Uniform Dispersion Of Reinforcement Research Articles

Effect of B4C and CNTs’ nanoparticle reinforcement on the mechanical and corrosion properties in rolled Al 5083 friction stir welds

ABSTRACT Aluminium alloy 5083 plates were joined using friction stir welding (FSW) technique individually or in combination with boron carbide (B4C) and carbon nanotubes (CNTs). The effect of these reinforcements on mechanical properties, microstructure evolution and corrosion behaviour after FSW has been investigated. Radiography confirmed good fusion in the welded zone and the absence of surface or subsurface defects. The tensile testing results indicated a 35% decrease in tensile strength after FSW of the Al-5083 plates compared to the base metal, but it increased once again after the addition of individual reinforcements of B4C and CNTs due to grain refinement and second phase strengthening. In the sample with hybrid reinforcement, premature failure was observed due to lack of fusion and improper bonding between the two reinforcing materials. A similar trend was observed in the case of flexural testing. Severe plastic deformation and reduced grain size increased the micro-Vickers’ hardness values of reinforced samples. Evolution of the aluminium grain structure was analyzed using optical and stereo microscopy, while uniform dispersion of reinforcements and chemical composition was characterised by scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. Increase in corrosion resistance was also observed after FSW and addition of reinforcements.

Dry Sliding Wear Performance of Ni–SiC Composites Developed Through an In Situ Microwave Casting Process

Abstract Metal matrix composites of nickel-based powder reinforced with silicon carbide are processed through a domestic microwave applicator. In situ melting and casting of composites were carried out using microwave energy with average processing time of 25 min. Phase analysis of processed composites revealed the formation of some hard-intermetallic compounds such as nickel silicides (NiSi, Ni2Si, and Ni3Si2) and carbides (Cr3C2 and Cr7C3). Microstructure analysis confirms the favorable growth of equiaxed grains with uniform dispersion of reinforcement and low porosity defects (1.5–1.8%). The formation of hard-intermetallic compounds and the presence of SiC reinforcement led to the increased microhardness of composites. Sliding wear tests under dry sliding conditions with varying load and velocity conditions revealed the formation of stable oxide tribolayers at 1.0 m/s of sliding velocity and 15 N load. Fractography of worn-out samples revealed abrasion of surfaces at the lower load (10 N) condition. However, on increasing the load, the shearing of surfaces due to adhesion, plastic deformations, and surface pullout was observed. At higher loads (20 N) and higher sliding velocities (1.5 m/s), particle pullout and three-body abrasive wear mechanisms were observed. The overall weight loss study revealed that the addition of 5% and 10% volume fraction of SiC reinforcement reduced the wear-rate by 58.9% and 80.6% in comparison to the pure nickel casting at the sliding velocity of 1 m/s and under 15 N load.

Influence of TiO2 and MWCNT nanoparticles dispersion on microstructure and mechanical properties of Al6061 matrix hybrid nanocomposites

The influence of nanoparticle agglomeration plays a crucial role in altering the mechanical properties of the resulting nanocomposites. The pre-processing of nanoparticles prior to its addition in the matrix alleviates the agglomeration and helps to attain the uniform dispersion. In the present work, an ultrasonic-assisted stir/squeeze casting technique was employed to prepare the aluminum 6061 (Al6061) based hybrid nanocomposites reinforced with pre-processed TiO2 and multi-walled carbon nanotubes (MWCNTs). In order to achieve uniform dispersion of nano-reinforcements on resulting Al-based hybrid nanocomposites, four different reinforcements pre-processing routes, i.e. sonication, ball-milling, stirring and its combinations were adopted. The effects of numerous parameters such as reinforcement weight percentage, reinforcement pre-processing routes and fabrication techniques on the microstructure and mechanical properties of the hybrid nanocomposites were investigated. The effect of various pre-processing routes on the morphology evolution in MWCNTs and TiO2/MWCNT nanoparticles mixture were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. Further, the microstructural investigation of the prepared nanocomposites was carried out by employing optical microscopy (OM) and x-ray mapping analysis. Mechanical characterizations such as tensile strength and microhardness show significant enhancement in the mechanical properties of hybrid nanocomposites due to the addition of pre-processed nano-reinforcements. The ultimate tensile strength (UTS), yield strength (YS) and microhardness of the ultrasonic-assisted squeeze cast Al6061-TiO2 (1 wt%)-MWCNT (1.5 wt%) hybrid nanocomposite remarkably enhanced by 302%, 400% and 77 %, respectively, due to MWCNTs shortening, uniform dispersion of reinforcements and processing technique. The fractured surface morphology of hybrid nanocomposites was examined using Field Emission-SEM, which exhibits the presence of nano-reinforcements without any sign of destruction in their morphology.

Study on barium titanate and graphene reinforced PVDF matrix for 4D applications

This article reports the experimental investigations of polyvinylidene fluoride (PVDF) matrix-based composite feedstock filament (reinforced with barium titanate (BTO) and graphene (Gr) for possible 4-D printing applications) using fused deposition modeling (FDM). The mechanical, rheological, thermal, and morphological properties of in-house prepared FDM filament are also reported. The FDM feedstock filament was prepared with a twin-screw extruder (TSE). The process parameters of TSE for preparation of smart material-based filament with uniform dispersion of reinforcement (BTO and Gr) in the PVDF matrix have also been explored. Finally, the prepared filament has been used on FDM setup (without any change in hardware/software) for printing piezoelectric sensor with 4-D capabilities. The results of the study suggest that BTO and Gr have significant effect on the melt flow index of PVDF. The composite prepared with reinforcement of BTO and Gr shows a continuous flow, along with better thermal stability (based upon differential scanning calorimetry analysis), when 10–20 wt% BTO was added to the PVDF matrix. The observed maximum peak and break strength of the PVDF composite was 29.57 MPa and 26.50 MPa, respectively. The scanning electron microscopy and energy-dispersive X-ray analysis results reveal that the filament prepared with 20% BTO and extruded at 200°C with a screw speed of 40 r/min has better dispersion of reinforcement among the selected parametric settings. Finally, a piezoelectric response of 20 pC/N has been measured on the FDM-printed thermally stable sample suitable for 4-D applications.

An Overview of Key Challenges in the Fabrication of Metal Matrix Nanocomposites Reinforced by Graphene Nanoplatelets

This article provides an overview of research efforts with an emphasis on the fabrication of metal matrix nanocomposites (MMNCs) reinforced by graphene nanoplatelets (GNPs). Particular attention is devoted to finding the challenges in the production of MMNCs through the powder metallurgy techniques. The main technical challenges can be listed as: (I) reinforcement selection; (II) dispersion of reinforcement within the matrix; (III) reactivity between the reinforcement and matrix; (IV) interfacial bonding; (V) preferred orientation of reinforcement. It is found that some of these difficulties can be attributed to the nature of the materials involved, while the others are related to the preparation routes. It is reported that the challenges related to the process can often be addressed by changing the production process or by using post-processing techniques. More challenging issues instead are related to the composition of the matrix and reinforcement, their reactivity and the dispersion of reinforcement. These topics still bring significant challenges to the materials scientists, and it would be worth mentioning that the fabrication of MMNCs with a uniform dispersion of reinforcement, strong interfacial bonding, without detrimental reactions and improved isotropic properties is still a puzzling issue.

Hybrid aluminium matrix composites containing boron carbide and quasicrystals: manufacturing and characterisation

ABSTRACTHybrid composites of boron carbide (B4C) and Al62.5Cu25Fe12.5 quasicrystals (QCs) were prepared by ball milling and pressureless sintering in aluminium matrix to investigate their individual and hybrid effects on microstructural and mechanical properties. Hybrid composite contained B4C and QCs in 3 wt-% each, making a total of 6 wt-%. For reference, specimens of pure aluminium and two composites containing 6 wt-%B4C and 6 wt-% QCs were prepared. Microstructural characterisation was performed using optical, scanning electron microscopy and X-ray diffraction, while evaluation of mechanical properties was carried out by hardness and compression tests. Uniform dispersion of reinforcements in composites was observed along with significant increase in the mechanical properties. The composite containing 6 wt-% QCs demonstrated the highest hardness, while the hybrid composite showed better compressive properties.

Fabrication of polyethylene-based surface composite reinforced by carbon nano-tube and nano-clay through friction stir processing

In the present work, friction stir processing has been utilized to fabricate in situ polymer surface hybrid composite. The surface of polyethylene matrix was reinforced by the combination of multi wall carbon nano-tube and nano-clay powders. Here, L9 Taguchi orthogonal array was used to design the experiment taking into account the effects of tool rotary speed, travel speed, and reinforcement type on tensile strength flexural strength and modulus of electricity. The results showed that both tensile and flexural strengths varied in a similar manner by varying the process factors. Homogeneity in reinforcement, higher value of tool rotary speed (i.e. 1600 r/min), and low value of travel speed (i.e. 40 mm/min) cause appropriate material flow and uniform dispersion of reinforcement in friction stir processed zone. Also, it was shown that the middle value of tool rotary speed (1200 r/min) and travel speed (60 mm/min) along with applying pure nano-clay enhances the elasticity modulus.

Optimization of Stirring Parameters Using CFD Simulations for HAMCs Synthesis by Stir Casting Process

Hybrid aluminum matrix composites (HAMCs) are capable to meet recent demands of advanced engineering applications due to its tunable mechanical properties and lower cost. Stir casting is one of the prominent and economical method for processing of continuous reinforced HAMCs. In this method, flow pattern is the key factor for distribution of particles in the molten metal. Effective flow pattern can be achieved by optimizing stirring parameters i.e. blade angle, impeller size and stirring speed. However, complete study and optimization of flow is a challenge for research community. Finite element method simulation along with optimization technique is one of the effective combination to guide experimental research. In this paper, computational fluid dynamics has been used to simulate fluid flow during stir casting, whereas optimization of stirring parameters is done by Grey Taguchi method. Optimized parameters have been used for experimental synthesis of HAMCs. Furthermore, optical micrograph and hardness confirms about the uniform dispersion of reinforcements. These results may guide the researchers for the preparation of HAMCs with uniform particle distribution by stir casting route for industrial applications.

Microwave melting and processing of metal–ceramic composite castings

Applications of metal–ceramic composites are increasing in advanced materials field; however, efficient utilization of these materials depends on the cost involved in processing and structure–properties correlations. Processing of materials through microwave energy has already been accepted as a well-established route for many materials. In this work, composites of nickel-based metallic powder (matrix) and SiC powder (reinforcement) were successfully casted by microwave heating. The mechanism for the development of composite castings using microwaves is discussed with proper illustrations. The results of microstructure analysis of the developed cast revealed that uniform equiaxed grain growth with uniform dispersion of reinforcement. The results of X-ray diffraction analysis revealed that during microwave heating some metallurgical changes took place, which led to higher microhardness of cast. Micowave processed casting revealed lower defects (~1.75% porosity) and average Vickers microhardness of 920 ± 208 HV. This work reports the successful applications of microwaves in manufacturing, in the form of melting and casting of metallic powders.

Novel microwave composite casting process: Theory, feasibility and characterization

In the present work, the feasibility of high temperature melting and casting of metallic powders through microwave hybrid heating has been successfully attempted. The castings of nickel based powder reinforced with varying volume fraction of silicon carbide were successfully developed using microwave energy. The theory of microwave-metal interactions and the mechanism involved in the processing of composites through microwaves has been illustrated and discussed. The microstructure study of developed castings revealed uniform nearly equiaxed grain growth with uniform dispersion of reinforcements. Microwave heating allowed lower processing time and energy savings with the benefit of trifling pollution. The present work reports the successful applications of microwave processing towards cleaner manufacturing sector in the form of melting and casting of metallic powders.

Halloysite reinforced epoxy composites with improved mechanical properties

Abstract Halloysite nanotubes (HNTs) reinforced epoxy composites with improved mechanical properties were prepared. The prepared HNTs reinforced epoxy composites demonstrated improved mechanical properties especially the fracture toughness and flexural strength. The flexural modulus of nanocomposite with 6% mHNTs loading was 11.8% higher than that of neat epoxy resin. In addition, the nanocomposites showed improved dimensional stability. The prepared halloysite reinforced epoxy composites were characterized by thermal gravimetric analysis (TGA). The improved properties are attributed to the unique characteristics of HNTs, uniform dispersion of reinforcement and interfacial coupling.

Aluminium Metal Matrix Composite – An Insight into Solid State and Liquid State Processes

Aluminium metal matrix composites (AMMCs) are being considered as a group of superior material for its lightness, strength, high specific modulus, low coefficient of thermal expansion and good wear resistance properties. Solid state and liquid state processing methods are used to fabricate AMMCs. Achieving a uniform distribution of reinforcement within the matrix is one such challenge, which affects directly on the properties and quality of composite material. Powder metallurgy route, one of the solid state processing methods can be effectively used to get uniform dispersion of reinforcements with aluminium metal matrix. This paper presents the summary of the ball milling and stir casting processes to fabricate the AMMCs and its applications. Major issues like ball milling time, dispersion of reinforcements, grain size, the stirring time and speed are discussed. Also the effect of different reinforcement for AMMCs on the mechanical properties is discussed in detail.