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Abstract Lightweight aluminium matrix composites find wide applications in automobile and aerospace sector. Aluminium alloy composites with graphene nanoplatelets (GNPs) were prepared by powder metallurgy route containing four different loadings, i.e. 0.1 wt%, 0.5 wt%, 1 wt% and 3 wt%. Two methods for exfoliation of GNPs were employed to achieve uniform dispersion in Al6061 matrix. Pressureless consolidation followed by sintering was carried out to obtain near-theoretical densities. Comparison of the fabricated thermal condition and artificially aged T6 samples was carried out to investigate the contribution of GNPs in the strengthening of Al6061 matrix. Microstructure evolution was confirmed by X-ray diffraction, optical and scanning electron microscopy. Electrical conductivity increased with increasing content of GNPs up to 1 wt% due to conductive network around the matrix grains. Mechanical properties were found to increase 93%, 61% and 92% in hardness, compression strength and flexural strength up till 1 wt% GNPs in matrix alloy. Agglomeration at 3 wt% GNPs resulted in deterioration of properties. The fractured surfaces were examined to determine the change in fracture morphology, associated strengthening mechanism and behaviour of GNPs. Highlights • Dual dispersion technique for dispersion of GNPs is utilised. • GNPs are incorporated in fabricated and artificially aged Al6061 matrices. • GNPs contribution in ductile and hardened matrices is established for the first time. • A mathematical model for predicting the contribution of GNPs is proposed. • An illustrative model of GNPs and crack propagation is developed. [ABSTRACT FROM AUTHOR]

Due to the momentous advantages of composite materials, recent years many studies focused on reinforcing different new materials to the existing ones to improve their conventional strength and life time within the concern of application status. In the row, reinforcements on Al6061 become a fancy topic among researchers due to its wide applications including automobiles, yachts, electrical fittings and so on. This study continues this innovation by reinforcing three different reinforcement materials including zirconia (ZrO2), zirconia + aluminium oxide (ZrO2 +Al2O3) and fused zirconia aluminum (40FZA). These three reinforcing materials are included with the proposition of varying particle reinforcements as 5, 10 and 15%. The testing specimens were experimented to explore its mechanical, wear and corrosion behavior. Further the experimental results are given as inputs to the numerical analysis, PROMETHEE. By combining the experimental and numerical methodologies the reliability of the results were improved. However, from this study it can be evident that inclusion of 15% particle reinforcement of zirconia fused alumina in Al6061 provides greater strength, toughness, high resistance to wear and corrosion on both experimental and numerical analysis. There is ample room that this proposed material inclusion be a better option for the reinforcement of Al6061 among available alternatives for sustainable development. [ABSTRACT FROM AUTHOR]

Abstract Aluminum-based metal matrix composites (MMCs) are useful materials for structural applications due to their high strength to weight ratio. In this study, the addition of the rare earth element La to the Al6061 alloys as in-situ La oxide dispersoids fabricated by mechanical alloying was investigated. The result shows that an increase of La content can change the morphology of synthesized powders and has significant influence on microstructure uniformity, hardness, densification, and ductility of the materials. The results also show that the complex La-Al-Si-O oxides and needle-like AlFeSi intermetallic compounds were formed during ball milling and subsequent sintering processes. Highlights • In-situ La oxide dispersoids are formed during ball milling. • Addition of La can change the morphology of milled powders. • Fine La-Al-Si-O oxides and needle-like AlFeSi phases are found. • Low La content alloys have a dense and uniform microstructure. • High hardness and modulus are obtained at low La content alloys. [ABSTRACT FROM AUTHOR]

The present work deals with conduction of wear test on Al6061/eggshell composites with load, reinforcement and sliding distance as control factors and its regression analysis. Chicken eggshell is one of the most abundant natural waste products generated in large amount by food processing industry due to its everyday consumption. This material is simply disposed in nature thus constituting environmental hazards. Commercial use of eggshells can produce lightweight materials at low cost. Therefore, being complemented with less dense calcium carbonate, it can be used as reinforcement to develop metal matrix composite using stir casting process. Reinforcement is added in the range of 2-10 wt% at an interval of 2%. Optical microstructural characterization indicated fair distribution of particles in the matrix, and 4 wt% composite exhibited best properties among all. Further addition of particles proved to be detrimental due to increase in porosity and agglomeration of particles. Wear track and debris were examined with scanning electron microscope to explain the wear process. Regression analysis helped in establishing the relationship between the control factors. Reinforcement of eggshell particles improved the wear resistance of matrix significantly as suggested by analysis of variance. [ABSTRACT FROM AUTHOR]

Aluminum composite matrix materials are regarded as the most popular type of composite materials. Metal matrix composites made of aluminum have better mechanical and thermal properties, including a higher strength-to-weight ratio, tensile strength, hardness, and a low coefficient of thermal expansion. In various types of applications viz, automobile, aviation, the thermal characterization of aluminum metal matrix composites has increased. Thermal conductivity as a function of temperature, thermal diffusivity, and the thermal gradient is one of the essential thermal characteristics of aluminum metal matrix composites needed to understand the material’s behavior. The current work evaluated thermal conductivity as a product of thermal diffusivity, density, and specific heat for Al6061/Ni/Cr hybrid nano metal matrix composites from 50 °C to 300 °C. Al6061 based metal matrix composite reinforced with varying wt.% of Ni and Cr nanoparticles whereas fixed wt.% of graphene and Mg added to improve thermal conductivity, self-lubrication, and wettability. Thermal diffusivity, specific heat, and density were evaluated using laser flash apparatus (LFA 447), differential scanning calorimetry (DSC), and Archimedes principle, respectively. Results revealed that the thermal conductivity of fabricated composites increases with Ni, Cr, Mg, and graphene nanoparticles. With further expansion of reinforced particles of Ni and Cr, the thermal conductivity decreases. Finite element analysis (FEA) has been conducted to determine the thermal gradient and thermal flux using experimental values such as density, thermal conductivity, specific heat, and enthalpy at various temperature ranges to validate the experimental results.

Today, in the world of materials the focus is on the development of metal matrix composites (MMC’s), particularly aluminium based composites due to its widespread applications in aerospace and automobile industries. To develop light weight MMC’s, carbon fibres in both continuous and dis-continuous forms are used as reinforcements. The processing and characterization of mechanical and adhesive wear behaviour of various composites are widely practiced by various researchers around the world. However, solid erosion wear of continuous carbon fibre reinforced MMC’s has not yet been reported. In the light of the above, the present work focuses on characteristics of erosive behaviour of Al6061-carbon fibre rods composites developed by casting route. Carbon fibre rods of 4 mm and 6 mm diameters were surface sensitized to achieve electroless nickel coating followed by copper electroplating on the nickel coated rods and were used as the reinforcements to develop the composites. An air jet erosion rig made according to ASTM G76 standard configuration was used to conduct the tests. The effect of carbon fibre reinforcement, test duration and angle of impingement of the erodent on the erosion wear behaviour of the developed will be discussed at length.

In the present paper an attempt is made to establish a response surface methodology based non-linear mathematical model for the friction-wear behaviour of as cast and heat-treated Al6061/9%Gr/WC (with WC at 1, 2 and 3 wt%) metal matrix composites (MMCs). During experimentation, the process parameters, namely percentage of WC, load, sliding distance and sliding velocity have been considered as inputs and wear loss (WL) and coefficient of friction (COF) have been treated as the responses. Results reveal that, for as-cast Al6061/9%Gr/WC hybrid composites, the WL decreases with increase in percentage of WC and increases with the increase in load, sliding distance and sliding velocity. Moreover, COF decreases with increase in percentage of WC and sliding velocity and increases with increase in the load and sliding distance. It has also been observed that the WL and COF of heat treated composites are found to be less than the as cast MMCs. Further, fuzzy grey relational analysis (GRA) has been used to perform the multi objective optimization of the said wear process. Finally, the evidence of wear phenomenon for the said composites have been examined with the help of scanning electron microscopy. [ABSTRACT FROM AUTHOR]

In the present investigation, a newly fabricated Al6061 reinforced with various quantity (0.4-1.6 wt%) of nano SiC in steps of 0.4 and fixed quantity (0.5 wt%) of micro graphite particle’s hybrid nanocomposites were prepared by ultrasonic assisted stir casting method. The influence of nano SiC and graphite content on the mechanical and tribological properties of Al6061 hybrid nanocomposites were studied. The pin-on-disc equipment was used to carry out experiment at 10-40 N applied load, 0.5 m/s sliding speed and 1000 m sliding distance. The Al/SiC/Gr hybrid nano-composite and matrix alloy wear surfaces were characterized by FESEM equipped with an EDS, 3D profilometer to understand the wear mechanisms. The results of Al/SiC/Gr self-lubricating hybrid nano-composites showed improved wear resistance than the Al6061 matrix alloy. The co-efficient of friction of Al/SiC/Gr hybrid nano-composites were lower than those of the unreinforced alloy at various applied load. Compared to matrix alloy, the surface roughness of Al/SiC/Gr hybrid nano-composites had significantly reduced to 66% at low load and 75% at high load. Self-lubricating Al/SiC/Gr hybrid nanocomposites showed superior surface smoothness compared to matrix alloy. [ABSTRACT FROM AUTHOR]

The present work investigated the influence of speed, feed, depth of cut and weight fraction on acceleration amplitude in end milling of Al6061-SiC metal matrix composite. Five specimens in various reinforcement weight fractions (0 %, 5 %, 10 %, 15 % and 20 %) were fabricated using stir casting method. The milling tests were performed based on Taguchi’s L 25 orthogonal array and a parametric investigation was carried out. Analysis of variance (ANOVA) results showed that the feed was the most significant milling parameter affecting acceleration amplitude followed by weight fraction, depth of cut and speed. [ABSTRACT FROM AUTHOR]

In this study, new generation hybrid composite materials were produced by adding SiC, h-BN and Graphite (Gr) to the Al6061 alloy, which has light, corrosion resistant, good formability and weldability properties, giving it abrasion resistance and high strength properties. Five different reinforced and non-reinforced samples were produced, namely Al6061, Al6061%10SiC, Al6061%8SiC%2 h-BN, Al6061%8SiC%2Gr, and Al6061%8SiC%1 h-BN%1Gr, by the hot extrusion method. The density, hardness, microstructure, tensile strength, transverse rupture strength (TRS), and abrasion properties of the synthesized samples are reported in this study. While small agglomerations were observed in the composite materials (10%SiC) produced with a single reinforcement element, it was almost absent in the hybrid composite materials. The hardness of the SiC- and h-BN-containing composites were higher than those of Al6061. The tensile strength and TRS improved relative to those of the reinforcement elements. The addition of h-BN and Gr improved the wear properties. [Display omitted] • In this study, hybrid composite materials with Al6061 matrix, SiC, h-BN and Graphite particle addition were successfully produced with high density by hot extrusion technique. • Density, hardness, microstructure, tensile strength, cross fracture strength and abrasion properties of the produced composite materials were compared. • Analysis of broken surface after tensile test and analysis of worn surfaces after wear were interpreted with the help of SEM and EDS. • Added SiC, h-BN and Graphite reinforcement elements improved in hardness, tensile strength, transverse rupture strength and wear properties. [ABSTRACT FROM AUTHOR]

This paper describes the study of effect of aging on mechanical and wear properties of ‘hot rolled’ Al6061-10% wt. of beryl particulate reinforced composites produced by stir casting have been examined. The result shows that hardness and tensile strength of ‘90% hot rolled and aged’ composites were increased by 10.28% and 3.78% as compared to ‘hot rolled’ composites respectively. The ‘hot rolled and aged’ composite shows significant decrease in specific wear rate when compared to that of ‘hot rolled’ composites.

Composite materials have the capability of being customised to provide specific mechanical and tribological properties. This paper presents the manufacture of a novel composite of Al6061 with 5% SiC (50 μm size) by the stir casting method. Experimental investigations of mechanical and tribological properties of SiC reinforced Al6061 are discussed. Investigations with a Rockwell hardness tester revealed that this composite had enhanced hardness. Wear characteristics were investigated for Al6061 and the novel composite Al6061 + SiC with a Pin on disc tribometer for a load range of 5N-200N and RPM varying from 200 to 1500. The effect of crucial parameters such as load and RPM on the wear of the novel composite were presented with sensitivity analysis. The results obtained are encouraging, showing the novel composite having a lower wear rate.

Additive manufacturing (AM) offers customization of the microstructures and mechanical properties of fabricated components according to the material selected and process parameters applied. Selective laser melting (SLM) is a commonly-used technique for processing high strength aluminum alloys. The selection of SLM process parameters could control the microstructure of parts and their mechanical properties. However, the process parameters limit and defects obtained inside the as-built parts present obstacles to customized part production. This study investigates the influence of SLM process parameters on the quality of as-built Al6061 and AlSi10Mg parts according to the mutual connection between the microstructure characteristics and mechanical properties. The microstructure of both materials was characterized for different parts processed over a wide range of SLM process parameters. The optimized SLM parameters were investigated to eliminate internal microstructure defects. The behavior of the mechanical properties of parts was presented through regression models generated from the design of experiment (DOE) analysis for the results of hardness, ultimate tensile strength, and yield strength. A comparison between the results obtained and those reported in the literature is presented to illustrate the influence of process parameters, build environment, and powder characteristics on the quality of parts produced. The results obtained from this study could help to customize the part’s quality by satisfying their design requirements in addition to reducing as-built defects which, in turn, would reduce the amount of the post-processing needed.

This study investigates the optimization of CNC turning operation parameters for Al6061 nickel coated graphite (NCG) metal matrix composite using the Taguchi based grey relational analysis method. The turning operations are carried out with carbide cutting tool inserts. According to the Taguchi quality concept, 3-level orthogonal array was chosen for the experiments. The experiments are conducted at three different cutting speeds (125, 175, 225m/min) with feed rates (0.1, 0.15, 0.2mm/rev) and depth of cut (0.5, 1, 1.5mm) and different % of reinforcement (2.5%, 5%, 7.5%), signal to noise ratio and the analysis of variance are used to optimize cutting parameters. The effects of cutting speed, feed rate and depth of cut on surface roughness and MRR are analyzed. Mathematical models are developed by using the response surface method to formulate the cutting parameters experimental results shown that machining performance can be improved effectively by using this approach, the analysis of variance (ANOVA) is applied to identify the most significant factor for the turning operations according to the weighted sum grade of the GRG. The predict responses shows the models have more than 95% of confident level of R2 value, from the obtained confirmation experiment result, it is observed, there is a good agreement between the estimated value and the experimental value of the grey relational grade. This experimental study reveals that the grey-Taguchi and RSM can be applied successfully for multi response characteristic performances. [ABSTRACT FROM AUTHOR]

The present work is focused on the investigations on dry sliding wear behaviour of aluminium metal matrix composite at room and elevated temperature. Aluminium metal matrix composites reinforced with red mud are prepared by stir casting method. The experiments are planned using Taguchi technique. An orthogonal array, analysis of variance and signal to noise ratio are used to check the influence of wear parameters like temperature, percentage of reinforcement, mesh size, load, sliding distance and sliding speed on dry sliding wear of composites. The optimal testing parameters are found and their values are calculated which are then compared with predicted values. A reasonable agreement is found between predicted and actual values. The model prepared in the present work can be effectively used to predict the specific wear rate of the composites. [ABSTRACT FROM AUTHOR]

In present study, Red mud, an industrial waste, has been utilized as a reinforcement material to fabricate Aluminium 6061 matrix based metal matrix composite. Taguchi L18 orthogonal array has been employed for fabrication of composite castings and for conducting the tribological experimentation. ANOVA analysis has been applied to examine the effect of individual parameters such as sliding condition: dry and wet, reinforcement weight fraction, load, speed, and sliding distance on specific wear rate obtained experimentally. It has been found that tensile strength and impact energy increases while elongation decreases, with increasing weight fraction and decrease in particle size of red mud. The percentage contribution of the effect of factors on SWR is Sliding condition (73.17), speed (7.84), percentage reinforcement (7.35), load (5.75), sliding distance (2.24), and particle size (1.25). It has also been observed that specific wear rate is very low in wet condition. However, it decreases with increase in weight fraction of reinforcement, decrease in load and sliding speed. Al6061/red mud metal matrix composites have shown reasonable strength and wear resistance. The use of red mud in Aluminium composite provides the solution for disposal of red mud and can possibly become an economic replacement of Aluminium and its alloys. [ABSTRACT FROM AUTHOR]

The present study deals with tapping of Al6061/SiC metal matrix composite. Stir casting technique was used for the fabrication of composite. Castings were produced by varying weight percentage of SiC (5, 7.5 and 10 wt. %) of 23 µm size in Al6061. The fabricated specimens were characterized for their hardness and tensile strength. It was found that hardness increases by the addition of SiC. Images from Scanning Electron Microscope (SEM) and metallurgical microscope showed the fair distribution of reinforcement. Due to the presence of SiC reinforcement that is highly abrasive in nature makes machining difficult and produces high rate of tool wear. After drilling, tapping experiments were conducted for the machinability study of Al6061/SiC metal matrix composite by using M8 HSS machine tap. Tapping operation was performed under dry condition with different cutting speed (12, 14 and 16 m/min) and constant feed rate equal to the pitch of thread. Torque required for tapping was measured using strain gauge based two-component cutting tool dynamometer. Microstructure and surface morphology of thread surfaces was analyzed using Metallurgical Microscope and Scanning Electron Microscope (SEM) respectively. Estimation of progressive flank wear of machine taps was undertaken using profile projector. The performance of HSS machine taps was evaluated in terms of tapping torque, tool flank wear and surface characteristics of thread surfaces. [ABSTRACT FROM AUTHOR]

This paper investigated the compression behaviour of Al 6061-T6 alloys at various high strain rates through split Hopkinson pressure bar (SHPB) experiments. The compressive strength (σ c ) of Al 6061-T6 alloy was measured in the present work as a function of high strain rate ε ̇ . The measurements were done in the strain rate regime of 3 × 10 3 to 6.5 × 10 3 s − 1 . The results showed that the corresponding (σ c ) increased exponentially with increase in ( ε ̇ ). But, the increase in strain with increasing ε ̇ was primarily linear. The work hardening coefficient decreased with the increase of strain. However, the decrease of work hardening coefficient with increasing strain rate did not follow a similar trend. With the increase of ε ̇ the strain rate sensitivity increased. As expected, the thermal activation volume decreased with increase in ε ̇ . Using the Zerilli-Armstrong equation attempt was made to evaluate the related material constants to predict the stress-strain curves. The predicted stress-strain behaviours matched reasonably well with those measured experimentally in the current SHPB experiments. The implication of these results in engineering design and simulation in the context of resisting high strain rate impact was also discussed. [ABSTRACT FROM AUTHOR]

The reinforcement particles play important roles in determining microstructural development and properties of Al6061 composites. In the present work, the aging behavior of Al6061 reinforced with Y2O3 and TiC particles produced via mechanical alloying are investigated. The results indicate that the peak-aged Al6061 alloy without reinforcement demonstrates the highest hardness, which corresponds to the formation of theMg-Si precipitates. However, precipitation formation is not observed in the case of the Al6061 composites, which can be attributed to the fact that the Mg-Si clusters and GP zones are inhibited by the presence of the reinforcement particles. The solute elements segregate in the complex oxides or carbides and contribute to only a slight increase in hardness. [ABSTRACT FROM AUTHOR]

Recent studies are evaluating the use of particulates fabricated from agro-based residues as reinforcement for enhancing the properties of aluminium alloys. This report focuses on the optimization approach and modeling of responses for future prediction, which are absent from the majority of studies involving particle reinforcement of an aluminum matrix. Herein, palm kernel shell ash (PKA) and rice husk ash (RHA) were incorporated with 4 wt% of WSD and used as fillers in the Aluminium-6061 matrix at variable proportions. The response surface approach was utilized in the experiment design, modeling, and outcome optimization. The independent variables are the proportions of PKA and RHA and stir casting temperature. Yield, ultimate tensile, impact strength, elastic modulus, and fracture toughness are examined as response parameters. The results demonstrated that the microstructural property played a significant role in the responses. Incorporating PKA and RHA into the Al-6061 matrix improved the response parameters. Temperatures in the range of 700 and 800 °C enhanced the property parameters, even though temperatures within 800 and 900 °C caused a decline in response. The dependence of the responses on the pattern between property variables was revealed by surface and contour plots. The development of models for predicting responses. Optimal conditions were reached at 4.03% PKA, 5.12% RHA, and 787 °C, with an error <5% when compared to the forecast responses, thus validating the model., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 Published by Elsevier Ltd.)

Additive manufacturing (AM) of high-strength Al alloys promises to enhance the performance of critical components related to various aerospace and automotive applications. The key advantage of AM is its ability to generate lightweight, robust, and complex shapes. However, the characteristics of the as-built parts may represent an obstacle to the satisfaction of the parts’ quality requirements. The current study investigates the influence of selective laser melting (SLM) process parameters on the quality of parts fabricated from different Al alloys. A design of experiment (DOE) was used to analyze relative density, porosity, surface roughness, and dimensional accuracy according to the interaction effect between the SLM process parameters. The results show a range of energy densities and SLM process parameters for AlSi10Mg and Al6061 alloys needed to achieve “optimum„ values for each performance characteristic. A process map was developed for each material by combining the optimized range of SLM process parameters for each characteristic to ensure good quality of the as-built parts. This study is also aimed at reducing the amount of post-processing needed according to the optimal processing window detected.

The demand for aluminum hybrid metal matrix composites has increased in recent times due to their enhanced mechanical properties for satisfying the requirements of advanced engineering applications. The performance of these materials is greatly influenced by the selection of an appropriate combination of reinforcement materials. The reinforcement materials include carbides, nitrides, and oxides. The ceramic particles, such as silicon carbide and aluminum oxide, are the most widely used reinforcement materials for preparing these composites. In this paper, an attempt has been made to prepare an Al6061 hybrid metal matrix composite (HAMMC) reinforced with particulates with different weight fractions of SiC and Al2O3 and a constant weight fraction (5%) of fly ash by a stir-casting process. The experimental study has been carried out on the prepared composite to investigate the mechanical properties due to the addition of multiple reinforcement materials. The density and mechanical properties, such as ultimate tensile strength, yield strength, impact strength, and the hardness and wear characteristics of the proposed composite, are compared with those of unreinforced Al6061. The experimental investigation is also aimed at observing the variation of properties with a varying weight percentage of the reinforcement materials SiC and Al2O3 simultaneously with the fly ash content maintained constant. The outcome of the experimental investigation revealed that the proposed hybrid composite with 20% of total reinforcement material exhibits high hardness, high yield strength, and low wear rate but no considerable improvement in impact strength.

The present work aims at optimization of the process parameter such as cutting speed, depth of cut and feed rate on surface roughness produced on the machined component. Analysis is carried out using Taguchi robust design principles. From the analysis, feed rate is found to be the most influential process parameters which influence the surface roughness followed by cutting speed and depth of cut. Increase in feed rate and depth of cut is found to increase the surface roughness. [ABSTRACT FROM AUTHOR]

Modern industries strive to improve the quality of their product by choosing proper materials and methods. Selection of materials of high strength to weight ratio like aluminum and setting of optimum machining parameters ensures the desired quality of product at affordable cost. Industries look for high productivity and better surface finish in machining operations which depends on process parameters. In this article the process parameters such as feed rate, cutting speed and depth of cut are selected to optimize the material removal rate in turning of Al-6061. The analysis is carried out using signal to noise ratio for predicting optimum process parameters. The effect of process parameters on material removal is discussed in this article. [ABSTRACT FROM AUTHOR]

Cold spray is a developing technology that is increasingly finding applications for coating of similar and dissimilar metals, repairing geometric tolerance defects to extend expensive part life and additive manufacturing across a variety of industries. Expensive helium is used to accelerate the particles to higher velocities in order to achieve the highest deposit strengths and to spray hard-to-deposit materials. Minimal information is available in the literature studying the effects of He-N mixing on coating deposition efficiency, and how He can potentially be conserved by gas mixing. In this study, a one-dimensional simulation method is presented for estimating the deposition efficiency of aluminum coatings, where He-N mixture ratios are varied. The simulation estimations are experimentally validated through velocity measurements and single particle impact tests for Al6061. [ABSTRACT FROM AUTHOR]

The reinforcement particles play important roles in determining microstructural development and properties of Al6061 composites. In the present work, the aging behavior of Al6061 reinforced with Y2O3 and TiC particles produced via mechanical alloying are investigated. The results indicate that the peak-aged Al6061 alloy without reinforcement demonstrates the highest hardness, which corresponds to the formation of the Mg–Si precipitates. However, precipitation formation is not observed in the case of the Al6061 composites, which can be attributed to the fact that the Mg–Si clusters and GP zones are inhibited by the presence of the reinforcement particles. The solute elements segregate in the complex oxides or carbides and contribute to only a slight increase in hardness.

The thermal and athermal influence of electric current on dislocation motion is the fundamental mechanism for the electroplastic effect in different metals. Due to the significant scale difference between dislocation evolution and macroscopic deformation, it is difficult to figure out how the electric current affects the dislocation motion and further leads to the macroscopic electroplastic behavior since several interweaving mobile and immobile dislocations are involved. As a macroscopic manifestation of the interaction between dislocations and interstitial atoms, the Portevin–Le Chatelier (PLC) effect provides a satisfying entry point for solving the above problems by connecting the microscopic dislocation mechanism to the macro-scale electroplastic effect in a straightforward manner. Experiments of Al6061 in the tensile process show that the introduction of current causes two opposite effects, i.e., an increase of the pinning strength and a reduction of the time for dislocations to escape from pinning. Further microscopic characterization reveals that the reasons for the above phenomena include two aspects: (1) Promotion of the dissolution of the precipitated phase and increases in the concentration of interstitial atoms in the system. (2) Promotion of the motion of dislocations and the activation of additional slip systems. Those changes are closely related to the thermal and athermal effects of the current. Based on the observation results in this paper, the contradictions in the existing literature can be well explained. [Display omitted] • Study on the influence of electric current on dislocation behavior based on the Portevin-le Chatelier effect. • The influence of currents on dislocation motion has two competing mechanisms related to thermal and athermal effects. • The research results successfully explained the contradictions in the existing research. [ABSTRACT FROM AUTHOR]

This paper describes an exploding wire experiment to measure the electrical specific action to melt of structural alloys of copper and aluminum, including C10100, C11000, C18000, C18200, Al6061, and Al7075. These alloys, which are commonly used in railguns and other pulsed power devices, are not produced in fine wire form. Instead of wires, we developed a technique to test macroscopic samples ( 0.25~mm\times 0.5~mm cross section) manufactured with wire electrical discharge machining. This paper includes a description of the design considerations for such macroscopic exploding wire experiments. [ABSTRACT FROM PUBLISHER]

This paper discusses tensile testing of small samples of nanocrystalline Al6061-T6 alloy obtained from an unusual application of machining as a severe plastic deformation process. Ultrafine grained (UFG) shavings obtained from plane-strain cutting show higher hardness than the bulk material in agreement with existing literature. Application of restricted contact tools and extrusion-machining was explored to obtain shavings with minimum curvature to aid in tensile test specimen preparation. A novel method to prepare small tensile test specimens from these shavings has been described. During the tensile testing of UFG material, strains were measured using digital image correlation of natural speckles on the specimen. Specimens made from the UFG material had higher tensile strength and yield stress than the bulk, while ductility was lower. Lower values of Young's modulus were observed during the tensile testing of small specimens made from UFG as well as bulk material. [ABSTRACT FROM AUTHOR]

Ni–P coated Si 3 N 4 reinforced Al6061 composites were fabricated by stir casting technique. Silicon nitride particles were varied in steps of 2 from 6 wt.% to 10 wt.%. Cast matrix alloy and developed composites were hot forged at a temperature of 500̊C using a 300T hydraulic hammer. Both as cast, hot forged matrix alloy and its composites were subjected to microstructural studies and fatigue strength tests. Microstructural studies reveal even distribution of silicon nitride particles with excellent bond between the matrix and reinforcement in both as cast and hot forged condition. It is observed that, increased content of reinforcement in both as cast and hot forged composites do result in significant improvement in fatigue strength. However, when compared with as cast matrix alloy and its composites, hot forged alloy and its composites exhibit higher fatigue strength. Both as cast and hot forged composites demonstrate improved fatigue strength when compared with the unreinforced alloys under identical test conditions. Fractured surfaces were examined using scanning electron microscopy (SEM) for the possible fracture mechanisms. [ABSTRACT FROM AUTHOR]

Al6061 and AZ31 plates were processed using accumulative roll bonding (ARB) method up to two passes to produce laminated composites. The sandwich stacks of Al6061/AZ31/Al6061 were held at 450 °C for 10 min in a cubical furnace and rolled together with reduction of 50% in one pass. The microstructural investigations were done using optical and scanning electron microscopes. The structures of the interface, mechanical and drop impact properties of the laminated composites after the first and second passes were investigated and compared with Al6061 and AZ31 alloy plates. It was found that Al6061 improved the elongation to failure property of AZ31 after the first pass of ARB process and the drop impact properties of AZ31 after the first and second passes. However, elongation to failure magnitude with the uniaxial tensile loading decreased with increase in the number of passes due to the formation of brittle intermetallic between the Al6061/AZ31 nonuniform interfaces. [ABSTRACT FROM PUBLISHER]