Aluminium Based Composite Material

Friction stir welding (FSW) is the fastest evolving joining technology and the principal
prospective technique for implementing integral fuselage structure in aircraft manufacturing.
The viability of FS welds is dependent upon mechanical properties and production turnovers,
which are dependent on welding rates and tool design. This dissertation is about the multiobjective
characterisation of aeronautical alloys (AA5083-H111, AA6056-T4, AA6082-
H111) friction stir welded using the standard FSW tools, scrolled shoulder Triflat tool, and
the Bobbin tool respectively.
The effects of defects and microstructure on the mechanical behaviour of AA5083-H111
welds made from the standard tool were examined. SEM analysis showed that tunnel defects
resulted from partial consolidation at the root of the weld, and the microstructure of the weld
zones determined the failure mechanisms along the weld.
The effect of welding and rotational speeds on the integrity of AA6056-T4 FS welds
produced with scrolled shoulder Triflat tool was studied. Increased welding speeds and
advance per revolution led to improvements in mechanical properties and reduction in
residual stresses maxima. The retreating side TMAZ, which was the microhardness minimum
and tensile residual stress maximum, was also the failure location in most of the welds, hence
the microstructure and properties in this region were critical to the integrity of the weld. Bend
properties of the welds from the Triflat tool were good, because of the absence of root flaws.
The influence of two different tool designs (standard tool and standard Bobbin tool) on
mechanical behaviour and microstructure of AA6082-T6 was also studied. The standard tool
produced welds with better static properties than the bobbin tool, but most of the specimens
failed prematurely, and root bending resulted in cracks, because of alumina rich layers in the
weld nugget and root flaws. Bobbin tool welds had lower mechanical properties (70% weld
efficiency), the bend strength was better, with no flaws.
In the welds, the microstructure and microhardness which were influenced by the welding
rates which determined static properties, failure locations and residual stress minima and
maxima. The study also supported previous findings that the nature and distribution of
precipitates in the 6XXX series aluminium FS welds was important for determining
mechanical properties, unlike the 5083-H111 FS welds where the Hall-Petch effect was more
influential.

The paper provides an overview of tribological properties of nanocomposites with aluminium matrix. Nanocomposites represent a new generation of composite materials with better properties than conventional composite materials. The paper presents and explains the most common methods of nanocomposites production. In addition, the overview of tribological properties is presented through the equipment used for testing; amount, size and type of reinforcement; matrix material and manufacturing process; and test conditions. ARTICLE HISTORY Received 15 August 2016 Accepted 3 September 2016 Available online 30 September 2016

In situ composites are a class of composite materials in which the reinforcement is formed within the matrix by reaction during the processing. In situ method of composite synthesis has been widely followed by researchers because of several advantages over conventional stir casting such as fine particle size, clean interface, and good wettability of the reinforcement with the matrix and homogeneous distribution of the reinforcement compared to other processes. Besides this, in situ processing of composites by casting route is also economical and amenable for large scale production as compared to other methods such as powder metallurgy and spray forming. Commonly used reinforcements for Al and its alloys which can be produced in situ are Al2O3, AlN, TiB2, TiC, ZrB2, and Mg2Si. The aim of this paper is to review the current research and development in aluminum-based in situ composites by casting route.

Strict requirements that are put on mechanical constructions from the aspect of increase of exploitation periods and reduction of their weights, therefore of
their prices as well, implicate developments and applications of new composite materials with matrices of lightweight metals. Composite materials with
metal matrices are used for engine cylinders, pistons, disc and drum brakes, Cardan shafts and for other elements in automotive and aviation industry. The
most important type of metallic materials is composite materials with matrices of aluminium alloys due to a set of their beneficial properties. Improvement
of mechanical, especially tribological properties of hybrid composites were provided by the use of certain reinforce materials such as SiC, Al2O3 and
graphite in defined weight or volumetric share. New developed hybrid composites with aluminium matrices have significantly higher resistance to wear,
higher specific stiffness and higher resistance to fatigue. By the increase of quantities of produced elements made of hybrid composites, decrease of their
prices is induced that even further enlarge their applications. The applications of aluminium hybrid composites are considered from the aspect and with
the focus on automotive industry

In this study, the effect of Sc addition on the grain refinement, modification of the eutectic Si, mechanical and wear properties of A356 and A356–10 wt% TiB2 in situ composite has been investigated. The A356– 10 wt% TiB2 composites were prepared by an in situ reaction between K2TiF6 and KBF4 salts, which are added in proper stoichiometric ratio to form TiB2 in the A356 alloy melt at a temperature of 1073 K (800 C). Al–2 wt% Sc master alloy was added to A356 and A356–10 wt% TiB2 melt to introduce 0.2 and 0.4 wt% Sc in the alloy and the composite. Addition of Sc reduced the secondary dendrite arms spacing (SDAS) by 50% and changed the Si morphology from needle-like to fine spheroidal particles. Microstructure of Sc modified alloys which were cast for different holding times of 0, 30, 60 and 120 min indicated that there was no fading or poisoning effect on the SDAS and eutectic Si morphology. Hardness was found to increase due to addition of Sc and TiB2 Pin-on-disk wear tests indicated that Sc addition increase the wear resistance of A356 alloy but reduced the wear resistance of A356–TiB2 composite.

The influence of alumina volume percent and solution heat-treatment on the corrosion behaviour
of Al (6063) composites and its monolithic alloy in salt water, basic and acidic environments is
investigated. Al (6063) – Al2O3 particulate composites containing 6, 9, 15, and 18 volume
percent alumina were produced by adopting two step stir casting. Mass loss and corrosion rate
measurements were utilized as criteria for evaluating the corrosion behaviour of the composites.
It is observed that Al (6063) – Al2O3 composites exhibited excellent corrosion resistance in NaCl
medium than in the NaOH and H2SO4 media. The unreinforced alloy exhibited slightly superior
corrosion resistance than the composites in NaCl and NaOH media but the composites had
better corrosion resistance in H2SO4 medium. Furthermore, solution heat-treatment resulted in
improved corrosion resistance for both the composites and the unreinforced alloy while the
effect of volume percent alumina on corrosion resistance did not follow a consistent trend.

The viability of developing low cost – high performance Al matrix hybrid
composites with the use of bamboo leaf ash (an agro waste ash) and silicon
carbide as complementing reinforcements was investigated. Silicon carbide
(SiC)particulates added with 0, 2, 3, and 4 wt% bamboo leaf ash (BLA) were
utilized to prepare 10 wt% of the reinforcing phase with Al-Mg-Si alloy as
matrix using two-step stir casting method. Microstructural characterization,
mechanical properties evaluation and corrosion behaviour were used to
assess the performance of the composites. The results show that the
hardness, ultimate tensile strength, and percent elongation of the hybrid
composites decrease with increase in BLA content. The fracture toughness of
the hybrid composites were however superior to that of the single reinforced
Al - 10 wt% SiC composite. Only the 2 wt % BLA containing hybrid composite
had specific strength value comparable to that of the single reinforced
composite. In 5wt% NaCl solution, it was observed that the 2 and 3 wt %
BLA containing hybrid composites had higher corrosion resistance in
comparison to the single reinforced Al - 10 wt% SiC composite but the
reverse trend was observed in 0.3M H2SO4 solution where the single
reinforced had superior corrosion resistance.

Investigation of tribological behaviour of the hybrid composite, whose substrate is Al/Si alloy A356, reinforced with 10 wt. (%) of silicon carbide (SiC) and 0 and 5 wt. (%) of graphite (Gr) is presented in this paper by application of the Taguchi method. The composites are obtained by the compocasting procedure. The tribological investigations were realised on the tribometer with the block-on-disc contact pair in lubricating conditions and for the two values of the sliding speed, 0.25 and 1 m/s, two values of load 40 and 120 N and two values of the sliding path, 1200 and 2400 m. The wear traces were measured within the experiment, namely the wear intensities were calculated and results analysis was performed by application of the ANOVA technique. The strongest influence on the wear intensity was exhibited by the normal load (39.05%), then follow wt. (%) of the reinforcer (26.84%), the sliding speed (20.93%) and the sliding path (10.72%). The smallest wear appears in hybrid composite Al/SiC/Gr with 5 wt. (%) of the graphite reinforces, at the lowest load of 40 N, sliding speed of 1 m/s and along the sliding path of 2400 m. The main aim of their study is to provide new information and knowledge about the tribological behaviour of hybrid composites with a base of Al-Si alloy A356 reinforced with 10 wt. (%) SiC and with the addition of 0 and 5 wt.% Gr under lubricated sliding conditions.

In today's competitive world need has been increased towards development of low cost, efficient, lightweight, corrosion resistive, highly reflectivity, tough, conducive materials. Aluminium alloy composites are well known for its better thermal expansion coefficient, wear resistance, corrosion resistance and other mechanical properties. Composites are materials which are made up of two or more materials; when combined together it shares some properties of these combined elements. These combinations can be designed to have different properties like stiffness, resistance to impact or use in high temperature Environments. Nanocomposite is emerging as high strength advanced materials for the industrial applications that have potential of satisfying recent demands of advanced engineering applications. In this paper an attempt has been made to provide a brief review on aluminium and its alloy, aluminium matrix composites and nanocomposites, fabrication and characterization technology and to suggest a least expensive method for production of nanocomposites.

The paper presents tribological behaviour of hybrid aluminium composite A356/10SiC/3Gr in dry-sliding conditions. Hybrid
composites were made with a modified compocasting procedure and tribological tests were conducted on a tribometer with a
block-on-disc contact geometry. An analysis of the effects of three sliding speeds ((0.25, 0.5 and 1) m/s) and two normal loads (10 N and 20 N) on the wear volume and wear rate was conducted for different sliding distances. The total sliding distance was
300 m. SEM and an EDS analysis of the wear surfaces of the tested material were also performed. The analysis of the wear
surfaces shows an intensive adhesive wear of hybrid composites. Also, the appearance of mechanically mixed layers (MMLs) was confirmed, i.e., an increase in the concentration of iron in the hybrid composite material.

Tribological behaviour of a hybrid composite with the aluminium alloy base A356 reinforced by 10 wt. % SiC and 5 wt. % of graphite is treated in this paper. The optimization of tribological behaviour was conducted through the application of Taguchi method. Hybrid composites were obtained in the compocasting procedure. Tribological examinations were executed on the block on disc tribometer with the variation of two different load values (20 and 30 N), three sliding speed values (0.25, 0.5 and 1 m/s) and three sliding distance values (30, 90 and 150 m). All the examinations were carried out in conditions with no lubrication existing. The analysis of the wear rate was conducted using the ANOVA method of analysis. The greatest impact on the wear rate has the load (62.11 %), then the sliding speed (32.88 %), and the least the sliding distance (2.57 %). The interaction of the factors does not have a significant impact on the wear rate.

"For powder-based metal composite manufacturing, mechanical alloying has been widely used to disperse the clustered carbon nanotubes (CNTs) in the metal matrix. However, the effects of mechanical alloying time and CNT dispersion on the microstructure and mechanical properties of the metal–CNT composite have not been fully investigated. In this study, aluminum alloy 6061 (Al6061)–CNT composites were synthesized by semi-solid powder processing from powders that had been mechanically alloyed for different durations. The powder morphology, microstructure, hardness, flexural strength, fracture surface, and composition of the Al6061–CNT composites were analyzed. The results showed that the multi-walled CNT agglomerates were first crushed into thin layers and then dispersed during the mechanical alloying procedure. The CNTs on the surfaces of Al6061 particles at various mechanical alloying times showed that the CNT length decreased quickly to about 1.2 m after 1 h of mechanical alloying and below 1 m after 3 h from the original length of over 5 m. The grains of the Al6061–CNT composites deformed severely during the mechanical alloying process. The hardness improved as the mechanical alloying time
increased. However, the bend test and fracture surface indicated reduction of the composite ductility with increasing mechanical alloying time. Compositional analysis also showed formation of aluminum carbide (Al4C3) due to the CNT addition. In addition, a modified shear lag model was used to predict the strength of Al6061–CNT at different mechanical alloying times."

Nanosized aluminium oxides (NAOs) are an important class of minerals widely found in soil, sediment, aquifer, and aquatic environments. Over the decades, these minerals have been explored as sorbents for the removal of wastewater contaminated with metal ions, anions, organic dyes, humic substances, phenolic compounds, pesticides, and pharmaceuticals from contaminated wastewater. This review summarizes the reported research of NAOs as sorbents and provides details on their sorption capacities including maximum removal capacity under various experimental conditions. Information on the composition, synthesis, characterization and experimental parameters together with sorption mechanisms is provided. A compilation of such information is not currently available and so this review should enable workers in the area to make more informed choices on suitable sorbents for large-scale environmental samples and be able to develop more efficient processes for environmental pollutant clean-up.

The indentation hardness of Al-SiCp metal-matrix composites synthesized by stir casting process was investigated.
Stir casting method was selected as the casting method due to its simplicity, flexibility and applicability. This method allows a
conventional metal processing route to be used which minimizes the cost of the product. The silicon carbide particles to be
used were first ball milled for size reduction. These particles were then sieved in a mechanical shaker to obtain different
particle sizes. SiC particles of size 74μm corresponding to mesh 200 were selected for addition to the Al matrix. The
composite was prepared by adding preheated SiC particles to the Aluminium melt via stir casting. Test specimens were
prepared by varying the wt% of SiC (1%, 3%, 5%, 7% and 9%). As the SiCp additions were increased, the hardness of the
composite increased to a large extent. This can be attributed to the uniform distribution of the SiC particles in the Al matrix
via stir casting method.