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In this work Al-ZnO-Y2O3 hybrid composites were fabricated utilizing powder metallurgy and hybrid microwave sintering approach from the powder blend of Al, ZnO and Y2O3. Depth sensing nano-indentat...

In order to reduce oil consumption and avoid fossil fuel-related environmental problems, scientists are always looking for lightweight structural materials that show high performance during both pr...

Background Baveno VI criteria for screening varices needing treatment (VNT) have not yet been validated in an exclusive pediatric and adolescent set of the population, in whom baseline parameters differ in relation to adults. Therefore, our primary objective was to validate Baveno VI and its expanded form in children below 18 years of age. The secondary aim was to elicit whether any revision of the above criteria with a target of not missing more than 5% VNT could be more accurate for this age group. Materials and methods The work was carried out in two medical institutes, over a span of 3 years. Consecutively enrolled patients below 18 years of age, with compensated cirrhosis confirmed by liver biopsy, were evaluated for related blood parameters, transient elastography (TE) and esophagogastroduodenoscopy. Results Out of the 33 recruited patients, five (15.15%) met the criteria for VNT. The sensitivity, specificity, PPV and NPV of Baveno VI and Expanded Baveno VI were observed as 60%, 92.3%, 60% and 92.3%, and 20%, 100%, 100% and 88%, respectively. We found that the Revised Baveno VI criteria with TE 175×109 cells/L, with sensitivity 100%, specificity 79%, PPV 45%, NPV 100% and accuracy of 82%, are more appropriate for this age group. Conclusion We propose that further multicentrer studies with a larger sample size should be conducted before incorporating Revised Baveno VI criteria for high-risk varices in patients below 18 years in future guidelines.

In the present research, an attempt was made to determine the suitable coated tool for drilling AA5052 nano hybrid sandwich sheet using Response Surface Methodology (RSM) and Taguchi method. The wo...

Metastatic castration-resistant prostate cancer (mCRPC) is a natural sequela in advanced prostate cancer following resistance to standard treatment regimes, where patients develop with rising PSA, bone pains, and high disease volume. Further palliative treatment is the need of the hour for ensuring disease control and quality of life. In recent times, many novel methods have been evolved for these patients. Endo-radioligand therapy with Lutetium 177 prostate-specific membrane antigen 617 (Lu-177 PSMA) based on the Theranostic concept has emerged as a promising tool among these. We present here the current status of Lu177-PSMA for mCRPC patient and future directions.

Graphene and its derivatives, due to their extraordinary mechanical, thermal, and tribological properties, are extensively used to fabricate bulk graphene-based nanocomposites. On the other hand, m...

This study examined the effect of AISI H13 steel-tapered tool on the dissimilar friction stir welding of 7075-T651 and 1200-H19 aluminium alloys. Three mechanical tests which include hardness, tensile strength and impact energy were conducted to study the effect of tilt angle, rotational and welding speeds on the weld integrities, 50 and 175 HV were respectively obtained as hardness values for AA1200- H19 and AA 7075- T651, the hardness values were measured for three selected welding speeds of 30, 60 and 90 mm/min representing low, medium and high at a constant rotational speed of 1500 rpm, a tool tilt angle of 2°.The hardness increases with the welding speed from 81.99 to 98.5 HV as the speed increased from 30 to 60 mm/min and dropped to 77 HV at 90 mm/min.The impact energy increased from 12.9 to 21.4 J with an increase in the welding speed from 30 to 60 mm/min and dropped to 5.4 J at 90 mm/min.The ultimate tensile strength (UTS) increased from 126.04 to 151.54 MPa with an increase in the welding speed from 30–60 mm/min and decreased from 151.54 to 128.37 MPa, the hardness at 1500 rpm and 60 mm/min increased from 70.22 to 98.58 HV with an increase in the tilt angle from 1- $${2^^\circ }$$, a further increase from 2–3 o reduced the hardness from 98.58 to 66 HV, UTS increased from 123.32 to 151.54 MPa as tilt angle increased from 1–2 ° and decreased to 122.2 MPa, the medium tilt angle of $${2^^\circ }$$,rotational and traverse speeds of 1500 rpm and 60 mm/min respectively gave the highest impact energy of 21.4 J.

This work examines the micrometer-scale wear behavior of pure Mg and its composites at various loads (100–500 mN) under single and multiple scratch conditions. The Mg-0.4Ce alloy reinforced with na...

The present study addresses the synthesis and characterization of polymethyl methacrylate (PMMA)/graphene oxide (GO) and PMMA/GO + TiO2 nanocomposites for potential application as dental materials....

Bulk Mg–3%Al alloy-based nanocomposites containing graphene nano-platelets (GNPs) were synthesised using the powder metallurgy technique incorporating energy efficient hybrid microwave sint...

The development of new polymer-based conductive adhesives with specific performances and improved conductivity are increasingly critical for thermally interface material (TIM). Epoxy resins have been widely used as a common interface material for conductive adhesives due to its well-known ability to accept wide range of fillers possibly derived from carbon, metallic or ceramic sources. These conductive fillers with high inherent thermal conductivity, together with a possibility to characterize and manipulate the system, leads to the production of thermally conductive adhesives with higher knowledge content for a number of electronics applications.

In the present study, magnesium composites containing pre-milled metastable Al90Y10 particles were synthesised using powder metallurgy route incorporating microwave-assisted sintering and hot extrusion. The results of X-ray diffraction reveal that the pre-milled powder changed from crystalline structure to metastable structure after 200 hours ball milling and the particle retained its metastable state in all composite samples. Microstructural characterisation shows that metastable particles were fairly distributed in the magnesium matrix and located along the grain boundaries. Further, when the amount of metastable particles increased, microhardness, 0.2%yield compressive strength and ultimate compressive strength increased significantly, coefficient of thermal expansion reduced gradually, while the compressive total strain remained almost the same. Work of fracture that indicates damage tolerance increased up to 66%. The interrelationship between microstructure and properties is discussed. Results sugges...

This study reports for the first time the synthesis of syntactic composite foams based on magnesium matrix and hollow fly ash cenosphere particles using the powder metallurgy technique involving hybrid microwave sintering. The effects of varying amounts of hollow cenosphere particle addition on the density, microstructure, thermomechanical and mechanical properties of pure magnesium were investigated. Density measurements indicated up to 18% reduction in density with the highest quantity of cenospheres (15%) addition to the magnesium. Microstructural examination demonstrated evenly distributed, intact and a few broken cenosphere particles with good interfacial integrity. Phase analysis showed finely distributed intermetallic phases such as MgO and Mg2Si due to the reaction between Mg matrix and the hollow cenosphere reinforcement. Mechanical property measurements showed retention/slight improvement in specific mechanical properties of magnesium due to hollow fly ash cenosphere particles. However, the tens...

Significantly light weight magnesium composite foams are synthesised by addition of fly ash cenosphere particles (waste from coal-fired power plants) in biocompatible pure magnesium using solidification-based disintegrated melt deposition technique. The density of the composite foams synthesised in this study approaches that of plastics- and polymer-based composites. Microstructure development of Mg/cenosphere composite foams was favourable as they exhibited better dimensional stability (reduced coefficient of thermal expansion) and remarkable improvements in tensile strengths, compressive strengths, compressive total strain and microhardness. The present study highlights the processing, microstructure and mechanical properties of Mg/cenosphere composite foams which hold great potential as light weight metal-based green materials for diverse weight critical applications spanning from engineering to biomedical sector.

Hybrid nano reinforcement particles with increasing volume percentage of copper have significantly enhanced tensile properties of commercially pure magnesium when incorporated using blend-press-microwave sintering powder metallurgy process. Incorporated hybrid reinforcement maintained their strengthening effect on magnesium matrix up to the temperature limit used in this study although gradually declined with increasing test temperature. Reinforcement particle assisted dynamic recrystallisation and thermally activated deformation process induced near super plasticity in commercially pure magnesium matrix at incomparably lower temperature and suggested the potential of near net shape fabrication in to intricate shape. Limit in total volume fraction of nanometre size reinforcement resulted the hybrid nano reinforcement with 0.3 vol.-% of metal particle most effective to enhance tensile characteristics of commercially pure magnesium.

Magnesium (with density, ρ = 1.74 g cc− 1) being ∼35% lighter than aluminium and ∼75% lighter than steel is an attractive and a viable candidate for the fabrication of lightweight structures. Being the designers' choice for weight critical applications, extensive research efforts are underway into the development of magnesium metal matrix composites (Mg-MMCs) through various cost effective fabrication technologies. In recent years, there has been a progressive advancement in utilising the microwave energy to consolidate powder materials, and the present study accentuates the use of energy efficient and environment friendly microwave sintering process to synthesise magnesium based composite materials. The processing advantages of the innovative and cost effective microwave assisted bidirectional rapid sintering technique followed by hot extrusion are first briefly introduced. Subsequently, the properties of various Mg-MMCs containing nanosized ceramic/metal particles, synthesised using this techniq...

A processing map for extruded AZ31-1Ca-1.5NAl composite has been developed, which exhibited four important domains for hot working. The corresponding temperatures and strain rates associated with these domains are: (1) 250–350°C and 0.0003–0.01 s−1; (1A) 350–410°C and 0.0003–0.01 s−1; (2): 410–490°C and 0.002–0.2 s−1; and (3) 325–410°C and 0.6 s−1 to 10 s−1. Dynamic recrystallization (DRX) occurred in all the four domains although different slip mechanisms and recovery processes are involved. Basal slip and prismatic slip dominates deformation in Domains 1 and 1A, respectively, with recovery occurring by climb that is lattice self-diffusion controlled. However, because of the high strain rates in Domain 3, recovery occurs through a climb process, controlled by grain boundary self-diffusion. The recovery mechanism in Domain 2 is cross-slip assisted by pyramidal slip along with basal and prismatic slip. The grain size has a linear relation with Zener–Hollomon parameter in all the domains. At high strain rat...

In this study, nano-AlN particles were introduced into pure Mg matrix through the powder metallurgy technique incorporating microwave assisted two-directional sintering followed by hot extrusion. The effect of varying volume fraction of nano-AlN addition on the microstructural and mechanical properties of pure Mg was investigated. Microstructural characterisation revealed marginal grain refinement due to the fairly uniform distribution of AlN nano-particulates. X-ray diffraction results indicated basal texture weakening in Mg/0·2AlN composite. Tensile property measurements revealed an overall increase in strength properties and ductility. Among the developed composites, Mg/0·8AlN displayed superior strength (∼30% improvement) and Mg/0·2AlN showed enhanced ductility (∼80% enhancement). Under compressive loading, the developed Mg/AlN nanocomposite formulations exhibited improved strength properties without significant effect on compressibility.

In the present study, the mechanical properties of magnesium composites containing nano-ZnO particles are investigated. An increase in microhardness was observed with increasing amount of ZnO from 0·5 to 1·5 vol.-% in magnesium. The tensile and compressive yield strengths of the composites remained similar to that of Mg. This is attributed to the heterogeneous grain size distribution and the resultant weak basal texture. The tension–compression yield asymmetry was also found to be minimal due to the lack of strong basal texture. The composites showed improved ultimate tensile and compressive strengths, and this is attributed to well known strengthening mechanisms due to the presence of fine reinforcement particles. The tensile failure strain was significantly improved in composites, while there was a compromise in compressive failure strain. The improved tensile failure strain was due to non-basal slip activation through grain refinement and lack of intense basal intensity in composites.

The tribological behavior of magnesium metal matrix composites lubricated with graphite nanoparticles as additives in paraffin oil was investigated using a pin-on-disc wear tester. The results of nano-graphite-lubricated conditions are compared with the results of the tribotests carried out with micro-graphite additives in paraffin oil, pure paraffin oil, and dry sliding conditions. Wear tests were conducted at loads ranging from 15 to 60 N and sliding speeds varying from 1.25 to 3.15 m/s for a constant sliding distance of 1,600 m. The worn surfaces of the composites were analyzed through scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX) spectroscopy. Characterization of the tribolayer and subsurface deformation layer of worn-out composites was accomplished using a novel focused ion beam (FIB) milling technique. The wear resistance of the metal matrix composite was observed to decrease with increasing severity of testing conditions (i.e., applied load and sliding speed) when tested und...

In the present study, magnesium based composites containing 1·1 vol.% of alumina particulates at nanolength scale were synthesised using disintegrated melt deposition technique. The main focus was to vary interaction time between molten magnesium and nano-Al2O3 particulates during stirring and to study its effects on the microstructure and mechanical properties. With an increase in stirring time, microstructural characterisation of the composite materials revealed reasonably uniform distribution of Al2O3 reinforcement, marginal grain refinement and presence of minimal porosity. Mechanical properties characterisation revealed that an increase in stirring time led to a simultaneous increase in hardness, 0·2% yield strength and ultimate tensile strength while ductility was compromised beyond 7·5 min stirring when compared to pure Mg. The optimal stirring time is observed to be in 5–7·5 min range in order to realise the best combination of strength, hardness, ductility and work of fracture.

In the present study, Mg based composite containing Al particles was fabricated by blending the Al particles in the Mg powder, followed by hot compaction, two directional microwave sintering and hot extrusion. Microstructural characterisation of the as extruded composite samples revealed a fairly uniform distribution of aluminium with some minor clustering and minimal porosity in the composite. X-ray diffraction results indicate the presence of Al2Mg3 intermetallics at the interface between Mg and Al. Mechanical properties characterisation revealed that the addition of Al particles resulted in an increase in macrohardness, interfacial microhardness, 0·2% yield strength and ultimate tensile strength (both in compression and tension). However, the ductility of the composite was found to be decreased by the addition of Al particles in the Mg matrix. The fractured samples after tensile testing showed a brittle mode of fracture with cleavage steps; however, the fractured sample after compression test s...

In the present study, an attempt has been made to tailor the properties of monolithic magnesium by initially reinforcing it with a predetermined amount of nanosize yttria particulates followed by hybridising it with nanocopper particulates in two different volume percentages of 0·3 and 0·6 vol.-% respectively. Both the monolithic magnesium and magnesium nanocomposites were synthesised using the blend press sinter powder metallurgy technique followed by hot extrusion. For sintering of the materials, an innovative hybrid microwave sintering method was chosen with the objective of realising savings in both time and energy. Test results revealed that both strength and ductility of pure magnesium increased with the addition of yttria and a hybrid reinforcement mixture of yttria and copper nanoparticulates. The best combination of properties in uniaxial tension was obtained for the Mg/(0·7Y2O3+0·3Cu) hybrid nanocomposite. The observed improvement in properties is attributed to synergistic influences of ...

In the present study, copper at the nanometer length scale is integrated with Sn–3·5Ag using the technique of powder metallurgy incorporating energy efficient microwave sintering. Superior mechanical characteristics were realised for the formulations containing nanometer length scale copper in excess of 1 vol.-%. Sn–3·5Ag reinforced with 2·5 vol.% nanosize copper particulates exhibited the best overall mechanical characteristics. Particular emphasis is placed on studying the effect of the increasing presence of nanosize copper particulates on the microstructure and property evolution of the Sn–3·5Ag matrix.

In the present study, sintering response of pure tin is assessed and correlated with microstructure and tensile behaviour following extrusion. This study was undertaken as there is no information in public domain on tin which is emerging as an interconnect material in its nearly pure forms. Benchmarking was carried out with unsintered tin as the recrystallisation temperature of tin is much lower than ambient temperature. Results revealed that energy efficient microwave sintered samples exhibit superior combination of microstructure and tensile properties when compared to unsintered and conventionally sintered samples.

The effect of chloride ions on passivation of pure Mg, Mg–0·6 vol.-%Mo composite, Mg–0·6 vol.-%Cu composite and Mg alloy AZ91D has been studied in 0·1M NaOH solution by cyclic polarisation and electrochemical impedance spectroscopy (EIS). An addition of even 0·05M of chloride ions was sufficient to cause breakdown of passivity. Cyclic polarisation curves revealed a positive hysteresis loop in the presence of chloride ions. Breakdown potentials decreased continuously, for all materials, with increasing addition of chloride. Electrochemical impedance spectroscopy studies revealed that the film resistance of all Mg based materials continuously decreased with the addition of chloride ions. The film resistance of Mg–0·6%Cu and Mg–0·6%Mo composites was lower than that of pure Mg and AZ91D. Mg–0·6%Mo composite showed the lowest film resistance in all the solutions. The increase in film capacitance, for pure Mg and Mg based composites, with the addition of chloride ions, was attributed to surface rougheni...

In the present study, the influence of multiwalled carbon nanotubes (CNTs) on the creep performance of 95·8Sn–3·5Ag–0·7Cu lead free solder is investigated. Composite solders containing varying weight percentages of CNTs were synthesised. Solder joints were fabricated and subjected to a series of tests under testing temperatures ranging from 25 to 125°C and applied stresses ranging from 4 to 18 MPa. Creep results revealed that solders containing CNTs exhibited significantly improved creep resistance and also creep time to failure increased. Stress exponents of composite solders were higher than that of monolithic solder. In general, stress exponent was found to increase with increasing applied stress and with decreasing testing temperature. The range of activation energies of composite solder with 0·01 wt-%CNT addition was found to be comparable to that of monolithic Sn–Ag–Cu. However, as the amount of CNT increased to 0·04 wt-%, the range of activation energies increased accordingly.

In the present study, magnesium composites with three different volume fractions of interconnected reinforcement (1·77, 2·65 and 3·85%) were successfully synthesised by using disintegrated melt deposition technique followed by hot extrusion. Microstructural characterisation revealed the absence of macro pores, minimal porosity and good reinforcement–matrix interfacial integrity. Thermomechanical analysis of the composites showed that the use of interconnected wire preforms as reinforcement marginally decreased the average coefficient of thermal expansion of the magnesium matrix. The mechanical characterisation of the composites revealed that the rule of mixture stiffness was closely realised in all the composite materials. The hardness and yield strength increased while the ultimate tensile strength and the ductility of the composite materials were adversely affected. The fracture surface revealed brittle mode of fracture for the matrix and ductile mode of fracture for the iron wire.

Nano-ZrO2 particulates containing magnesium nanocomposites were synthesised using blend press sinter hot extrusion technique. Microstructural characterisation showed reasonably uniform distribution of reinforcement, significant grain refinement of magnesium matrix, and the presence of minimal porosity. Mechanical testing revealed that the presence of nano-ZrO2 reinforcement leads to improvement in microhardness and 0·2% yield strength, and significant increase in ductility and work of fracture of magnesium matrix. Fracture surface of Mg matrix exhibited mixed mode (brittle ductile) fracture in the cases of Mg–ZrO2 nanocomposites.

Extruded composite propellant (ECP) is an entirely new thrust area in the development of composite propellants within India. These are based on high-density thermoplastic elastomers as a propellant binder with ammonium perchlorate (AP) as an oxidizer and aluminum (Al) as a metallic fuel. Thus, this class of propellant not only provides higher energy but also yields higher density impulse. There are no pot life problems as with conventional slurry cast composite propellants because the binder used is thermoplastic in nature and hence can be recycled. ECP can take up solid loadings up to 90% and have very good dimensional stability. The present article reports evaluation of a thermoplastic polyurethane, viz. Irostic, as a binder for extruded composite propellants. The polymer was characterized completely before use. The feasibility of propellant processing has been studied and processing parameters have been established. Around 50 propellant formulations are processed for selection and optimization of plast...

In the present study, magnesium composites reinforced with different volume fraction of submicron size Al2O3 particulates were synthesised using powder metallurgy technique incorporating an innovative microwave assisted rapid sintering technique. The sintered materials were subsequently hot extruded for characterisation in terms of microstructural, physical and mechanical properties. Microstructural characterisation results revealed a reasonably uniform distribution of Al2O3 particulates, minimal porosity and good matrix reinforcement interfacial integrity. The average coefficient of thermal expansion (CTE) value for Mg–Al2O3 composites was found to decrease with increasing amount of submicron Al2O3 particulates. Mechanical characterisation of the composites revealed an increase in hardness, elastic modulus, 0·2% YS and ultimate tensile strength (UTS) with the increase in amount of alumina particulates. Ductility exhibited the reverse trend. An attempt is made in the present study to correlate the...

In the present study, elemental and nanoAl2O3 particulate reinforced magnesium materials were synthesised using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterisation of the composite samples showed retention and uniform distribution of reinforcement, grain refinement of magnesium matrix, and the presence of minimal porosity. Physical properties characterisation revealed that the addition of nanoAl2O3 particulates as reinforcement improves the dimensional stability of pure magnesium. Mechanical properties characterisation revealed that the presence of nanoAl2O3 reinforcement led to significant improvement in hardness, elastic modulus, 0·2% yield strength, UTS and ductility. The results further revealed that the combination of 0·2% yield strength, UTS, and ductility exhibited by nanoAl2O3 reinforced magnesium remained much superior even when compared to magnesium reinforced with a much higher volume percentage of micrometre size SiCp. An at...

The objective of the present work was to investigate the effect of presence of SiC reinforcement and the vibration frequency on the overall damping characteristics of pure magnesium. The testing method uses a combination of the modified free – free beam method coupled with a circle fit approach. The effect of frequency on the damping property was studied by adding end masses to the specimen so as to alter the resonant frequency of the suspended beam. In the present study, the results are compared against a monolithic magnesium sample. The results revealed a higher damping capability of the composite specimen at all tested frequencies when compared to monolithic magnesium. Both monolithic and reinforced magnesium showed a progressive decrease in damping with an increase in frequency. An attempt is made to rationalise the damping behaviour of the composite in terms of the presence of a process induced plastic zone at the matrix/particulate interface and the operating frequency.

In the present study, three aluminium based functionally gradient materials (FGMs), reinforced with different ceramic particulates (silicon carbide, aluminium oxide, and titanium carbide), were successfully synthesised using the innovative gradient slurry disintegration and deposition (GSDD) technique. The results for Al/SiC and Al/Al2O3 revealed, in common, an increase in the weight percentage of reinforcement along the direction of deposition, to result in an increase in porosity and microhardness. However, for Al/TiC, the reverse trend was observed, with porosity and microhardness decreasing with increasing distance from the base of the ingot. The porosity levels for Al/TiC were also found to be significantly lower than those ofthe other two FGMs. Thermomechanical analysis of the FGMs showed thatthe average coefficient of thermal expansion of the high reinforcement end was reduced, as compared to the high aluminium end. Sliding wear test results also revealed that the high reinforcement end wa...

In the present study, elemental Cu powder was mechanically milled to reduce the grain (crystalline) size to the nanorange (< 100 nm). The powder was consolidated by die cold compaction. Omitting the sintering process, the powder compacts of 10 h mechanically milled powder and elemental powder without mechanical milling (0 h mechanically milled) were hot extruded at different temperatures to maintain a crystallite size within the nanoregime. Characterisation revealed that samples with relatively lower grain size (63 nm/10 h mechanically milled) exhibited reduced density and ductility, similar dimensional stability, and significantly enhanced hardness, 0.2% yield strength, and ultimate tensile strength. Particular emphasis was placed on correlating the properties of the samples with their microstructural features.

In the present study, a magnesium based composite with about 11.5 wt-%SiC particulates was synthesised using an innovative disintegrated melt deposition technique followed by extrusion at different temperatures of 350°C, 250°C, 150°C and 100°C. Microstructural characterisation of the extruded samples showed an increase in alignment of SiC particulates in the direction of extrusion, reduction in number of SiC particulate clusters and improved distribution of the SiC particulates as the extrusion temperature decreased. Good interfacial integrity and minimal porosity was also observed for all the samples. Mechanical properties characterisation revealed that a decrease in extrusion temperature from 350°C to 100°C led to a significant increase in hardness, elastic modulus, 0.2% yield strength while the average UTS and ductility remain unaffected. Subsequently, isothermal heat treatment at 100°C with holding times of 5 and 10 h were also carried out for samples that were extruded at 100°C. The results o...

The requirements for reduced fuel consumption and limited emission have triggered high consumption of magnesium in recent years due to its inherently low density and ensuing potential to exhibit advantageous specific mechanical properties. In the present study, monolithic and copper particulate reinforced magnesium composites were synthesised using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterisation of the composite samples showed uniform distribution of Cu and Mg- Cu based intermetallic particulates in the matrix material, good interfacial integrity of the magnesium matrix with reinforcement particulates, and the presence of minimal porosity. Physical properties characterisation revealed that the addition of copper as reinforcement marginally reduced the coefficient of thermal expansion (CTE) of pure magnesium. Mechanical properties characterisation revealed that the addition of copper in magnesium led to significant improvement in ha...

In this article, the synthesis of a newer generation of metastable aluminum- titanium (Al-Ti) materials is presented and discussed. Two equilibrium processing methods, using disintegrated melt deposition, were chosen and tried. The first restricted the interaction time between powders of titanium and molten aluminum, whereas the second essentially involved a change in surface characteristics of titanium powders prior to their addition to molten aluminum. The results of microstructural characterization and X-ray diffraction studies conducted on the Al-Ti materials, synthesized using the two methods, reveal the presence of elemental titanium and other phases in the aluminum matrix, thereby providing confirmation as to the metastable nature of these materials. Results also indicate that a significantly higher amount of titanium can be retained in the metal matrix at low processing temperatures when compared with predictions of the equilibrium Al-Ti phase diagram. Results of this study provide an inn...

In this study, an aluminium alloy, AA 1050, was reinforced with an interconnected, axisymmetrical, galvanised iron wire preform. The composite was synthesised using a conventional casting technique followed by hot extrusion. The composite was tested in a free - free type suspended beam arrangement, coupled with circle fit approach to determine damping characteristics. This testing method is based on classical vibration theory, by which the geometry and material properties of the metal matrix composites are related to the resonant frequency and structural damping of the test specimen. Using the fact that the ratio of the vibration response to the applied force fits to a circle in the Argand plane for each resonant frequency of the test specimen, the damping factor and natural frequency is predicted accurately for the test specimen. To demonstrate the accuracy of the test method, test results of a pure aluminium sample are compared against results from other test methods from published literature. ...

(2002). Characterization And Analysis Of Energy Dissipation By Metal Based Composites. Materials Technology: Vol. 17, No. 4, pp. 231-234.

In the present study, Al/SiC based functionally gradient materials (FGMs) were successfully synthesised using the gradient slurry disintegration and deposition technique. Gradients of SiC for the starting weight of 18% were successfully established by varying the stirring speed of the molten melt. The results revealed, in general, increases in the weight percentage and clustering tendency of SiC, porosity, and microhardness and a reduction in grain size, with increasing distance from the base of the FGM ingots. The results also showed that an increase in the stirring speed increases the homogeneity of SiC particulates distribution, thus resulting in a decrease in the gradient of reinforcement along the deposition direction. Furthermore, an increase in the stirring speed decreases the number of clusters formed per unit area. An attempt has been made in the present work to establish the trend between processing parameters, such as stirring speed and the gradient of SiC particulates realised in the i...

This study has addressed the feasibility of synthesising and recycling a silicon carbide reinforced magnesium composite using an innovative disintegrated melt deposition technique with the aim of improving the mechanical properties. Microstructural characterisation studies revealed a marginal decrease in porosity and reinforcement content, and no change in grain morphology, reinforcement distribution pattern, and interfacial integrity between matrix and reinforcement following recycling. Results of physical and mechanical property characterisation revealed increases in 0.2% yield strength, ultimate tensile strength, ductility, and coefficient of thermal expansion of the recycled specimens when compared with the parent composite. These properties have been rationalised in terms of the microstructural characteristics associated with the disintegrated melt deposited composite specimens. Particular emphasis was placed on studying the effect of recycling on the microstructure and properties of the comp...

In the present study, a galvanised iron wire mesh structure of two different types was used to reinforce aluminium alloy 1050. The composite was synthesised using conventional casting followed by hot extrusion. Microstructural characterisation of the composite specimens showed good interfacial integrity between the matrix and the reinforcement wire. Thermomechanical analysis demonstrated that the average coefficient of thermal expansion of the composites was decreased below the values predicted by theoretical models. Tensile tests conducted on the composite specimens revealed that the average elastic modulus of the composites exceeded the rule of mixtures predictions. The average values of 0.2 yield strength and ultimate tensile strength of the composites were found to be higher than those of the monolithic aluminium alloy irrespective of a low volume fraction 0.049 of reinforcement. This unusual variation in the properties clearly reflects the uniqueness of using interconnected wires as reinforce...

In the present study, elemental magnesium and magnesium–silicon carbide composites were synthesised using the methodology of fluxless casting followed by hot extrusion. Microstructural characterisation studies revealed low porosity and a completely recrystallised matrix in every material. The average size of the recrystallised grains was found to decrease with an increasing presence of SiC particulates. For the reinforced magnesium, fairly uniform distribution of SiC particulates and good SiC–Mg interfacial integrity was realised. The results of X-ray diffraction studies indicated the absence of oxide phases and no evidence of interfacial reaction products except in the case of Mg–26.0 wt-%SiC sample. Results of physical and mechanical properties characterisation revealed that an increase in the amount of SiC particulates incorporated leads to an increase in macrohardness and elastic modulus, which does not affect the 0.2% yield strength and reduces the ultimate tensile strength, ductility, and co...

In the present study, an aluminium–silicon carbide based functionally gradient material was successfully synthesised using a new technique termed here as gradient slurry disintegration and deposition process. The gradient of SiC was successfully established using this technique for 21 wt-%SiC. The results were confirmed using microstructural characterisation techniques, microhardness measurements, and wear rate determination. The results further revealed that an increase in the weight percentage of silicon carbide particulates along the deposition direction lead to a concurrent increase in porosity, degree of clustering, and microhardness while the nature of silicon carbide/aluminium interfacial integrity remained the same. The results of wear rate determination indicated that a difference of ∼9.53 vol.-%SiC on the opposite faces of the functionally gradient material led to the wear resistance increasing to ∼31.5× that of the high aluminium end. An attempt is made to interrelate the processing met...