MPa. The higher tensile strength was observed in the sample Al6061/0.5%Gr/6%B4C-T6 which is 209.53 MPa with 8.907% elongation. The T6 heat treatment has a significant role in the strength improvement. Whereas increment in graphene has no impact on the tensile strength. The tensile strength of Al6061/0.5%Gr/6%B4C-T6 was improved by 43.56% compared to the base Al6061 alloy.

Unveiling the strengthening and toughening effects of copper-coated carbon nanotubes for the AlLiCu alloy matrix composite

Carbon nanotubes (CNTs) reinforced Al–Li–Cu alloy matrix composite is a promising candidate for the lightweight structural materials demanded in advanced industrial areas such as aerospace. However, how to fully exploit the combined strengthening effects of CNTs and precipitates of the Al–Li–Cu matrix is still an open issue. In the present study, the Cu coating was firstly precoated on CNTs before fabricating CNTs reinforced Al–Li–Cu alloy matrix composite. Benefiting from the Cu coating, the improved CNTs dispersion and Al-CNTs interfacial bonding was achieved, and the precipitation of Al2Cu, Al2CuLi, and Al3Li was enhanced in the AlLiCu alloy matrix, resulting in the enhanced strength-ductility synergy for Cu-coated CNTs reinforced AlLiCu alloy matrix composite. Moreover, strengthening and toughening mechanisms analyzation reveals that the Orowan strengthening of CNTs and precipitates, as well as load transfer strengthening of CNTs contribute mostly to the improved strength, while the increased ductility dominantly derives from the improved CNTs dispersion and Al-CNTs interfacial bonding, and the formation of low-density dislocation nanoregion (LDDN) in the interface area. This study not only opens up a new way for developing the AlLiCu alloy matrix composite reinforced by Cu-coated CNTs but also guides the microstructure regulation of other Al alloy matrix composites.

Enhanced strength-ductility synergy in a gradient pseudo-precipitates heterostructured Al-2.5%Mg alloy: Design, fabrication, and deformation mechanism

Heterostructures of alloyed composites, comprising heterogeneous domains with dramatically different constitutive properties, hold remarkable potential to expand the realm of material design systems and resolve the trade-off between strength and ductility. This study introduces an innovative materials design method for synthesizing gradient pseudo-precipitates heterostructure (GPHS) in non-heat-treatable Al-2.5%Mg alloys. Utilizing cost-effective mild steel as both the diffusion source and protective layer, this heterostructure is achieved through pin-less friction stir-assisted cyclic localized deformation process. Exogenous Fe atoms diffuse across the interface by friction stir-induced heat conduction, forming Fe-Al second-phase particles in the Al alloy matrix. A rapid inter-diffusion mechanism is activated in conjunction with dense dislocation walls, grain boundaries, and sub-structures, resulting in the formation of pseudo-precipitates. These pseudo-precipitates are ultimately dispersed in a gradient distribution throughout the entire thickness of the Al alloy matrix induced by localized incremental deformation. The GPHSed Al-2.5%Mg alloy exhibits an enhanced synergy of strength and ductility, with a uniform elongation increase from 11 % to 21.2 %, while maintaining the strength. Multiple strengthening and hardening mechanisms, such as solid solution strengthening, dislocation hardening, and second phase strengthening, work synergistically to promote mechanical performance. Notably, the hetero-deformation between hard pseudo-precipitates and soft Al alloy matrix induces additional strain hardening, leading to high ductility. This work provides a fresh perspective on the design and fabrication of high-performance alloys with advanced heterostructures, especially for non-heat-treatable alloys.

Evaluating the Effect of Different Percentage Addition of SiC on Mechanical and Wear Properties of Al6061 Composite

AbstractAluminum 6061 alloy using silicon carbide (SiC) particles as a reinforcement is a promising metal matrix composite (MMC) that has gained significant attention in the automotive and aerospace industries. Till now the effect of the addition of SiC particles in Al6061 composite is not studied in depth and also very few studies are reported the on‐wear properties of Al6061‐SiC composite. So, to further enhance the properties of Al6061 alloy and to study in depth this work is carried out. In this study, MMCs are prepared using the stir casting route with varying weight fractions (5–10 wt%) of SiC particles. The properties of composites including tensile strength, compression strength, and wear are evaluated experimentally. The results demonstrated that the incorporation of SiC particles into the Al alloy matrix leads to a notable improvement in mechanical and wear parameters. The tensile and compression strength of the Al composites increases with an increase in the weight percentage addition of SiC particles (from 5% to 7.5%). At 7.5 wt% addition of SiC, it is found that the particles are uniformly distributed throughout the Al6061 alloy matrix. And also shows higher mechanical and wear properties as compared to 5% and 10% addition.

Optimum selection of nano-Al2O3, nano-SiO2, and nano-ZrO2 particulate fillers on physical, mechanical, and wear assessment of Al6061 nanocomposite using preference selection index

The present study investigated the role of three important nano-sized fillers such as nano-SiO2, nano-ZrO2, and nano-Al2O3 on mechanical and wear assessment of Al6061 alloy matrix composite and suggested the optimum compositions for the best performance for Al6067 alloy matrix composites. Preference selection index as optimization tool was used and attributes taken for optimizations were void content, hardness, tensile strength, flexural strength, fracture toughness, impact strength, specific wear rate at normal load of 25 and 55 N load, sliding velocities of 0.5 and 2 m/s, sliding distance of 500 and 2000 m, respectively. In general, all three nanofillers enhanced the mechanical and wear properties of Al6061 alloy matrix composite. In the steady state wear study, on increasing normal load from 25 to 55 N, the specific wear rate of Al6061, Al6061-3Al2O3, Al6061-3SiO2, and Al6061-3ZrO2 was increased by 58.7%, 33.2%, 15.4%, and 26.14%, respectively. On increasing sliding speed from 0.5 to 2 m/sec, the specific wear rate of Al6061, Al6061-3Al2O3, Al6061-3SiO2, and Al6061-3ZrO2 was increased by 27%, 13%, 6%, and 12%, respectively. On increasing sliding distance from 500 to 2000 m, the specific wear rate of Al6061, Al6061-3Al2O3, Al6061-3SiO2, and Al6061-3ZrO2 was increased by 41%, 36%, 9%, and 21%, respectively. Al6061-3SiO2 indicated the best composition in terms of mechanical and wear performance followed by Al6061-3Al2O3 and Al6061-3ZrO2. Hence, nano-SiO2 can be suggested as the best filler to enhance the mechanical and wear performance of Al6061-based nanocomposite. Therefore, nano-SiO2 reinforced Al6061 composite is indicated as the best suitable composite material for a large number of components in structural, automobile, marine, and aerospace industries.

Refinement of the Manufacturing Route and Evaluation of the Reinforcement Effect of MAX Phases in Al Alloy Matrix Composite Materials

Microwave Assisted Self-propagating High-temperature Synthesis (MASHS) was used to prepare open-porous MAX phase preforms in Ti-Al-C and Ti-Si-C systems, which were further used as reinforcements for Al-Si matrix composite materials. The pretreatment of substrates was investigated to obtain open-porous cellular structures. Squeeze casting infiltration was chosen to be implemented as a method of composites manufacturing. Process parameters were adjusted in order to avoid oxidation during infiltration and to ensure the proper filling. Obtained materials were reproducible, well saturated and dense, without significant residual porosity or undesired interactions between the constituents. Based on this and the previous work of the authors, the reinforcement effect was characterized and compared for both systems. For the Al-Si+Ti-Al-C composite, an approx. 4-fold increase in hardness and instrumental Young's modulus was observed in relation to the matrix material. Compared to the matrix, Al-Si+Ti-Si-C composite improved more than 5-fold in hardness and almost 6-fold in Young's modulus. Wear resistance (established for different loads: 0.1, 0.2 and 0.5 MPa) for Al-Si+Ti-Al-C was two times higher than for the sole matrix, while for Al-Si+Ti-Si-C the improvement was up to 32%. Both composite materials exhibited approximately two times lower thermal expansion coefficients than the matrix, resulting in enhanced dimensional stability.

Characterization of wear rate of Al-12 wt%Si alloy based MMC reinforced with ZrO2 particulates

The primary objective of this study is to fabricate an Al-12 wt% Si Alloy/ZrO2 composite using the Stir Casting technique, with a specific focus on assessing its performance, particularly in terms of wear characteristics. This research presents a unique approach by utilizing Al-12 wt% Si Alloy as the matrix material, aiming to develop tailored Al Alloy matrix composites suitable for applications requiring enhanced tribological properties. The composites are systematically manufactured with varying percentages of micro-sized ZrO2 reinforcements, specifically 0.5, 1, and 3 wt%. The incorporation of ZrO2 results in significant improvements in wear resistance, a critical attribute for Al-12 wt% Si Alloy-based composites. These composites find extensive utility across industries such as marine, aerospace, automotive, and the power sector, where they are indispensable for producing vital components like electrical sliding contacts, gears, bearings, bushes, pistons, piston rings, and clutches. Despite the availability of various promising reinforcement materials, researchers persistently explore novel combinations of matrices and reinforcements to tailor properties and enhance cost-effectiveness. ZrO2 has emerged as a notable reinforcement material in metal matrix composites, as evidenced by numerous research endeavours. The composites fabricated with ceramic reinforcement’s exhibit enhanced tribological characteristics. The study observes that the wear rate decreases up to 3 wt% of reinforcements, beyond which it increases due to reinforcement agglomeration. The optimal wear-resistant combination is found at 3 wt% of ZrO2, attributed to robust micro-coring and interstitial metal-oxygen bonding facilitated by the Si content in the Al-12%Si matrix. The results are further optimized using Response Surface Methodology (RSM) techniques and validated using the ANOVA table to elucidate the behaviour of the composites under different operational conditions. The hardness results further ascertain the decrease in the wear rate due to the inclusion of ZrO2 reinforcements owing to micro coring and strengthening.

Experimental emulation of 10B(n, α)7Li reaction-induced microstructural evolution of Al-B4C neutron absorber used in the dry storage of spent nuclear fuel

Al-B4C neutron absorber in spent fuel dry storage could suffer significant radiation damage at elevated temperature (∼150–300 °C) mainly via 10B(n, α)7Li reactions. Several recent studies reported significant bubble formation in the absorber, however only from wet storage environment at near ambient temperature (< ∼90 °C). In this study, we irradiated a commercially widely used Al-B4C absorber of interest utilizing 120-keV helium ion-beam accelerator with twelve different conditions; three different doses (0.01, 0.1, and 1 dpa) combined with four different temperatures (room temperature, 150, 270, and 400 °C). This was to investigate the irradiation-induced microstructural evolution of the absorber in dry storage environment in expedited manner instead of time-consuming neutron irradiation test. The effects of irradiation dose and temperature on helium bubble nucleation and growth were investigated by image analysis on BF-TEM images, which showed a typical tendency of increasing bubble size with increasing temperature at the expense of decreasing bubble number density. Helium bubble morphology at grain boundaries was quite similar with the ones reported from the previous studies on the surveillance coupons used in the wet environment, elliptic helium bubbles around B4C particles. Notable difference was the prominent formation of numerous helium bubbles even from the lowest dose (0.01 dpa) at slightly elevated temperature (150 °C), perhaps due to higher irradiation temperature than that of spent fuel pool. This study may experimentally confirm that significant bubble formation and growth in the absorber could be the case from the early stage of the dry storage, even without the participation of hydrogen produced from the absorber corrosion. Particularly in the case of non-clad Al-B4C absorber, possible B4C particle detachment may need to be concerned since the bubble coalescence was concentrated at the interface between Al alloy matrix and B4C particle which would be microcracked under neutron irradiation.

Simulation of Radiation Damage and He Accumulation Induced by 10B(n, α)7Li Reactions in Al-B4C Neutron Absorbers Used in Spent Fuel Pools

Faster than expected surface corrosion and a considerable decrease in the 10B areal density of a non-clad Al-B4C neutron absorber were recently reported from surveillance coupons used in a spent fuel pool for about 8 years, which is only approximately one-fifth of the guaranteed service life of the absorber. Such premature degradation was largely attributed to irradiation-assisted corrosion since numerous gas bubbles filled with He and H were discovered in the Al alloy matrix near B4C particles, and naturally 10B(n, α)7Li reactions were designated as the underlying mechanism for the porosification that may have expedited the absorber corrosion. In this study, the levels of radiation damage and He concentration in the micrographs published in recent experimental studies were estimated to design ion beam irradiation experiments having appropriate parameters to emulate the status of neutron-irradiated non-clad Al-B4C absorbers. TRITON, CSAS6, and SDTrimSP were coupled with modifications for the calculation of dpa and He concentration in irradiated neutron absorbers. The simulations yielded 3.74–6.71 dpa and 0.71–1.64 at% of He after 99 months of use and 3.82–8.39 dpa and 0.73–2.08 at% of He after 40 years of use. The simulations also demonstrated that the radiation damage and He concentration have a weak correlation with the particle diameter. In terms of radiation damage, these results are in good agreement with the reported experimental data, indicating that they can be referred to in the experimental design. The calculated He concentrations, however, may warrant modification to include leakage of implanted He atoms through irradiation-induced microcracks in the B4C particles. Because of the high diffusivity of He, full leakage of He from B4C particles to their boundaries with the Al alloy matrix was assumed for further estimations, which revealed that He concentration could be significantly elevated in the Al matrix near B4C particles.

Evaluation of Mechanical Properties of Al6061 Composite by Stir Casting Method

Aluminium alloy-based metallic matrix composites (MMC) have recently gained popularity in various aerospace and automotive applications. Aluminium has been utilized as a matrix material due to its high mechanical qualities, superior formability, and diverse industrial applications. The Al6061 alloy system becomes harder, stronger in tension, and more wear-resistant when TiB₂-SiC-Rh is added as reinforcement. Al6061–TiB₂-SiC-Rh composites were created in this study using a liquid metallurgical method, with TiB₂-SiC-Rh added in percentages ranging from 2% to 8% by weight in increments of 2%. The cast matrix alloy and its composites were treated with solutionizing at 500°C for 1 hour before being quenched in different media like air, water, and oil. After quenching, the samples were aged both artificially and naturally. Microstructural analysis was conducted to understand the relationship between structure and mechanical properties. Mechanical characteristics, including microhardness and abrasive wear experiments, were performed on matrix Al6061 and Al6061-TiB₂-SiC-Rh composites before and after heat treatment. Under the same heat treatment conditions, the Al6061-TiB₂-SiC-Rh composites exhibited improved microhardness, tensile strength, and reduced wear compared with the Al matrix alloy.

Mechanical, tribological, and morphological properties of SiC and Gr reinforced Al-0.7Fe-0.6Si-0.375Cr-0.25Zn based stir-casted hybrid metal matrix composites for automotive applications: Fabrication and characterizations

The main goal of this research is to meet the demanding need for developing lightweight materials with improved properties that are appropriate for several engineering applications. The investigators proceeded to considerable efforts to assess the mechanical, micro-structural, and tribological characteristics of Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/10 wt%SiCP/3 wt%GrP-MMC, Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/15 wt%SiCP/5 wt%GrP-MMC, and Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/20 wt%SiCP/8 wt%GrP-MMC based hybrid metal-matrix nano-composites (HMMC's). These hybrid aluminum matrix nano-composites were fabricated using the liquid processing stir casting method for automobile, aviation, defense, and chemical handling sectors owing to their superior strength, and higher thermal conductive properties. The machinability of Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/(SiCp + Grp) - MMC has received limited attention to date. Owing to its exceptional characteristics, this hybrid composite could take the role of cast iron or aluminum composites in a wide-variety multitude of engineering applications. The Mechanical properties of fabricated Hybrid-MMCs have been examined along with tribological properties & other factors, affecting the tensile strength of cast composites in this study. Additionally, the characterization has been performed through X-ray Diffraction (XRD), Energy Dispersive Spectrum (EDS), Scanning Electron Microscope (SEM), and Optical Microscopy. The fabricated samples of hybrid metal matrix nano-composites of Al-0.7Fe-0.6Si-0.375Cr-0.25Zn matrix have been tested for microstructure analysis, micro hardness test, density, tensile strength, and grain size. Microstructure study clears the claim of uniform distribution of SiC & Graphite particles in Al matrix alloy. An average tensile strength has been recorded as 258 MPa and a percent-elongation of 4.6 during the tensile test. Tensile-fractography findings have portrayed the intrinsic fractured-rupture microstructure of tensile-tested samples that seemed to have particle deformation breakage and pull-outs. The density of Al/(SiCp + Grp)-MMCs have been found to be 2.76 g/cm3 whereas the average hardness has been recorded at 120HV. An increase in graphite content in Al/SiC-MMC's provides a significant improvement in friction coefficient as well as a reduction in wear rate. Findings have observed that the wear rate is increased with increasing the sliding speed, however, it is almost constant between 300 and 600 rpm, and beyond this wear rate increases drastically. Likewise, the coefficient of friction also shows a considerable increase with the increase in sliding speed. As the composition of graphite in the material increases, a considerable decrease in the wear has been noted down because of the presence of tribo-layer formed between mating surfaces. A high value of applied load and high rotating speed imposed high deformation of the surface and increase in frictional force, as a result, an increase in wear rate. Wear rate increases with the increment in load during the wear test, while friction coefficient decreases. Hence, the development of HMMCs with better mechanical, microstructural, and tribological properties that can be utilized as cast iron or aluminum composites in a diverse spectra multitude of engineering applications involving the study's scientific insights and technological developments. Manufacturers in the myriads of industries, including aerospace, ground-transportation, thermal management, industrial, recreational, and infrastructure, could profit inventors/producers from the findings of the current study.

Fatigue crack growth rate and propagation mechanisms of SiC particle reinforced Al alloy matrix composites

PurposeThis study aims to investigate the fatigue crack propagation behavior of SiC particle-reinforced 2124 Al alloy composites under constant amplitude axial loading at a stress ratio of R = 0.1. For this purpose, it is performed experiments and comparatively analyze the results by producing 5, 10, 15 Vol.% SiCp-reinforced composites and unreinforced 2124 Al alloy billets with powder metallurgy (PM) production technique.Design/methodology/approachWith the PM production technique, SiCp-reinforced composite and unreinforced 2124 Al alloy billets were produced at 5%, 10%, 15% volume ratios. After the produced billets were extruded and 5 mm thick plates were formed, tensile and fatigue crack propagation compact tensile (CT) samples were prepared. Optical microscope examinations were carried out to determine the microstructural properties of billet and samples. To determine the SiC particle–matrix interactions due to the composite microstructure, unlike the Al alloy, which affects the crack initiation life and crack propagation rate, detailed scanning electron microscopy (SEM) studies have been carried out.FindingsOptical microscope examinations for the determination of the microstructural properties of billet and samples showed that although SiC particles were rarely clustered in the Al alloy matrix, they were generally homogeneously dispersed. Fatigue crack propagation rates were determined experimentally. While the highest crack initiation resistance was achieved at 5% SiC volume ratio, the slowest crack propagation rate in the stable crack propagation region was found in the unreinforced 2124 Al alloy. At volume ratios greater than 5%, the number of crack initiation cycles decreases and the propagation rate increases.Originality/valueAs a requirement of damage tolerance design, the fatigue crack propagation rate and fatigue behavior of materials to be used in high-tech vehicles such as aircraft structural parts should be well characterized. Therefore, safer use of these materials in critical structural parts becomes widespread. In this study, besides measuring fatigue crack propagation rates, the mechanisms causing crack acceleration or deceleration were determined by applying detailed SEM examinations.

Correlation between pitting susceptibility and surface acidity, point of zero charge of passive film on aluminum: Influence of alloying elements

The pitting potential, intrinsic surface acidity, point of zero charge of passive film on Al are studied using first-principles calculations to establish their relationships. Influences of alloying elements Zn, Cr, Nb, Si, Mo and Sc on adsorption of NH3 and NaCl, pHpzc of Al2O3 and pitting susceptibility of Al are investigated. The efficiency for enhancing pitting resistance of Al is evaluated, yielding the ratios Si: Zn: Cr: Mo: Nb: Sc = 1.8: − 0.3: 1: 1.9: 1.4: 0.2. A model for the dependence of pitting potential on the concentration of alloying elements in Al alloy matrix is developed, based on effects of alloying elements on the surface charge of passive film. The effects of Sc on pitting potential and pHpzc of Al oxide are predicted based on the calculated results, which are supported by electrochemical measurement, XPS analysis and contact angle titration.

Wear surface characterization of hybrid Al alloy-based nanocomposites

Using liquid metallurgy route, an aluminumAl6061-1.2 wt% nanoSiC-0.5 wt% graphite hybrid nano-composites composite was fabricated. The dry sliding wear characteristics of thehybrid nano-compositeswere investigatedunder various sliding parameters using the pin-on-disc apparatus.The prepared hybrid nanocomposite were examined for wear surfaces by using the Field Emission Scanning Electron Microscope (FESEM)and 3Dprofilometer. Al/1.2SiC/Gr hybrid nano-composites performed better than the Al6061 matrix alloy in terms of wear resistance. The hybrid nano-composite wear surface roughness was 1.560 µm but the alloy matrix roughness was 6.20 µm at 0.5 m/s under 40 N. Comparing the Al/1.2SiC/Gr nanocomposites to the Al6061 matrix alloy, the surface smoothness was found to be the best.

Exploring the intricacies of machine learning-based optimization of electric discharge machining on squeeze cast TiB2/AA6061 composites: Insights from morphological, and microstructural aspects in the surface structure analysis of recast layer formation and worn-out analysis

Aluminium (Al) Alloy-6061/TiB2 was developed with Squeeze casting while varying composite quantities with titanium diboride (TiB2). The metallographic structure of the composite was investigated using EDS and scanning electron microscopy (SEM). The machining of developed composite is challenging with the conventional methods due to higher tool wear and surface roughness (Ra). This study analyses the output responses, and machinability of TiB2 of 15% volume reinforced AA6061 composites using Electrical Discharge Machining (EDM). The EDM operation variables such as current, pulse on time, and voltage gap were utilized to examine material removal rate (MRR), tool wear rate (TWR) and Ra employing Box–Behnken design of experiments. The MRR, TWR and Ra data acquired from various experiments were optimized considering single and multiple objectives by a hybrid approach. Machine learning (ML) was applied to predict responses using linear regression (LR), decision tree (DT) and random forest (RF). The samples' recast layer was examined using SEM, and the thickness of the recast layer was also documented. The Al6061 alloy's SEM micrographs reveal deep equiaxed dimples on its fracture surface, indicating a high level of plastic deformation before failure. TiB2 is evenly distributed as darker particles in the Al-matrix alloy with no directional-orientation. The Al6061-15 wt% TiB2 composites' fracture surfaces display deep dimples, ductile-fracture for Al6061 alloy due to higher plastic deformation, and cleavage facets in some areas. The aluminum alloy's wear pattern depicts long, extensive ploughing grooves with short cracks parallel to the sliding direction at the grooves' bottom. SEM micrographs in recast-layer formation have reported that molten metal ligaments break into droplets during flushing, exposing fresh surfaces. The aluminum alloy's groove width is larger compared to the composites. Thus, it can be observed that the wear tracks on the base Al6061 alloy are larger and deeper in comparison to the Al- 15 wt% TiB2 surface composites due to the presence of hard TiB2 particles. Also, the recast layer may be advantageous due to its wear-resistant properties. TiB2 has importance in an industry where components slide with each other it is used in disc brakes in automobiles. Compared to industry standards, single-objective optimization considerably enhanced the outcomes: MRR increased by 10.61%, TWR enriched by 25.91%, and Ra increased by 17.60%. According to an ANOVA, peak current contributed 87.88%, 98.18%, and 95.80% respectively to MRR, TWR, and Ra. It is requisite to investigate multi-objective optimization for EDM of Al6061-15 wt% TiB2 composites' owing to the diverse optimal factor combinations for responses. Ra was slightly increased by 1.14% due to simultaneous optimization utilizing hybrid techniques with Equal and Entropy weights, which diminished TWR by 11.74% and increased MRR by 11.66%. ML, particularly DT, improves machining performance by assisting productivity, durability, and cost-efficiency under changeable circumstances and raising forthcoming study possibilities.

The crystallographic orientation dependent anisotropic corrosion behavior of aluminum in 3.5 wt% NaCl solution

In this paper, a quantitative method to evaluate the degree of differences in corrosive behavior of different crystallographic-oriented planes of Al and Al alloys in 3.5 wt% NaCl solution is provided. The corrosion potential Ucorr, corrosion current density Icorr and electrochemical corrosion rate of (100), (110) and (111) ideal surfaces and corresponding surfaces with vacancy and chloride ion adsorption considerations in single-crystal aluminum were derived by first principles calculation. The results show that the corrosion potential and corrosive current density increases in the order of U(110)corr<U(100)corr<U(111)corr and I(111)corr<I(100)corr<I(110)corr, respectively, and the electrochemical corrosion rate of (111) surface is 0.01×10-3 mm/a, showing the superior corrosion resistance. Moreover, the effect of the addition of alloying elements on the corrosion behavior of M−alloying Al alloy matrix in comparison with pure Al was further investigated by first principles calculation, and elements of Li, Mg, Zn, Ag and Cd are selected to improve the corrosion resistance of Al alloy.