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Because of its improved formability, lower production costs, and mechanical properties, aluminum metal matrix composite is the highly intriguing engineering material. It can meet the needs of modern engineering applications used in the automotive, military, aerospace, and marine industries. Hybridization of reinforcement is adopted to develop tailor‐made properties of composites for specific application. In this study, Al‐B4C‐Gr hybrid composites were produced with varying graphene content (0.25, 0.50, 0.75, and 1 wt.%) and keeping boron carbide (10 wt.%) as constant, the effect of graphene proportion on the mechanical properties of produced composites was evaluated. It has been observed that increasing the Gr reinforcement particles in the synthesized composites improves the mechanical characteristics of the composites, such as raising the tensile strength to 215 Mpa and the hardness to 110 HV due to the presence and proper distribution of reinforcement in the matrix. When compared to the base alloy, the tensile strength and hardness of Al10B4C0.75Gr composites rose by 27.174% and 67.290%, respectively. The dry sliding wear behavior of Al‐10 wt.% B4C‐wt.%Gr hybrid composites confirms that graphene and B4C particles in the matrix increase the wear resistance of the produced MMCs. The each parameter such as sliding distance, sliding velocity and load has its influence toward the better wear resistance of the developed composites and were discussed. [ABSTRACT FROM AUTHOR]

Accurate prediction of cutting force is essential not only for estimating power and torque but also for precise chatter prediction, where even the derivative of the cutting force function is crucial. The traditional cutting force model does not consider the runout, and the enhanced models that consider it are often difficult to be established due to the need of physical runout measurements. This study proposes a newly developed split-wise model to predict the cutting forces in Al2024. This model includes the calculation of the cutting force considering individual teeth which leads to the determination of 6 force coefficients of different values per tooth. The experiments were conducted on milling Al2024 for two set of experiments ( V fz = 375–675 m/min, a e = 4–12 mm, a p = 0.5–1 mm, D =16 mm) and ( V fz = 220–440 m/min, a e = 0.5–1 mm, a p = 0.5–1 mm, D =2 mm). For the first set, the comparative error determined from the split-wise and classic models is 5.6% and 7.8%, respectively. For the second set, the error is 11% and 15.7%, respectively. Therefore, the split-wise cutting force model is capable of adapting the runout and consequently improving the prediction of the cutting force with both large and small tools operations. Additionally, the split-wise may find applications in advanced manufacturing technologies allowing industries to enhanced productivity and quality. [ABSTRACT FROM AUTHOR]

Abstract Because of its improved formability, lower production costs, and mechanical properties, aluminum metal matrix composite is the highly intriguing engineering material. It can meet the needs of modern engineering applications used in the automotive, military, aerospace, and marine industries. Hybridization of reinforcement is adopted to develop tailor‐made properties of composites for specific application. In this study, Al‐B4C‐Gr hybrid composites were produced with varying graphene content (0.25, 0.50, 0.75, and 1 wt.%) and keeping boron carbide (10 wt.%) as constant, the effect of graphene proportion on the mechanical properties of produced composites was evaluated. It has been observed that increasing the Gr reinforcement particles in the synthesized composites improves the mechanical characteristics of the composites, such as raising the tensile strength to 215 Mpa and the hardness to 110 HV due to the presence and proper distribution of reinforcement in the matrix. When compared to the base alloy, the tensile strength and hardness of Al10B4C0.75Gr composites rose by 27.174% and 67.290%, respectively. The dry sliding wear behavior of Al‐10 wt.% B4C‐wt.%Gr hybrid composites confirms that graphene and B4C particles in the matrix increase the wear resistance of the produced MMCs. The each parameter such as sliding distance, sliding velocity and load has its influence toward the better wear resistance of the developed composites and were discussed.

Günümüzde alüminyum alaşımları hafif olması, yüksek dayanım sunması ve ekonomik olmaları gibi sebeplerle havacılık, otomotiv ve savunma sanayiinde yoğun olarak kullanılmaktadır. Bu çalışmada Al2024-T3 malzemesinin işlenmesinde elektro erozyon yöntemi kullanılarak, talaş kaldırma miktarı (TKM), takım aşınma miktarı (TAM) ve ortalama yüzey pürüzlülüğü (Ra) olarak sıralanabilecek performans yanıtları üzerinden sonuçlar elde edilmiştir. Yapılan deneylerde boşalım akımı (Ip), vurum süresi (Ton) ve vurum aralığı (Toff) parametrelerinin performans yanıtları üzerindeki etkileri incelenmiştir. Yapılan varyans analizi (ANOVA) sonucunda deney sonuçları üzerinde etkin parametrelerin sırasıyla Ton, Ip ve Toff olduğu tespit edilmiştir. Çalışmanın devamında performans yanıtlarını eniyileyecek parametre değerlerinin tespiti amacıyla bir optimizasyon çalışmasına da yer verilmiştir.

Utilizing Laser Engineered Net Shaping (LENS), nanocomposites were generated by mechanically combining metal powders with various amounts of multi-walled carbon nanotubes (CNTs). To produce free-standing bulk structures and coatings, the LM6 (Al-12Si-0.6Fe-0.5Mn-0.3Mg-0.1Ni-0.1Zn) alloy was chosen owing to its exceptional corrosion resistance in typical atmospheric and marine environments. The LENS technique was employed to fabricate the coating-substrate interface for LM6 coated Al-2024 and MWCNT-LM6 coated Al-2024. The addition of MWCNTs to the Al-Si matrix enhanced the tribological properties of LM6. SEM images revealed abrasive wear as the primary wear mechanism. A pin-ondisc wear tester was utilized to study the friction and wear behavior of the composite under a load of 1 N and a sliding speed of 50 mms-1. The addition of MWCNTs resulted in a reduction of the friction coefficient because of the MWCNT's selflubricating characteristic and unique topological structure. Moreover, the volumetric wear rate dropped considerably, and thermal properties were significantly enhanced with the inclusion of MWCNTs. A 25% increase in thermal conductivity was seen after the addition of 8% vol MWCNTs to LM6 coated Al-2024. [ABSTRACT FROM AUTHOR]

Aluminium matrix composites are nowadays used globally as a substitute for other cast alloys because of their augmented properties. The present experiment deals with the fabrication and characterisation of tribological behaviour of titanium diboride reinforced aluminium matrix composite on a pin-on-disc tribotester under dry sliding condition. In this work, an attempt has been made to minimise the friction and wear characteristics of Al2024-TiB2 composite, by optimising the tribological parameters viz. applied load, sliding speed and sliding distance using grey-fuzzy approach. The tests are carried out based on Taguchi's L25 orthogonal array. Grey-fuzzy analysis is used for converting the multi-objective optimisation problem into a single-objective optimisation. Based on the grey-fuzzy analysis, the optimal combination of tribological parameters is L1S4D2 (10N load, 2.0 m/s sliding speed and 1000 m sliding distance). The optimal combination of parameters has also been validated with a confirmatory experiment. Analysis of variance (ANOVA) for grey fuzzy grade shows that sliding distance is the most significant parameter affecting tribological performance. SEM analysis of the worn surfaces revealed that, increase in sliding distance results in wear transition from mild to severe. The proposed grey-fuzzy method is found to be successful in solving multi-response tribological problems. [ABSTRACT FROM AUTHOR]

In this study, composites with Al2024 matrix and 10–20 µm size B4C + SiC, TiC + SiC, and B4C + TiC hybrid reinforcements were produced by the vacuum infiltration method. Reinforcements were added to the matrix in different weight ratios (1–10%). The dissolution and aging processes were applied to the hybrid parts. The effects of these processes on the hardness and microstructure were investigated by FESEM, EDS, XRD, and Vickers analyses. It has been observed that there is an increase in hardness with aging and an increase in hardness up to a 5% reinforcement ratio. In all samples, the highest hardness data was obtained after 6 h of the aging process. The highest hardness value among all hybrid composites was obtained in the 2.5%B4C + 2.5%SiC (total 5%) hybrid composite structure after 6 h of aging. The desired wettability and a homogeneous distribution of the hybrid reinforcements in the structure were achieved. [ABSTRACT FROM AUTHOR]

In this study, the applicability of hydroxyapatite (HA) coatings on Al-Cu-Mg alloys (Al2024) was investigated by electrochemical techniques. The structural characterizations of the coated layers were investigated by SEM, EDS, and XRD equipment. The surface adhesion resistance and electrochemical degradation behavior were tested by scratch and potentiodynamic scanning (PDS) tests, respectively. It was observed that the HA coating had a homogeneous structure on the Al2024 surfaces, but some local areas could not be adequately coated with HA from the cross-section images. Also, the coating surfaces were microporous morphology, which is specific to the HA coatings. From the scratch test results of the coating, it was predicted that the critical load resistance (Lc1), 12N, would be sufficient for biomedical applications. Electrochemical corrosion tests revealed that HA coating decreased the corrosion current density (Icorr) and corrosion rate of the Al2024 alloy (0.885 and 5.260 μA·cm-2 for HA-coated and uncoated Al2024 alloy, respectively). However, despite the low Icorr value obtained with HA coating, it was observed that both Icorr and passivation current density (Ipass) values (3.15 μA·cm-2 for HA coating, 0.03 to 0.08 μA·cm-2 for different types of titanium alloys) were insufficient when compared to commercial titanium alloys. [ABSTRACT FROM AUTHOR]

Al esaslı alaşımlar havacılık, otomotiv ve savunma sanayi gibi birçok sektörde kullanılmaktadır. Düşük yoğunlukları ve yüksek özgül mukavemet özellikleri, Al ve alaşımlarını mühendislik malzemeleri olarak kullanılabilir hale getirir. Al esaslı alaşımlar seramik partiküller ile takviye edildiğinde yüksek sertlik ve mukavemete sahip yeni nesil mühendislik malzemeleri olarak kullanılabilirler. Bu çalışmada Al2O3 partikülleri Al-Cu-Mg matrisine ağırlıkça %10, %20 ve %40 oranında mekanik alaşımlama (MA) yöntemiyle takviye edilmiş ve 560 oC, 500 MPa pres koşullarında sıcak pres (SP) yöntemiyle preslenmiştir. MA işleminden sonra partikül boyutu ölçümleri, partikül boyutlarının azaldığını ortaya çıkarmıştır. Al-Cu-Mg ve Al2O3 partiküllerinin MA işlemi öncesi partikül boyutu ölçüm sonuçları sırasıyla 212,434 μm ve 89,208 μm olarak ölçülmüştür. MA işlemi sonrası partikül boyutları %10, %20 ve %40 Al2O3 takviyeli numuneler için sırasıyla 14,224 μm, 13,747 μm ve 10,885 μm olarak ölçülmüştür. %10, %20 ve %40 Al2O3 içeriği ile üretilen numunelerin sertlik değerleri sırasıyla 146,867 HV (0,5), 165,290 HV (0,5) ve 206,843 HV (0,5) olarak ölçülmüştür.

Defects, such as pores and cracks, can be found in parts fabricated by powder-bed additive manufacturing techniques. The origin of certain defects, such as some voids, can be linked to initial powder quality, which makes it an important factor in the process. Powders used in additive manufacturing processes are produced by different methods such as gas atomization (GA), plasma atomization (PA), and plasma rotating electrode process (PREP); each gives different powder quality. In this study, two different Al2024 powders, produced by electrode induction GA and PREP techniques, were used to investigate the effect of powder characteristics on defect formation during electron beam melting process (EBM). Powders were first characterized by using Hall flowmeter funnel and scanning electron microscope (SEM); then, the EBM process was carried out, and finally, samples were examined by density measurement using Archimedes method, SEM analysis, and tensile test. PREP powder showed higher levels of sphericity and surface smoothness without attached satellites. Consequently, a higher apparent density and decreased flowing time were achieved in PREP powder. Moreover, gas-induced internal pores were observed in GA particles. The results also revealed the average relative density of 96.7% and 99.4% for the parts built by GA and PREP powders, respectively. SEM micrographs confirmed the results of density measurement of the fabricated parts and showed higher degrees of both spherical and irregular-shaped pores in samples built by GA powder. Additionally, they showed deprived mechanical properties due to the higher porosity contents which can form stress-concentrated areas. [ABSTRACT FROM AUTHOR]

Al2024 belongs to a typical Al-Cu-Mg series alloy. It has the advantages of high-strength, low-specific gravity, stress resistance, corrosion resistance, good heat resistance, and high fatigue resistance. It is widely used in aerospace, automobiles, ships, chemicals, and other fields. Aluminum alloys play a pivotal role in industry and manufacturing. Cemented carbide tools are often used in the processing of aluminum alloys, and diffusion wear is prone to occur during the processing. It is of great significance to study the diffusion phenomenon of WC tools in the process of cutting aluminum alloys for improving tool life and workpiece surface machining accuracy. In this paper, based on the molecular dynamics (MD) simulation method, the WC tool and the Al2024 model were established, the Morse potential parameters between the tool and the workpiece atoms were calculated, and the diffusion wear mechanism of the WC tool in the process of cutting Al2024 was studied. Through the displacement nephogram in the tool-worker X direction, it is found that the workpiece atoms have a tendency to diffuse to the tool. Using the mean square displacement (MSD) method, the diffusion velocities of Al, Cu, and Mg atoms in the workpiece were obtained. The results show that the activation energy of atomic vacancies at the grain boundary is smaller than that at the lattice, and the Al, Cu, and Mg atoms at the grain boundary of the workpiece are more likely to diffuse, and the diffusion rate of Mg atoms is the fastest. The total energy of single atoms in the cutting process was analyzed, and it was found that the energy required for Al, Cu, and Mg elements at the grain boundary of the workpiece to diffuse into the WC tool and the energy required for the Mg and Al elements at the workpiece lattice to diffuse into the WC tool were satisfied. [ABSTRACT FROM AUTHOR]

Aluminum copper alloys reinforced with naturally occurring or synthesized ceramic particulates are widely used for producing various automobile components and as structural supports by the aerospace industries. For improving their performance these composite materials have been further refined by the addition of nano materials. Nano sized graphene has played a significant role in this direction. In this present work an attempt has been made to refine Al2024/Albite composite in which the predominant primary reinforcement Albite of 5% by weight has been maintained constant and by addition of graphene as secondary reinforcement with varying content (0.25,0.50,0.75, 1, 1.25 and 1.5Wt%) the composite material was fabricated by adopting powder metallurgy. SEM images of the processed hybrid composites revealed the presence of primary reinforcement Albite and secondary reinforcement graphene reinforcements equitably distributed throughout the Al2024 alloy with very less presence of voids. An appreciable increase in compression strength and hardness has been observed with increase in addition to secondary reinforcement up to 1.25%Wt of graphene, but tends to decrease with further addition of graphene reinforcement. [ABSTRACT FROM AUTHOR]

The effect of friction stir welding (FSW) parameters on the microstructure, mechanical and electrical properties of 2024 aluminum alloy and copper joints was investigated. After obtaining the processing window, the optimum values of ultimate tensile strength≈ 142 MPa, elongation≈ 5 %, and electrical resistivity≈ 33 nΩm were obtained by FSW at a rotational speed (W) ≈ 948 rpm and a traverse speed (V) ≈ 85 mm/min. W/V ratio, which stands for the amount of heat input during FSW, had a considerable effect on the joints' properties. At W/V>(W/V)optimum, larger amounts of Al4Cu9 and Al2Cu brittle intermetallic compounds (IMCs), and at W/V

Aluminium matrix composites are scientifically engineered materials possessing higher potential in automotive, aerospace and defence applications. Therefore this study focuses on the fabrication of aluminium matrix composites reinforced with micro SiC particulates by stir casting process and investigating the effect of SiC content on mechanical properties as well as wear behaviour of the prepared composites. Different weight percentages (wt.%) of silicon carbide particulates (0, 3, 6 and 9%) were used. Stirring speed, time and other parameters were kept constant during the casting process. Microstructural characterization, tensile, hardness and wear tests were carried out of the casted samples. XRD analysis depicted the existence of SiC particulates in the prepared composites. Microstructural analysis confirms even distribution of reinforcement particulates. The experimental results revealed that, strength and hardness of the prepared composites improved with SiC addition. Wear resistance of SiC reinforced composites were also higher than that of the matrix alloy. The wear mechanism of matrix alloy was adhesive, whereas the wear mechanism changed to abrasive in case of SiC reinforced composites. The prepared composites exhibit augmented mechanical and tribological properties and can be used as a promising material in applications such as gears, drive shafts, brake drums and bearings. [ABSTRACT FROM AUTHOR]

Samples built by the additive manufacturing experience various thermal cycles during the process. This, as a result, defines the final microstructure of the samples. Herein, the dissolution of θ‐Al2Cu precipitate along the building direction during electron beam melting process is aimed at. Induced thermal cycles cause the layers to experience critical temperatures. The results show that the average fraction area of precipitates is decreased from 3.34% to 2.63% and finally to 2.02% by moving along the building direction from the top to the bottom. This is due to the fact that the first deposited layers are kept at temperatures more than 520 °C for longer times, which is higher than the critical temperature of Al2Cu dissolution. Because of the solubility limit of Cu in the matrix, precipitates are not fully dissolved. Comparing the ratio of the integration area of the strongest θ diffraction peak to that of the α matrix at different locations, the dissolution is also confirmed by X‐ray diffraction (XRD) results. The results of the tensile test also demonstrate a decline of about 29% in the mechanical performance by moving from the top to the bottom, which can be attributed to the precipitates' dissolution and grain coarsening. [ABSTRACT FROM AUTHOR]

Particulate reinforced aluminium matrix composites are one of the most attractive approaches for applications where high strength and hardness combinations are necessary. The aspiration of this study is to investigate the effect of titanium diboride addition on physical and mechanical properties of Al2024-TiB2 composites manufactured using stir casting route, by varying the weight percentages (wt.%) (0, 3, 6 and 9 percent) of titanium diboride particulates. During the casting process, stirring time and speed were kept constant and same for all the composites. Microstructural analysis demonstrates uniformity in TiB2 distribution and also strong matrix-reinforcement bonding which can be as a result of magnesium addition and preheating of titanium diboride particles before incorporating into the molten aluminium. With an increment in the wt.% of TiB2 particulates, hardness and tensile strength of the prepared composites improved, a significant improvement in hardness as well as tensile strength is encountered in Al2024-9% TiB2 composite, which is 44.94% and 35.49% higher than Al2024 matrix alloy, respectively. SEM analysis of the fractured surfaces revealed that the mode of fracture of unreinforced material is purely ductile but reinforced material fractured by nucleation of cracks and plastic deformation. [ABSTRACT FROM AUTHOR]

This paper encapsulates the comparative study of physical, mechanical as well as tribological properties of Al2024 alloy and its composites Al2024-SiC and Al2024-TiB2 prepared by stir casting technique. Microstructural characterization were conducted using SEM (scanning electron microscope) with EDS (energy-dispersive X-ray spectroscopy). Experimental investigation of density, porosity, microhardness, ultimate tensile strength and wear behaviour of Al2024 alloy and its composites were carried out. Microstructural characterization confirms uniform distribution of SiC and TiB2 particulates and excellent matrix-reinforcement interfacial bonding. Enhanced mechanical and tribological properties were observed for both the prepared composites compared to Al2024 alloy; this increment was higher for Al2024-TiB2 composite than Al2024-SiC composite. Al2024-TiB2 composite exhibits superior wear resistance with non-existence of plastic deformation and adhesion on the wear tracks. The size and shape of the debris also play an important role in determining the wear rates of Al2024 alloy and its composites. [ABSTRACT FROM AUTHOR]

The interface of fiber-polymer matrix has a critical role in controlling the mechanical features of polymer composites. Most of the studies focused on the application of reduced graphene oxide in enhancing the interfacial properties of the composite. In this study, we focused on utilising the Graphene nano-plates (GNPs) with average diameter of 5–10 µm. The GNPs were assessed by different techniques of XRD and AFM. The GNPs incorporated into the epoxy matrix, and then the high velocity impact response was evaluated. The result of GNPs incorporation into the epoxy matrix showed that the 0.3 wt.% GNPs incorporation into the glass fiber epoxy matrix and 0.9 wt.% GNPs incorporation into the glass-carbon fiber/epoxy were destructive on the absorption energy of the composite. The optimum concentration of the incorporated GNPs highly dependent upon the type of fiber in the matrix and the level of initial velocity in the impact test. Although the high concentration of GNPs (up to 0.9 wt.%) dispersed at the interface of the glass fiber/epoxy resin can induce the high velocity impact performance, but it resulted in the reduction of the impact performance of glass-carbon fiber/epoxy due to the agglomeration of the GNPs. [ABSTRACT FROM AUTHOR]

In this study, the wear behavior of Al2024 and composite materials produced by the stir casting method of Al 2024-0.2 (50% MgO + 50% CNT) was investigated. A mixture of 50% by weight of Magnesium oxide (MgO) with an average diameter of <40 nm and a 50% multi-walled carbon nanotube (MWCNT) 1.5 µm in length and 9.5 nm in diameter were used as reinforcement. Al was added in the melting pot as matrix material and continued until the liquid temperature rising to 750 °C. During the melting process, reinforcements were added into the melting pot and the mixing velocity was slowly increased to 500 rpm. The reinforcement material MgO and CNT were mixed in the liquid matrix. Mixing was continued at 500 rpm for about 10 minutes to have a homogeneous distribution of the reinforcements in the composite. The melting crucible was removed and left it at room temperature to cool. The hardness analysis performed, and abrasive wear behavior of composites have been investigated at different sliding distances (250m-500m-1000m) under 2N and 5N loads. The hardness of the materials has been increased with the doping of the reinforcing mixture. The hardness value of Rockwell F was improved up to 69 HRF with the addition of MGO and CNT. In the abrasion tests performed at 2 N loading and 1000 m sliding distance, wear of Al 2024 was 0.0039 gr, while the wear of hybrid composite was 0.0037 gr. Abrasion tests performed at 5 N loading and 1000 m sliding distance, the wear of Al 2024 was 0.0072 gr, while the wear of hybrid composite was 0.0049 gr. The added reinforcing mixture significantly reduced the abrasion weight loss of the material. [ABSTRACT FROM AUTHOR]

Laser Powder-based Directed Energy Deposition (LP-DED) process is a cutting-edge Additive Manufacturing (AM) technology for metal part repair and production. The disruptive potentialities of LP-DED are nowadays limited by the difficulty in the identification of the optimized set of process parameters, typically obtained from long and expensive experimental trials. In this work, a thermal simulation tool able to predict material deposition behaviour is developed using a finite element code. An original method is defined to model the material addition and energy flow. The forecasting capabilities of the model in terms of penetration depth and track dimensions are evaluated by comparing the numerical outcomes with experimental data. [ABSTRACT FROM AUTHOR]

Closed cell aluminium foams are highly pursued, due to their unique combination of properties. However, the current applicability of the aluminium foams is limited due to issues like high costs, density-gradient and brittleness of the cell walls, which are either related to use of metallic hydride as blowing agent or liquid-state processing. To address these issues, this study presents a first attempt to use polymer as a blowing agent to foam an aluminium alloy. A polymer is Poly (methyl hydro siloxane) was dispersed into an Al2024 sheet of 6 mm by Friction Stir Processing, in a localised region. This processed sample was pyrolysed at temperatures between solidus and liquidus (500–640 °C) of the alloy and at various durations (5–60 min) to foam the localised precursor. The density of resulting foams was measured by the Archemidies method and the resulting pore structures were characterised by Scanning Electron Microscopy (SEM) and micro X-ray Computed Tomography (CT). The results show that by as pyrolysis temperature increases relative density reaches a minimum of 0.65 at 560 °C. Beyond 590 °C, relative density increased from the optimum due to escape of foaming gasses. With increasing pyrolysis temperature, the pore size increased from few microns to several hundred microns. Further, quasi-static compression test was done on as processed, solutionized and aged foams. Due to increased strain hardening in aged samples energy absorbed during compression increased by 80% in the plateau region. Hence, polymeric a blowing agent can be used to synthesize heat-treatable foams with controllable absorption energy. [ABSTRACT FROM AUTHOR]

The control of a homogeneous distribution of the reinforcing phase in aluminum matrix composites is the main issue during the synthesis of this kind of material. In this work, 2024 aluminum matrix composites reinforced with boron carbide were produced by mechanical milling, using 1 and 2 h of milling. After milling, powdered samples were cold consolidated, sintered and T6 heat treated. The morphology and microstructure of Al2024/B4C composites were investigated by scanning electron microscopy; analysis of X-ray diffraction peaks were used for the calculation of the crystallite size and microstrains by the Williamson-Hall method. The mechanical properties were evaluated by compression and hardness tests. B4C particles were found to be well dispersed into the aluminum matrix as a result of the high-energy milling process. The crystallite size of composites milled for 2 h was lower than those milled for 1 h. The hardness, yield strength and maximum strength were significantly improved in the composites processed for 2 h, in comparison to those processed for 1 h and the monolithic 2024 alloy. [ABSTRACT FROM AUTHOR]

• Mechanical testing of Al2024 and Al7075 specimens using various test configurations leading to different failure modes are reported. • A meticulous method for constructing the damage initiation curves and their implementation in the finite element framework is given. • The ingredients required to predict failure initiation using four different ductile failure criteria are computed using finite element modelling and a comparison between the different criteria is reported. • A set of independent, complex mechanical experiments that challenge the failure criteria's prediction capabilities following initial calibration is performed. Predicting ductile failure in engineering structural components has been an active research topic for decades. Although the micro-mechanical phenomena that govern ductile failure are well understood, and many failure criteria proposed, a leading criterion has yet to be agreed upon. In the current study, four different ductile failure criteria were implemented in the finite element framework and used to study the ductile failure process of Al2024 and Al7075 specimens. The failure criteria included stress based, energy based and strain based formulations. Several different sets of experiments were first used to determine the different model parameters required to predict failure initiation. Then these same parameters were used to predict failure initiation for a different set of experiments with different geometries and under a complex stress and strain state. A critical analysis of the performance of the different ductile failure criteria was then conducted. It is shown that, while the stress based criteria fail to provide accurate predictions for the general loading case, the energy based and strain based criteria perform well and predict both the failure load and crack location. [ABSTRACT FROM AUTHOR]

The traditional methods for fatigue characterization of metallic materials are expensive and extremely time consuming. In order to overcome these shortcomings, the Thermographic Method (TM), based on thermographic analysis, is applied to estimate the fatigue limit of Al 2024. The temperature increase due to localized microplasticity is considered as the fatigue damage indicator. An experimental program is carried out to assess the fatigue limit both as resulting from the S–N field and, directly, from thermographic measurement. For the latter, three different methods are applied for the estimation of the AL 2024 fatigue limit and the out-coming results discussed. The values of fatigue limit predicted from the thermographic method according to the three methods are in good agreement to that derived from the traditional S-N procedure.

In this paper, ambient temperature (room temperature) accumulative roll bonding (ARB) is performed on Al2024 aluminum alloys to assess grain refining phenomenon. The microstructural evaluations show reduction in the grain size from about 25 μm to about 350 nm by a factor of ∼70 upon six cycles of ARB; X-ray diffraction patterns were used to assess the increase in the dislocation density. The yield and tensile strength of the ultrafine grained Al2024 after the sixth cycle, 465 and 492 MPa, were about 650 and 186% higher than that of the as-received sample, 62 and 172 MPa, respectively. Investigating the fractured surfaces of the tensile test specimens by scanning electron microscopy showed that ARB process alters the mode of fracture substantially; fracture surface of annealed sample consists of deep equiaxed dimples which is an indication of ductile fracture. However, this changes in the ARBed specimens to shear ductile rupture with shallow and small elongated dimples. [ABSTRACT FROM AUTHOR]

In this research surface nano composite of aluminum 2024 and boron carbide particles with the average size of 60 nm was fabricated by the friction stir processing (FSP) method. The primary friction stir processing tests showed that the rotating speed of 850 rpm and traverse speed of 25 mm/min are the optimum conditions which result in sound samples. The effects of nano - particle addition and number of passes were analyzed in the fabricated samples. Optical and field emission scanning electron microscopy techniques showed that the average grain size in the stir zone decreases by adding nanoparticles or increasing the number of FSP passes. The hardness and the abrasion tests showed that strength and wear resistance of the fabricated samples increases with the increase in number of passes. The improved mechanical properties were attributed to the grain refinement as well as the uniform distribution of nano-particles in the matrix. However, in the absence of nano-particles the hardness decreased due to the dissolution of primary particles in the stir zone. The result of electrochemical tests indicated that corrosion behavior of the FSPed samples improves by adding the nano - particles or increasing the pass number [ABSTRACT FROM AUTHOR]

A novel empirical constitutive law for thermo-viscoplasticity is proposed, which considers isotropic strain and strain rate hardening as well as thermal softening. The yield stress considers strain rate and thermal effects independently for the initial yield stress and the (strain) hardening stress. To date, most plasticity models consider strain rate and temperature effects only combined for the initial and hardening stress, which is not sufficient for several materials. Seidt and Gilat (Int J Solids Struct 50(2):1781-1790, 2013) presented comprehensive experimental measurements for the aluminum alloy Al2024 including isothermal compression tests at low strain rates and various constant temperatures from room temperature to almost melting temperature as well as adiabatic compression tests at high strain rates (up to 10,900 s $$^{-1}$$ ). In contrast to established thermo-viscoplastic material models, the proposed model is suitable to describe the material behavior of Al2024 accurately over a large range of loading conditions, i.e. from small to large plastic strains, low and high strain rates, and from room temperature to melting temperature, which is validated by the experimental data of Seidt and Gilat (2013). Consequently, with the use of the proposed constitutive law a variety of applications can be modeled, e.g. bulk forming, hot working, chip formation during cutting processes, or crash simulations. It is in particular promising for applications where combined loading conditions occur, like high strain rates and high temperatures at the chip formation. [ABSTRACT FROM AUTHOR]

In this study, hexagonal boron nitride (h -BN) reinforced Al-based metal matrix nanocomposites were successfully prepared using a powder metallurgy-assisted high-energy ball milling and vacuum-hot pressing process. Al2024 alloy and h -BN nano-powders (at 0, 2, 3, 4, and 5wt%) were milled for 8 h to produce Al2024/ h -BN nanocomposites. The effect of h -BN nanoparticle content on the microstructure, density, hardness, tensile strength, wear, and corrosion behavior of Al2024/ h -BN nanocomposites was investigated. It was observed that the h -BN powders in the Al2024/ h -BN nanocomposites were homogeneously distributed up to a content of 4 wt%, beyond which the h -BN aggregated at the grain boundaries due to excessive reinforcement. The uniform distribution of h -BN nanoparticles in the Al2024 matrix had a positive effect on the mechanical properties and wear and corrosion behavior of the Al2024/ h -BN nanocomposites. The results showed that the highest values of hardness and tensile strength were 126 HB and 299.72 MPa, respectively, in the 4 wt% h -BN reinforced sample. The wear volume loss decreased significantly as the h -BN reinforcement content increased up to 4 wt %. The corrosion experiment results showed that the corrosion resistance of the 4 wt % h-BN reinforced nanocomposite, which had the lowest polarization resistance of 15.22 Ω cm2, was almost 5 times higher than that of the unreinforced Al2024 alloy. • Al2024/h-BN nanocomposites were produced in a near defect-free manner. • The hardness of the nanocomposites increased up to 4 wt% of h-BN content. • As the amount of reinforcement increased up to 4 wt%, the wear volume loss decreased. • The electrochemical measurements of the nanocomposites were carried out in 3.5% NaCl solution. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop a production process of a fine globular structure feedstock of the 2024 aluminumalloy suitable for subsequent semi-solid forming. The 2024 wrought aluminum alloy was first annealed to reduce the effect ofwork hardening. Then, strain was induced in the alloy by cold compression. After that the microstructural evolution duringpartial melting was investigated. The samples were subjected to full annealing at 415°C for 3 hrs prior to cold compression of40% reduction of area (RA) with 3 mm/min strain rate. After that samples were partially melted at 620°C with varying holdingtime from 0 to 60 min followed by water quenching. The grain size and the average grain diameter of solid grains weremeasured using the linear intercept method. The globularization was interpreted in terms of shape factor. Liquid fraction andthe distribution of the eutectic liquid was also investigated. It was found that during partial melting, the globular morphologywas formed by the liquid wetting and fragmentation of high angle boundaries of recrystallized grains. The suitable semi-solidmicrostructure was obtained from a condition of full annealing, 40% cold working and partial melting at 620°C for 6 minholding time. The near globular grains obtained in the range of 0-60 min consisted of uniform spheroid grains with an averagegrain diameter ranged from 73 to 121 m, quenched liquid fraction was approximately 13–27% and the shape factor was greaterthan 0.6. At a holding time of less than 6 min, grain coarsening was dominant by the immigration of high-angle grainboundaries. At a longer holding time, liquid fraction increased and Ostwald ripening was dominant. The coarsening rateconstant for the 2024 Al alloy was 400.36 mm3.s-1. At a soaking time of 60 min, it was found that a minimum diameter differencewas 1.06% with coarsening index n=3 in a power law equation. The non-dendritic slug of 2024 alloy was rapid compressedinto a disc with 90%RA and exhibited uniform structure.

The control of a homogeneous distribution of the reinforcing phase in aluminum matrix composites is the main issue during the synthesis of this kind of material. In this work, 2024 aluminum matrix composites reinforced with boron carbide were produced by mechanical milling, using 1 and 2 h of milling. After milling, powdered samples were cold consolidated, sintered and T6 heat treated. The morphology and microstructure of Al2024/B4C composites were investigated by scanning electron microscopy; analysis of X-ray diffraction peaks were used for the calculation of the crystallite size and microstrains by the Williamson–Hall method. The mechanical properties were evaluated by compression and hardness tests. B4C particles were found to be well dispersed into the aluminum matrix as a result of the high-energy milling process. The crystallite size of composites milled for 2 h was lower than those milled for 1 h. The hardness, yield strength and maximum strength were significantly improved in the composites processed for 2 h, in comparison to those processed for 1 h and the monolithic 2024 alloy.

Machining experiments were conducted to evaluate the impact of cutting parameters on the hole quality and cutting forces in drilling Al2024-T3 aerospace alloy. Al2024-T3 specimen were drilled using Φ6-mm TiAlN-coated carbide twist drills under dry cutting conditions. The hole quality was inspected in terms of its surface roughness, burr and chip formations, hole size, circularity error and post-machining microhardness of the subsurface of the holes. An analysis of variance (ANOVA) was carried out to determine the percentage contribution of cutting parameters on cutting forces and the inspected hole quality parameters. A three-dimensional (3D) finite element (FE) model of drilling Al2024-T3 is developed using Abaqus/Explicit to predict thrust force and torque. The FE model was validated using experimental results and found to be in good agreement. The results of the study showed that the cutting parameters have a significant impact on cutting forces and inspected hole quality parameters. Drilling at feed rates of 100 and 300 mm/min and spindle speeds of 1000, 3000, and 6000 rpm are recommended for producing holes with smaller surface roughness, deviation from nominal hole size, circularity error and burrs. [ABSTRACT FROM AUTHOR]

Abstract: A new approach was used to produce Al–10%Al2O3 surface nanocomposite on Al2024 substrate. This novel approach involved air plasma spraying of Al–10%Al2O3 powder to produce Al–10%Al2O3 coating on substrate. The coated material was then subjected to friction stir processing (FSP) to distribute Al2O3 particles into the substrate. Microstructure and mechanical properties of samples were investigated by optical microscopy (OM), scanning electron microscopy (SEM), micro-hardness and wear measurements. As a result, it was found that the Al2O3 particles were distributed uniformly inside the substrate with an average penetration depth of about 600μm. The surface nanocomposites produced in this way had excellent bonding with the substrate. The micro-hardness of the surface nanocomposite was ∼230Hv, much higher than ∼90Hv for Al2024 substrate. The surface nanocomposites also exhibited lower friction coefficient and wear rate. It was found that the addition of Al2O3 nanoparticles to the Al2024 matrix alloy affect the mechanism of wear. [ABSTRACT FROM AUTHOR]

Local melting of eutectic films and cracking is found in Al 2024 and Al 7075 alloy friction stir spot welds. Dissolution of melted films removes all evidence melted film formation in spot welds made using typical welding parameter settings. For this reason friction stir spot welding is carried out at a rapid plunge rate of 10 mm s-1 and an extremely short dwell time of 0·05 s and after tool retraction, the welded samples are rapidly quenched using a mixture of methanol and liquid nitrogen at a temperature of -80°C. Eutectic films rich in Zn and Cu are formed in Al 7075 spot welds while melted Al2CuMg particles promote the formation of α-Al+Al2CuMg eutectic films in Al 2024 spot welds. Melted eutectic formation and cracking is also observed beneath the tip of the rotating pin during Al 7075 friction stir spot welding and is consistent with the occurrence of melt wear in this location. [ABSTRACT FROM AUTHOR]

Abstract: The effects of volume fraction and size of SiCrFe, CrFeC, and Al2O3 particulates on the abrasive wear rate of compo-casted Al2024 metal matrix composites (MMCs) were studied. The process variables like the stirring speed, position and the diameter of the stirrer have affected the diffusion between particulates and matrix. The abrasive wear rate was decreased by the increase in particulate volume fraction of SiCrFe and CrFeC intermetallic reinforced composites over 80 grade SiC abrasive paper. The wear rates of the all composites decreased with aging treatment, and the best result was seen for the composite having a hybrite structure as SiCrFe and CrFeC particulates together. Nevertheless, the fabrication of composites containing soft particles as copper favors a reduction in the friction coefficient. [Copyright &y& Elsevier]

The integrity of machined holes depends on many parameters, some of which are related to the cutting tool (geometry, coating, material). Other influential parameters are related to the machining process variables (spindle speed, feed rate, workpiece material), all of which can affect the quality of the hole and drilling induced damage on its surface. This study investigates the effect of uncoated tools and four types of tool coatings (TiN-, TiCN-, TiAlN-, and TiSiN) on the hole quality and its microstructure. The study analyzed several hole geometrical metrics, namely hole size, circularity, cylindricity, and perpendicularity of an Al2024 aluminum alloy using a multi-spindle drilling process that utilizes three drills capable of creating multiple holes simultaneously. The results showed that the uncoated carbide drill gave a high-hole quality at low spindle speed. Regarding the coated drills, TiCN coated drills produced holes with the least deviation, circularity, cylindricity and perpendicularity at high spindle speeds. TiSiN–carbide coated drills produced the most oversized holes and noticeable damage and deformations on their surface following TiAlN and TiN. The common surface damage found on the inner hole surface was smearing, feed marks, and metal debris adhesion. The ANOVA results revealed that the tool type had the highest percentage contribution that mainly affected the hole quality. [ABSTRACT FROM AUTHOR]

Halogen-free, N/P-containing ionic liquid (NP-IL) was synthesized by combining bis-quaternary ammonium cations with phosphate ester anions and were compared to polyalphaolefin 10 (PAO 10), and a halogen-containing IL (BMIMPF 6). The corrosive properties of the NP-IL, BMIMPF 6 , and PAO 10 lubricants were evaluated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The corrosion performance tests show that NP-IL has better corrosion resistance than that of BMIMPF 6 due to its halogen-free characteristics. The tribological performances of NP-IL, BMIMPF 6 , and PAO 10 were evaluated by Optimol SRV-V oscillating friction tester. The lubricant mechanism of NP-IL was evaluated using SEM, EDS, X-ray photoelectron spectroscopy (XPS), and by time-of-flight secondary-ion mass spectrometry (TOF-SIMS). From the results, the NP-IL was found to be a suitable lubricant for steel–Al2024 friction contacts. During friction, the IL forms a surface-protective film thought tribochemistry, which contributes to reduce-friction (RF) and anti-wear (AW). • NP-IL ensures very-low wear corrosion when it is applied to aluminum alloys. • NP-IL has excellent tribological property for steel/aluminum friction contacts. • Lubricating film improves tribological property for steel/aluminum friction contacts. [ABSTRACT FROM AUTHOR]