Aluminum Alloy Composites Research Articles

Phase composition of deformable D16 and B95 aluminium alloys with the quantitative assessment of overburning of different stages of development

This paper covers new overburning monitoring methods for D16 and V95 aluminum alloys based on use of a method of an energydispersive X-ray spectral analysis (EDS analysis). It is known that lowered performance of aluminum-based materials is often connected with overburning in their structure. Because the structural changes caused by overburning (flash-off of eutectics and excess low-melting phases and the subsequent crystallization of melted-off microvolumes) are followed by developing porosity, have negative impact on physical and chemical, mechanical and processing properties. The ability to reveal overburning at early stages allows to reject the defective metal. Characteristics sensitive to an early overburning stage are offered based on EDS analysis. A degree of the induced overburning in a D16 sheet is identified. B95 alloy structural components determining the alloy tendency to overburning are revealed. It is found that the EDS analysis makes it possible to reveal changes in the chemical composition of the structural elements of D16 and V95 aluminum alloys and identify an overburning stage quantitatively based on oxygen content. Overburning development leads not only to the higher content of oxygen in the chemical composition of aluminum alloys, but also lowers the electrical conductivity of the material. The paper considers a correlation relationship between the D16 alloy electrical conductivity with overburning induced in it, and oxygen content. The applicability of this method is caused by the method simplicity and a possibility to quantify the defect development in the heat-strengthened deformable aluminum alloys after process heatings. Also this method can be used as an additional research method when metallographic analysis gives no definite answer at identification of early overburning stages.

Effect of the aluminum alloy composition (Al-Cu-Li or Al-Mg-Li) on structure and mechanical properties of dissimilar laser welds with the Ti-Al-V alloy

This paper presents the results of the studies of dissimilar Ti-Al-V/Al-Cu-Li and Ti-Al-V/Al-Mg-Li laser welds. The main variable parameter was the laser offset towards the titanium alloy. It was found that strength properties of the welds were significantly affected by alloying elements (copper or magnesium) in the aluminum alloys. The presence of copper improved kinetics and thermodynamics of the welding process due to the formation of specific phases in the fusion zone. Also, it increased the strength of the dissimilar welds by 2.5 times compared with the Ti-Al-V/Al-Mg-Li joints.

Prediction of hardness of stir cast LM13 aluminum alloy ‐ copper coated short steel fiber reinforced composites using response surface methodology

AbstractCopper coated steel fibers reinforced LM13 aluminum alloy composites have been prepared using stir casting process. Experiments have been designed using response surface methodology (RSM) by varying wt % of reinforcement (0–10), stirrer speed (350 min−1–800 min−1) and pouring temperature (700 °C–800 °C). Microstructure and hardness of composites have been investigated. Analysis of variance, significance test and confirmation tests have been performed and regressions model has been developed to predict the hardness of composites. Response surface plots reveal that hardness of composites increases with increasing wt % of reinforcement and stirrer speed. The optimum stir cast process parameters for obtaining higher hardness are found to be the wt % of reinforcement of 8.2, pouring temperature of 748 °C and stirrer speed of 708 min−1.

Tensile and Compressive Behaviour of Hollow Glass Microspheres Reinforced LM13 Aluminum Alloy Based Syntactic Foam

Aluminium compound materials saw to be the best choice with its exceptional utmost of sketching out the material to give required properties. Aluminium alloy composites are expanding broad affirmation for aeronautics application in perspective on their high strength combined with low density. In the present work, an endeavour is made to prepare and focus the tensile and compressive behaviour of Hollow Glass Microspheres (HGM) reinforced Aluminium alloy LM13 based syntactic foam. Stir casting method was used to manufacture the aluminium alloy LM13 based syntactic foam with hollow glass microspheres (HGM) as space holders in 10 v%, 15 v% and 20 v% of concentration. Based on ASTM benchmarks, the composite samples were prepared. Results indicate that there is notable improvement in compressive strength while the tensile strength is on the lower side when observed in reference to the unreinforced LM13 alloy.

Experimental validity on the casting characteristics of stir cast aluminium composites

In the present work efforts are made to confirm the presence of actual weight percentage of reinforcements and its effect on aluminium alloy composites during stir casting technique. Two types of reinforcements, such as Silicon carbide and Boron carbide, were used by varying weight to manufacture Al6061 composites. The manufactured composites after stir casting show uniform distribution of hardness on the entire cross-section measured from top to bottom. The dissolved composites during the acid solubility test show approximately 95% of reinforcements present in the aluminium composites. Presence of reinforcements and quantity play a very important role to augment the properties of aluminium alloy by altering the microstructure during solidification and induces strain energy in the metallic matrix alloy. Almost 50–80% increase in hardness and 40–50% increase in tensile strength were observed in the as-cast composites as compared to aluminium alloy. Uniform distribution of reinforcements and hardness distribution on the entire cross-section clearly reveals that stir casting is an effective method for manufacturing aluminium composites.

Effect of B4C and graphite particulates on the mechanical and micro structural characteristics of AA 5052 hybrid composites

Reinforced aluminium metal matrix composites are being applied in various fields like automobile, aerospace and other industries. In this study the mechanical behavior of aluminium alloy (AA 5052) composites reinforced with boron carbide and graphite are studied. Aluminium matrix composite specimen was prepared by adding 2, 4, 6, and 8% of boron carbide and graphite by stir casting process. The composites were subjected to tensile, hardness and elongation studies. Scanning Electron Microscopy (SEM) was employed to analyze the uniform distribution of boron carbide and graphite of in the aluminium matrix metal. The microphotographs of the composites specimen exposed fairly uniform distribution of boron carbide and graphite particles in composites. Addition of B4C and graphite in aluminium matrix exhibited better mechanical properties and can be used as a possible material in marine, offshore and other industrial applications.

A comparative study of dry sliding wear behaviour of sillimanite and rutile reinforced LM27 aluminium alloy composites

The present work compares the dry sliding wear characteristics of sillimanite reinforced and rutile reinforced LM27 aluminium alloy based composites prepared by stir casting process. Particles in the size range of 1–32 μm were added in 5, 10, and 15 wt%. Microstructure, nanohardness, coefficient of friction, and wear rate characteristics were evaluated. Optical microscopy revealed uniform distribution of both sillimanite and rutile particles in the matrix. The hardness of sillimanite reinforced composites was higher than rutile reinforced composites. Further, the wear resistance of sillimanite reinforced composites was superior to rutile reinforced composites. However, coefficient of friction values of sillimanite particle reinforced composites were higher than the rutile particle reinforced composites. SEM-EDS analysis of wear track and wear debris revealed that abrasive wear and adhesion/delamination mechanisms were responsible for the wear of composites at low and high applied load conditions respectively.

Characterization, modeling and microstructure of composite aluminium alloy specimens after ECAP

The ECAP, the Equal Channel Angular processing or pressing, in general allows to modify the properties of materials at the microstructure level.In the proposed investigation, the composite specimens in aluminium alloy were subjected to different ECAP passes. The characterization after ECAP was performed by means of warm compression tests between 200 and 300°C with different ram velocities.By a coupled experiment-analytical methodology the friction effect was quantified and the stress-strain curves reported for different temperatures, deformation velocities and ECAP conditions. The friction effect was isolated and the flow behaviour trend of the alloy under different conditions modeled with two models. In particular a model in which the friction variable was considered and the other one in which the friction variable was completely neglected were built and tested. The countertrends in the initial ECAP passes were analyzed by microstructure investigation. The behaviour of the alloy under the considered conditions can be effectively modeled once identified the correct parameters in terms of pre-deformation.

Experimental investigation on stir and squeeze casted aluminum alloy composites reinforced with graphene

In the recent past aluminum alloy based metal matrix composites had played a major role in replacing most of the conventional materials. These composites are preferred due to its superior physical and mechanical properties. This research article is intended to compare the mechanical and microstructural properties of aluminum alloy based metal matrix composites manufactured through stir and squeeze casting processes. Metal matrix composite was fabricated using Aluminum alloy 7050 as the matrix and graphene as the reinforcement material. Composites were fabricated with 0.3, 0.5 and 0.7 weight percentage of graphene reinforcement through stir and squeeze casting processes. Microstructures observed on the samples showed uniform distribution of graphene as well as an excellent interfacial bonding with the aluminum matrix. Due to the addition of small quantity of graphene into aluminum alloy matrix, the mechanical properties were enhanced for the samples fabricated through both the processes. The strengthening mechanism of aluminum matrix with graphene addition is found to be favourable due to effective load transfer mechanism and grain refinement. Favorable results were obtained related to mechanical properties with the graphene content of 0.3 wt% through squeeze cast process, which also resulted in defect free castings.

Prior Solutionising Deformation Consequence on the Aging Characteristics of Steel Powder Reinforced Al 7075 Composites

Globally, in the application of structural materials, aluminum composites are emerging as pioneer materials due to balanced properties like ductility, strength, hardness and weight to volume ratio. It is obvious that addition of harder steel powder reinforcements to the softer aluminum alloy matrix will yield in larger benefits as energy efficient method, durability and recyclability for the composite. Infact, improvement in hardness levels at low temperatures in softer matrix aluminium alloys is the order of the day for wear related applications. Aluminum alloy composites especially Al 7075 matrix containing solid state soluble elements like copper, zinc and silicon with or without wetting agents like magnesium are heat treatable and got medium strength. The alloy matrix dispersed with solid reinforcements like carbides, oxides, flyash and steel powder contribute for the property improvement by tailoring the suitable heat treatment with flexibility in process parameters. Cold deformation assisted heat treatments, prior to or post solutionising challenge conventional heat treatments like age hardening or precipitation hardening. When the cold deformation is provided before solution treatment increases hardness by strain hardening with increased nucleation sites for phase transformation. When partial solutionising is given to the cold deformed composite retains the partial strain hardening effect on the specimen compared to complete solutionising. The retention of partial strain hardening followed by further aging develops complex interaction effect of strain hardening coupled with controlled precipitation of intermetallics on the composite for drastic uplift in hardness property. During conventional age hardening hardness and strength of the samples increase. Reduction in peak hardness value with increasing aging temperature is the renowned behaviour of age hardenable composites. The obtained peak hardness value is further increasing when cold deformation is supported with prior intentional deformation. Considering these features, it is proposed to perform prior solutionising deformation followed by subsequent aging on the stir cast Al 7075 –steel powder reinforced composite and analyse the microstructure and hardness distribution pattern by varying the steel powder quantity (0, 3 and 6 wt%), deformation density (10 and 20%) and aging temperatures (100 and 180oC)

Effect of SiC Particulate Reinforcement in A356 / LM25 Alloy Composites and in their Hybrids

LM25/A356 Aluminium Silicon alloy is characterized by high mechanical strength, corrosion resistance, machinabilty and excellent castability. Its prominent usage is found in high performance applications like in the automotive piston, cylinder blocks and heads, valve lifters, alloy wheels, brake pads and also in turbine blades. The prospects in applications of A356 are improved by heat treatment processes. Moreover the production of A356 Aluminium alloy composites renders provision for effectively tailoring the mechanical properties of the material by reinforcing the particulates of different ceramic materials at varying propositions. Although there are wide ranges of ceramic materials that could be potentially reinforced into A356 aluminium alloys, this paper exclusively reviews on SiC particulate reinforced A356 alloy composites and also its hybrid composites fabricated by strir casting method. This paper brings out the researches performed with A356/SiC composites under various experiment conditions to make this aluminium alloy available for other wide applications.

Phase Composition of D16 and V95 Deformable Aluminum Alloys with the Quantitative Assessment of Metal Burning at Various Stages of Development

New methods to monitor metal burning in D16 and V95 aluminum alloys based on using energy-dispersive X-ray spectral analysis (EDS analysis) are shown. It is known that the reduced properties of aluminum-based materials are often associated with the presence of metal burning in the structure. The structural changes caused by metal burning (partial melting of eutectics and excessive low-melting phases with the subsequent crystallization of molten microvolumes) are often accompanied by the development of porosity and negatively affect the physicochemical, mechanical, and manufacturing properties. The ability to reveal metal burning at early stages makes it possible to reject the defective metal. The characteristics sensitive to the early metal-burning stage are proposed based on the EDS analysis. The induced metal-burning degree in a sheet of the D16 alloy is identified. The structural components of the V95 alloy determining the alloy liability to metal burning are established. It is shown that the EDS analysis makes it possible to reveal the variations in the chemical composition of structural elements of the D16 and V95 aluminum alloys, as well as quantitatively identify the metal-burning stage by the oxygen content. The metal-burning development leads not only to an increase in the oxygen content in the chemical composition of aluminum alloys, but also to a decrease in the electrical conductivity of the material. The correlation between the electrical conductivity of the D16 alloy with induced metal burning and oxygen content is considered. The applicability of the EDS analysis is due to the simplicity of the procedure and the possibility of quantitatively evaluating the development of defects in heat-strengthened deformed aluminum alloys after manufacturing heating. It can be used as an additional method for investigation when metallographic analysis gives an ambiguous answer when revealing early metal-burning stages.

Microstructural Evolution and Strengthening Mechanism of SiC/Al Composites Fabricated by a Liquid-Pressing Process and Heat Treatment.

Aluminum alloy (Al7075) composites reinforced with a high volume fraction of silicon carbide (SiC) were produced by a liquid-pressing process. The characterization of their microstructure showed that SiC particles corresponding to a volume fraction greater than 60% were uniformly distributed in the composite, and Mg2Si precipitates were present at the interface between the matrix and the reinforcement. A superior compressive strength (1130 MPa) was obtained by an effective load transfer to the hard ceramic particles. After solution heat treatment and artificial aging, the Mg2Si precipitates decomposed from rod-shaped large particles to smaller spherical particles, which led to an increase of the compressive strength by more than 200 MPa. The strengthening mechanism is discussed on the basis of the observed microstructural evolution.

Machinability Research on the Micro-Milling for Graphene Nano-Flakes Reinforced Aluminum Alloy

In this paper, plain aluminum was chosen as matrix alloy and graphene reinforced aluminum alloy composites was successfully prepared via powder metallurgy approach. Micro-milling experiments were conducted to explore the effect of varying graphene nanoflakes (GNFs) content (0.5%, 1.0%, and 1.5% by weight) on the machinability of composites and their machining results were compared with that of plain aluminum. Chip morphology, milling force, and machined surface morphology were used as the machinability measures. Experiment results showed that when the content of GNFs is less than 1.5%, the grain refinement of GNFs plays a major role. The hardness and density of the composites are increased. When the content of GNFs is more than 1.5%, the agglomeration phenomenon is obvious, which reduces the hardness and density of the composites. Micro-milling results show that the milling force is the highest when the GNFs content is 1%, and curling degree of chips increased as FPT increase for a certain content of graphene of composites. Furthermore, when the content of GNFs in composites is more than 1%, the surface roughness of milling grooves is greatly improved, which may be related to the lubrication of graphene and the formation of continuous chips.

Preparation and Characterization of AA6061 Aluminum Alloy Composite Reinforced With Different Contents of Blast-Furnace Slag by Powder Metalurgy

ABSTRACTThe constant search for the improvement of the performance of materials of industrial application, evaluated under aspects of weight reduction, greater resistance, greater resistance to wear and better thermal stability, among others, associated with the search for the development of ecologically viable products, that convert the context of environmental degradation in preservation and sustainability, reflects the need to conduct research that results in new materials. The objective of this work is to obtain composites of the AA6061 aluminum alloy reinforced with different contents of coke coal blast-furnace slag by powder metallurgy. The processing of these materials was done by sieving, mixing and compacting powders of reinforced aluminum alloy with 5, 10 and 15% of blast-furnace slag. The cold uniaxial compaction was realized at a pressure of 500MPa. The obtained materials were sintered at 580°C for 3h under inert atmosphere. Unreinforced aluminum alloy samples were also produced. The characterization of the materials was realized by density and hardness measurements and three-point bending tests. The analysis of its microstructure was realized by scanning electron microscopy. As results, the composites presented a homogeneous distribution of the reinforcing particles and also a progressive improvement of the hardness and the bending strength with the increase of the slag content, producing an increase of 79% in hardness and 128% in flexural strength, when compared to the material without reinforcement obtained by the same process. Such results give the coke coal blast-furnace slag a new possibility of exploitation in the metal-mechanical sector, besides contributing with the environmental issue.

Effects of rolling on microstructures and properties of in-situ (TiB2 + ZrB2)/AlSi9Cu1 composites

In this paper, the (TiB2 + ZrB2)/AlSi9Cu1 composites were fabricated via in situ reaction from Al-K2TiF6-K2ZrF6-KBF4 reaction system. The effects of rolling on microstructures and properties of the composites were investigated by XRD, SEM, TEM and mechanical tensile test. In addition, the influence mechanisms of plastic deformation on aluminum alloy composites were discussed in detail. The results show that the in situ TiB2 and ZrB2 particle well distributed in the matrix with the size of 20∼50 nm and the morphology is short-stick or plate. The rolling technology could obviously optimize the microstructure, enhance the properties of the composite especially, after 6 passes hot rolling and 4 passes cold rolling, the TiB2 and ZrB2 particles clusters with size range from 80 to 150 nm were uniformly distributed in the matrix, the Si phases were fractured into different small parts with the size of less than 1 μm and the grains size were further reduced. The ultimate tensile strength (UTS) and elongation (EL) of in situ composite are 282 MPa, 17.6%, respectively. Also, the Portevin-Le Chatelier (PLC) phenomenon found in the composite was discussed.

Vibration Study on Aluminium Alloy 5083 Composite Reinforced with Montmorillonite

In this work, vibration behaviour of aluminium alloy 5083-reinforced nanoclay–montmorillonite nanocomposites was studied to have a better dynamic property for lightweight structural applications without affecting the mechanical property. Composite samples with various weight percentages of nanoclay were fabricated using stir casting method and achieved uniform dispersion with strong interfacial bonding between matrix and reinforcement. The influence of nanoclay in the aluminium alloy composite was also studied by different material characterization techniques such as scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction and microhardness test. From the study, it was concluded that the microhardness value of the aluminium alloy-reinforced nanoclay was decreased with the increase in nanoclay weight percentage. The mechanisms related to the shifting of frequencies were studied to know the effectiveness of reinforcement. The natural frequencies of the aluminium alloy 5083-reinforced nanoclay composites were found to be increased with the addition of 2 wt% of nanoclay in comparison with AA 5083 and 1 wt% of nanoclay.

Main Directions of Recent Works on Al-Zn-Based Alloys for Foundry Engineering

The composition and structural modification of high-aluminum zinc alloys and high-zinc aluminum alloys influence their wear properties and structural stability. The work described has been aimed at improving properties of the sand-cast Al-Zn-based foundry alloys, particularly their ductility and dimensional stability, by melt inoculation and/or change of chemical composition. In a series of studies, high-aluminum Zn-(25-26) wt.% Al-(1-2.5) wt.% Cu and high-zinc Al-(27-30) wt.% Zn-(1.5-2.5) wt.% Cu alloys have been doped with different levels of added Ti and Mn. The alloys’ structure and mechanical properties have been studied using scanning electron microscopy (SEM), light microscopy (LM), dilatometry and pin-on-disk wear measurements. A small addition of Ti introduced with Zn-4Ti master alloy leads to significant grain refinement of the high-aluminum zinc alloys. A small addition of Ti introduced with Al-3Ti-0.15C master alloy leads to significant grain refinement of the high-zinc aluminum alloys. In the ternary alloys, partially replacing Cu with Ti and/or Mn allows dimensional changes to be reduced while preserving good wear properties.

Optimisation of mechanical stir casting parameters for fabrication of carbon nanotubes–aluminium alloy composite through Taguchi method

The liquid metallurgical process route for synthesis of multiwalled carbon nanotube–A356 aluminium alloy (MWCNT-A356) composite is suitable for intricate designs and bulk production. In this work, MWCNT-CNT was fabricated through mechanical stir casting followed by thixoforming and modified by T6 (MT6) heat treatment. Hence, the optimisation and effect of variables such as amount of CNT, amount of wettability agent of Mg and mechanical stirring duration were investigated using a robust design of experiment (DOE), namely, Taguchi method, with two factorial levels. The signal-to-noise (S/N) ratio (‘larger is better’), hardness and ultimate tensile strength (UTS) were used as response variables. Results showed that the optimum hardness and UTS values of 106.4HV and 277.0MPa, respectively, were obtained from the nanoncomposite subjected to DOE run 4 and containing 0.5wt.% MWCNT, 0.5wt.% Mg and 10min of mechanical stirring. The hardness (76.3%) and UTS (108.4%) improved compared with those of the as-cast A356 alloy. The transformation of the microstructures and the porosity of the as-cast after thixoforming and MT6 modification were also discussed. This work demonstrated the optimised mechanical stir casting parameters for MWCNT-A356 fabrication and the enhanced mechanical properties achieved by thixoforming and heat treatment.

Investigation of T4 and T6 heat treatment on the wear properties of sillimanite reinforced LM30 aluminium alloy composites

In the present work, an attempt has been made to study the effects of heat treatment on the dry sliding wear properties of sillimanite reinforced LM30 aluminium matrix composites. Stir casting process was used for the processing of the composites. Composites with two different particle sizes (fine 1–20 µm and coarse 75–106 µm) and different weight ratio (3–15 wt% in the step size of 3 wt%) were fabricated. Further, the fabricated composites were subjected to the heat treatment as per T4 and T6 process. The composites were heated (at 540 °C), held at that temperature for 0.5–2 h and quenched in water. For T4, the composites were subjected to natural aging of 10–30 days at room temperature and for T6, composites were artificially aged by reheating to a temperature of 150–250 °C, holding there for 1–5 h, followed by air cooling. Hardness testing revealed that the composites subjected to T6 heat treatment exhibited superior hardness in comparison to normal composites and T4 heat treated composites. Further, wear analysis revealed that heat treatment of the composites affected the wear properties of the composites. Maximum improvement in the wear rate was observed for T6 heat treated composites. Also, the coefficient of friction of T6 heat treated composites was lower than other composites. Finally, SEM analysis revealed that the surface damage observed for T6 composites was lesser in comparison to other. In the initial period of wear abrasive wear was dominant and with increase in the sliding distance adhesive/delamination wear mechanism was dominant. Therefore, T6 composites revealed a superior combination of wear properties, and found to be in close comparison to grey cast iron used in the brake drum applications. Hence, 15 wt% reinforced T6 composites can be used as an alternate material for brake drum applications.