Optimum Combination Of Properties Research Articles

Processing-microstructure-property correlation in thermo-mechanically processed Ti-6Al-4V alloys: A comparative study between conventional and novel approaches

Ti-6Al-4V alloy offers an optimum combination of properties like strength, ductility, toughness, corrosion and fatigue resistance. Interestingly, thermomechanical processing (TMP) appears as an important technique to tailor the microstructure and therefore modifying the properties further. In the present study, two different TMP routes having minor differences in the processing conditions are used. While one of the routes is a conventional one to generate bimodal microstructure, the other one employs a novel approach with nominal variation in the parameters for the initial steps of TMP. Consequently, the as-received lamellar structure transformed into an equiaxed one, instead of a bimodal. To gain a deeper insight, the dominant mechanisms for microstructural evolution following each TMP steps are critically analyzed. Particular focus was to identify the variation in micromechanism with the alteration in the processing parameters, employed in the new approach. The corresponding effects in modifying the localized and globalized mechanical properties of the as-received and processed alloys are investigated extensively and the microstructure-property correlations are established. While the alloy in as-received condition revealed the least hardness, the equiaxed one obtained with the novel TMP approach showed the highest value, even improved from the bimodal microstructure. The role of individual constituents in affecting the hardness of the alloys are further evaluated. The research also emphasizes that the studied Ti-6Al-4V alloy in the form of different microstructures (lamellar, bimodal, equiaxed) do show indentation size effect leading to increased hardness with reduced load. The equiaxed structure is however least prone to the size effect, thereby revealing lesser variation in properties for small-scale applications. Furthermore, the equiaxed microstructure also exhibited a combination of higher global strength and ductility, as realized from tensile tests. The study is the first of its kind to highlight the scope for generating the equiaxed microstructure in Ti-6Al-4V alloy, through a novel processing route, leading to the best possible combination of mechanical properties.

Coconut Shell Particle Reinforced Al-Cu-Mg Nanocomposites for Cavity Die Mould Parts Applications

This study explored coconut shells in developing Al-Cu-Mg based nanocomposites for fabricating mould parts. The aim is to engineer alternate way through which income can be generated from agricultural wastes and recycling of industrial waste like aluminium cans. Al-Cu-Mg based nanocomposites were produced and characterised. Effects of carbonised and uncarbonised coconut shell nanoparticle (UCSNP) additions on properties of Al-Cu-Mg nanocomposites were compared. Maximum tensile strength was obtained at 10%vol uncarbonised coconut shell nanoparticle additions to Al-Cu-Mg. Increase in tensile strength and elastic modulus were noted with carbonised coconut shell reinforced Al-Cu-Mg nanocomposites against the decrease in the elastic (Young’s) modulus of the UCSNP/Al-Cu-Mg nanocomposites. Despite highest tensile strength of 10%volUCSNP/Al-Cu-Mg, 10%volCCSNP/Al-Cu-Mg nanocomposite is ranked as the best material in this study due to its optimum combination of properties including tensile strength, elastic modulus, tensile strain, impact energy and hardness values. Hence, it has been selected for fabricating open die mould parts to be used in compression sheet forming process for fabricating polymeric standard samples for tensile flexural analyses. Keywords: Al-Cu-Mg, Coconut, Shell, Nanoparticles, Mould fabrication

Abradable coatings: Design through microstructure based models

Improvised sealing methods are required between rotating and stationary parts in aircraft engines to improve the engine performance significantly by improving thermal efficiencies. To achieve this, use of abradable coatings/seals are proposed. With an abradable seal, blade tip incurs into the shroud, thereby reducing the gap between rotor and the shroud to a minimum. Abradable coatings are generally multiphase materials applied using thermal spray techniques. The most common three phases are metal matrix, oxide particles, and porosity. Effectiveness of seal is determined by optimum combination of properties like erosion resistance and hardness; and this is achieved by maintaining proper combination of the ingredients while manufacturing. The present study intends to develop theoretical/modeling approach to study these materials and develop design and property prediction capability in order to come up with best abradable materials. This modeling approach seems to provide consistent results and these results can be used as a reliable starting point in further coatings design.

Изучение влияния различных растворителей на свойства гидрофобных кремнеземных ксерогелей

Silica aerogels are low-density inorganic aerogels with a three-dimensional nanoporous structure. Due to the inherent properties of nanoporous materials, the possibility of using silica airgel is of great interest in various fields. To simplify the process and reduce costs, the use of atmospheric pressure drying (APD) is promising, the resulting materials are called xerogels. Silica xerogels based on methyltrimethoxysilane were synthesized using various alcohol solvents. The optimal combination of properties is possessed by a sample obtained using methanol as a solvent. The wetting angle of all xerogels was 158°, which characterizes the resulting material as superhydrophobic.

Effects of Zr on microstructural evolution and mechanical property of Cu-15Ni-8Sn alloy

The Cu-15Ni-8Sn-XZr (wt.%, X=0–0.7) alloys were prepared by vacuum melting, and their microstructural evolutions during the solidification and heat-treatment processes were systematically investigated as well as the corresponding mechanical properties. Zr addition could offer a significant effect on the dendritic morphology by controlling the constitutional supercooling in solidification front, and it also made the γ-phase more likely to form in the needlelike-shape rather than the lamellar-like shape in subsequent cooling process. After solution treatment, the Zr atoms with a low content of 0.1 wt% were completely solidly dissolved in the α-matrix. With its content increasing to 0.3 and 0.5 wt%, the existence form was changed into the nano-scale precipitation phase (Ni5Zr) and then to micron-scale segregation phase (Ni4SnZr). The presence of Zr could significantly extend the aging window of alloy and improve its mechanical properties by inhibiting the nucleation and growth of discontinuous precipitation (DP), and there was few DP even after 16 h aging. The optimal combination of properties was obtained for Cu-15Ni-8Sn-0.5Zr alloy aged at 673 K for 4–16 h, including a hardness of 330HB, ultimate tensile strength (UTS) of 980 MPa and electrical conductivity of 9%IACS.

In state of art: Mechanical behavior of natural fiber‐based hybrid polymeric composites for application of automobile components

AbstractEnvironmental and sustainability issues coupled with increased awareness have urged researchers to focus on natural sources that can substitute several forbidden materials. Fiber‐reinforced hybrid polymeric composites have succeeded in attracting global attention toward its suitability to replace conventional materials. Hybrid fibers have recently become immensely popular with polymer composite reinforcements for various automotive parts. Hybrid composites are developed by blending natural, synthetic, or a combination of natural or synthetic fibers in a single matrix. Hybridization allows enhancements in physical, mechanical, and thermal properties of the composites. Hybrid composites assist in achieving an optimum combination of properties than individual fiber composites. In this paper, a comprehensive review of the properties of composite reinforcement natural fibers for the application of automobile components is presented. Recent articles on emerging fiber types are reviewed and fabrication techniques required for hybrid polymer composites are discussed. A prospective study is also presented and discussed of future trends in natural fiber applications as well as needed innovations for extending their applications.

An investigation of mechanical properties of aluminium based silicon carbide (AlSiC) metal matrix composite by different manufacturing methods

Abstract The effect of reinforcement material and manufacturing process on the mechanical properties of non-asbestos material has been studied. Metal matrix composites (MMCs) shows good properties from the combination of a soft material like aluminium or magnesium with hard reinforcement material such as silicon carbide (SiC) or graphite. Such composites are formed by regulating the constituent surface morphology to obtain the optimum combination of properties. The properties of the composites depend on the characteristics of the components, their relative quantity, and the structure of the dispersion process consisting of the size, shape, and orientation of the particle in the matrix. Mechanical properties and microstructural analysis of Al-SiC Composites produced under different process conditions were investigated in this work to understand their process structure–property relationships through the optimization method. The addition of silicon carbide particles to base material aluminium has shown improved mechanical properties.

Effect of thermomechanical cyclic quenching and tempering treatments on microstructure, mechanical and electrochemical properties of AISI 1345 steel

Thermomechanical cyclic quenching and tempering (TMCT) can strengthen steels through a grain size reduction mechanism. The effect of TMCT on microstructure, mechanical, and electrochemical properties of AISI 1345 steel was investigated. Steel samples heated to 1050°C, rolled, quenched to room temperature, and subjected to various cyclic quenching and tempering heat treatments were named TMCT-1, TMCT-2, and TMCT-3 samples, respectively. Microstructure analysis revealed that microstructures of all the treated samples contained packets and blocks of well-refined lath-shaped martensite and retained austenite phases with varying grain sizes (2.8–7.9 µm). Among all the tested samples, TMCT-3 sample offered an optimum combination of properties by showing an improvement of 40% in tensile strength and reduced 34% elongation compared with the non-treated sample. Nanoindentation results were in good agreement with mechanical tests as the TMCT-3 sample exhibited a 51% improvement in indentation hardness with almost identical reduced elastic modulus compared with the non-treated sample. The electrochemical properties were analyzed in 0.1 M NaHCO3 solution by potentiodynamic polarization and electrochemical impedance spectroscopy. As a result of TMCT, the minimum corrosion rate was 0.272 mm/a, which was twenty times less than that of the non-treated sample. The impedance results showed the barrier film mechanism, which was confirmed by the polarization results as the current density decreased.

Effect of cold rolling on aging precipitation behavior and mechanical properties of Cu–15Ni–8Sn alloy

The present study investigated the aging precipitation behavior and mechanical, electrical properties of Cu–15Ni–8Sn alloy affected by cold rolling with different deformations. During cold rolling, the grain is elongated gradually along rolling direction with increasing deformation, simultaneously accompanied by the occurrence of a great deal of dislocations and deformation twins. During aging process, the coherent DO22 and L12 ordered phases precipitate successively from the matrix after 90% rolling deformation and aging treatment at 400 °C for 0.5 h with the orientation relationship of (1¯10)DO22 // (022¯)Cu, [111]DO22 // [211]Cu; (11¯1¯)L12// (11¯1¯)Cu, [211]L12 // [211]Cu. However, discontinuous precipitation (DP) behavior is significantly accelerated by prior cold rolling. On the one hand, by revealing the underlying growth kinetics of DP, it can be found that the nucleation sites of DP transform from grain edges to grain boundaries gradually with increasing rolling deformation. On the other hand, the nucleation sites and nucleation rate of DP can be enhanced greatly with increasing dislocation density. Furthermore, the interlamellar spacing of DP slightly increases and the morphology transforms from lamellar structure to bush-like structure gradually with increasing rolling deformation. In addition, the hardness, tensile strength and electrical conductivity are obviously improved while the peak aging time greatly shortens with increasing rolling deformation. The optimal combination of properties with a hardness of 409 HV, a yield strength of 1256 MPa, and an electrical conductivity of 7.5 %IACS can be obtained in the sample with 90% rolling deformation after aging treatment at 400 °C for 0.5 h. The corresponding strengthening mechanism and conductive mechanism were discussed. It can be discovered that the precipitation strengthening, dislocation strengthening and solid solution strengthening are believed to be the main strengthening mechanisms to enhance the alloy strength.

Effect of post-ECAP aging on the microstructure, hardness and impact behaviour of 6061 Al alloy

The effect of post-ECAP aging on the microstructure, hardness and impact behaviour of peak aged 6061 aluminium alloy after a single pass was studied in this work. SEM observations revealed the presence of the strengthening phase of Mg2Si of varying morphology within the matrix of the as-received, T6 tempered alloy and post-ECAP aged samples. The ECAPed alloy showed a significant increase in hardness with a decline in notch toughness than the as-received alloy. Application of post-ECAP aging on the ECAPed alloy resulted in a further increase in the hardness and notch toughness of the post-ECAP aged alloy when compared with the ECAPed alloy. This can be ascribed to the precipitation of the strengthening phase which predominates the recovery of the matrix during the post-ECAP aging process. Hence, post-ECAP artificial aging resulted in an optimum combination of properties of the investigated 6061 aluminium alloy.

BaCe0.7–xZr0.2Y0.1FexO3–δ derived from proton-conducting electrolytes: A way of designing chemically compatible cathodes for solid oxide fuel cells

The present study describes the rational engineering, preparation and characterisation of new mixed ionic-electronic conductors (MIECs) having great potential for application in solid oxide fuel cells (SOFCs) based on proton-conducting electrolytes. The developed MIECs are derived from promising Ba(Ce,Zr)O 3 -materials doped with iron as a transition element: BaCe 0.7–x Zr 0.2 Y 0.1 Fe x O 3–δ (x = 0–0.7, Δx = 0.1). The comprehensive analysis of the functional properties (crystal structure, densification, microstructure, defect structure, thermal expansion behaviour, electrical conductivity) indicate that a moderate iron content is beneficial in order to achieve a certain compromise. In detail, the gradual Fe-doping results in an enhancement of transport properties (including, ionic-electronic conductivity level) and deterioration of mechanical characteristics (an increase of average thermal expansion coefficient values). The composition with x = 0.6, identified as more optimal, was used as a cathode for an intermediate-temperature SOFC; this cathode displays a satisfactory polarisation resistance level, 0.21 Ω cm 2 at 700 °C, without the use of any additional electroactivation technique. The obtained results indicate that BaCe 0.7–x Zr 0.2 Y 0.1 Fe x O 3–δ MIECs having one of the highest chemical compatibility with state-of-the-art proton-conducting electrolytes can be considered as advanced electrodes for designing new solid oxide electrochemical devices with prolonged and stable operation mode. • BaCe 0.7–x Zr 0.2 Y 0.1 Fe x O 3–δ (BCZYFx) materials were prepared for the first time. • The BCZYFx materials are single-phase across the entire x range (0 = x ≤ 0.7). • Fe-doping leads to an increase in both ionic and electronic conductivities (at x ≥ 0.4). • At the same time, TECs values increase and chemical strain becomes more pronounced. • BCZYF0.6 with an optimal combination of properties was utilised as a SOFC cathode.

Evaluation of the suitability of Fe40Co30Ni30 as a precursor for Fe-rich FeCoNi-based high-entropy semi-hard magnets

We evaluated the suitability of Fe40Co30Ni30 as a precursor for Fe-rich FeCoNi-based high-entropy semi-hard magnets. Mechanically alloying the metal powders 40 at.% Fe, 30 at.% Co, and 30 at.% Ni for 12 h effected micron-size Fe40Co30Ni30 powder comprised of nanocrystalline γ phase. Fe40Co30Ni30 evinced semi-hard magnetic properties at room-temperature—saturation magnetization (MS) ~146 Am2/kg and intrinsic coercivity (HCI) ~4.30 kA/m—as well as at below-room-temperatures. The MS at 0 K, μH, and HCI at 0 K were estimated as ~155 Am2/kg, ~1.60 μB, and ~7 kA/m, respectively. Alloy powders after thermal-treatment exhibited tunable semi-hard magnetic behavior at below-room temperatures and room temperature; their magnetic properties were comparable to certain commercial semi-hard magnets. The weighted Euclidean distance-based approach of decision-making proposed the Fe-rich FeCoNi medium-entropy alloy—Fe40Co30Ni30—as a favorable precursor, having an optimal combination of properties, for designing and fabricating novel FeCoNi-based high-entropy semi-hard magnets.

Production, Structurization, and Properties of Wear-Resistant ‘Iron–Carbon Alloy–Granular Hardmetal Reinforcement’ Materials

The production, structurization, and resultant properties of metal matrix ‘iron–carbon alloy–granular hardmetal reinforcement’ materials are studied. The vacuum suction method ensures almost complete filling of interparticle voids with molten metals and results in composites containing hardmetal reinforcement with 0.17–0.7 mm particles. The composites show the microstructure that has no pronounced transition zone at the hardmetal–metal interface and has a ‘granular’ austenitic cast iron matrix and a significant amount of lamellar graphite. The mechanical properties and abrasive impact wear resistance of the white cast iron and carbon steel materials are examined. The optimum combination of properties is exhibited by the composite consisting of steel 45 and 60 vol.% KKhNF15 hardmetal.

Effect of sintering temperature on the densification and optical properties of spark plasma sintered ZnSe ceramics

AbstractIn the present study, ZnSe ceramics were sintered at different temperatures in the range of 900 °C to 1 100 °C by spark plasma sintering. Microstructure, hardness, phase composition, and the optical properties of the ceramics were investigated by scanning electron microscopy, micro-Vickers hardness, X-ray diffraction and Fourier-transform infrared spectroscopy. The results indicated that temperature has a strong effect on grain growth as well as on reducing porosity and improving the properties. The optimal combination of properties (99.5 % density, 165 kg mm−2 hardness and 30 % transmission) was achieved after sintering at 1 100 °C for a holding time of 10 min with an applied pressure of 90 MPa. Furthermore, the grains tended to orient along the spark plasma sintering direction via preferential grain growth that was observed by X-ray diffraction and scanning electron microscopy.

Optimum heat treatment of aluminum alloy used in manufacturing of automotive piston components

ABSTRACTMany automotive components that were earlier made of cast iron are now using aluminum alloys due to their lower weight, better castability, corrosion resistance, and strength at elevated temperatures. Heat treatment is a major processing step in the manufacturing of aluminum-based piston components. The current paper discusses an optimum heat treatment strategy for AC8H aluminum alloy for improved performance. Solutionizing (for homogenization) is followed by aging at different temperatures. Tensile, impact, and hardness tests are performed on untreated and heat treated specimens. Structural analysis (microscopy) is done to understand the changes in mechanical properties. Fractography is also carried out to identify fracture mechanisms under gradual and impact loads. Yield strength, ultimate strength, hardness, and impact toughness show significant increase when aged at 150°C and 175°C (maximum values of 80 MPa, 177 MPa, 28 HRA, and 5.25 J respectively) but decrease at 200°C. SEM micrographs of fracture surfaces show ductile, brittle, and mixed-mode failure patterns for different samples. Observed structural changes are in line with changes in the mechanical properties. It can be concluded that optimum combination of properties is obtained when specimens are aged at 175°C. These findings are of direct utility for academicians, researchers, and practitioners involved in design and manufacture of automobile and other engineering components.

Synthesis of UV-curing waterborne polyurethane-acrylate coating and its photopolymerization kinetics using FT-IR and photo-DSC methods

Environmentally friendly waterborne polyurethane-acrylate (WPUA) oligomers and ultraviolet curing WPUA films (UV-WPUA) were prepared. The thermal stability, solvent-resistance and mechanical properties of the films were investigated. FT-IR and photo-DSC methods were used to investigate the photopolymerization kinetics of the UV-WPUA films. The results showed that UV-curing films offered the optimum combination of properties when the polyether polyol (NJ-330), isophorone diisocyanate (IPDI), hydroxyethyl methyl acrylate (HEMA) and dimethylolbutanoic acid (DMBA) were used as the raw materials and the mass ratio of oligomer: monomer butyl acrylate (BA): photoinitiator was fixed at 66:30:4. Reaction kinetics of different photoinitiators systems were calculated by Kissinger equation and Crane equation, thus providing a theoretical guidance for the optimization of diluent and photoinitiator in UV-curing coating industry.

Multimodal nanoparticle imaging agents: design and applications.

Molecular imaging, where the location of molecules or nanoscale constructs can be tracked in the body to report on disease or biochemical processes, is rapidly expanding to include combined modality or multimodal imaging. No single imaging technique can offer the optimum combination of properties (e.g. resolution, sensitivity, cost, availability). The rapid technological advances in hardware to scan patients, and software to process and fuse images, are pushing the boundaries of novel medical imaging approaches, and hand-in-hand with this is the requirement for advanced and specific multimodal imaging agents. These agents can be detected using a selection from radioisotope, magnetic resonance and optical imaging, among others. Nanoparticles offer great scope in this area as they lend themselves, via facile modification procedures, to act as multifunctional constructs. They have relevance as therapeutics and drug delivery agents that can be tracked by molecular imaging techniques with the particular development of applications in optically guided surgery and as radiosensitizers. There has been a huge amount of research work to produce nanoconstructs for imaging, and the parameters for successful clinical translation and validation of therapeutic applications are now becoming much better understood. It is an exciting time of progress for these agents as their potential is closer to being realized with translation into the clinic. The coming 5-10 years will be critical, as we will see if the predicted improvement in clinical outcomes becomes a reality. Some of the latest advances in combination modality agents are selected and the progression pathway to clinical trials analysed.This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.

Modification of microstructure and mechanical properties of Al–Zn–Mg/3 wt.% Al2O3 composite through semi-solid thermomechanical processing using variable loads

Abstract The microstructure and mechanical properties of Al–Zn–Mg/3 wt.% Al2O3 composite were modified through a thermomechanical processing technique. The powders were cold pressed and solid state sintered for 90 min under argon atmosphere. Thermomechanical processing was then applied to the solid state sintered samples, which consisted of cold pressing followed by partial remelting for 30 min under argon atmosphere. Four different loads in the thermomechanical processing were used to investigate the effects of compressive loads on the microstructures and the mechanical properties. The results revealed modifications in the microstructure of the thermomechanically processed samples with the optimum combination of properties in the sample modified by applying the load of 250 MPa. Increasing the thermomechanical processing load decreased the amounts of porosity by about 7 %, decreased the average grain size to about 4 μm, enhanced the compressive yield strength to about 295 MPa, and increased the microhardness values from 250 HV to 600 HV. In addition, the energy absorption capacity increased by about three times.

Combining the AFLOW GIBBS and elastic libraries to efficiently and robustly screen thermomechanical properties of solids

Thorough characterization of the thermo-mechanical properties of materials requires difficult and time-consuming experiments. This severely limits the availability of data and it is one of the main obstacles for the development of effective accelerated materials design strategies. The rapid screening of new potential systems requires highly integrated, sophisticated and robust computational approaches. We tackled the challenge by surveying more than 3,000 crystalline solids within the AFLOW framework with the newly developed "Automatic Elasticity Library" combined with the previously implemented GIBBS method. The first extracts the mechanical properties from automatic self-consistent stress-strain calculations, while the latter employs those mechanical properties to evaluate the thermodynamics within the Debye model. The new thermo-elastic library is benchmarked against a set of 74 experimentally characterized systems to pinpoint a robust computational methodology for the evaluation of bulk and shear moduli, Poisson ratios, Debye temperatures, Gr\"uneisen parameters, and thermal conductivities of a wide variety of materials. The effect of different choices of equations of state is examined and the optimum combination of properties for the Leibfried-Schl\"omann prediction of thermal conductivity is identified, leading to improved agreement with experimental results than the GIBBS-only approach.

Effect of Heat Treatments on the Mechanical Properties of DIN 50Cr3 Spring Steel

Abstract: This experimental study was conducted to investigate the optimum combination of properties between ductility and toughness from one hand and strength and hardness from the other hand of a commercial grade of light duty spring steel DIN 50Cr3 having a chemical composition of (0.25 % C, 0.8%Cr , 0.79%Mn , 0.2% Si).A heat treatment process by quenching in both oil or water followed by tempering cycles at different temperatures for various tempering times was adopted. The proper austenitization temperature was found to be 870 C. The structure after quenching reveals the formation of martensite with limited amount of retained austenite. Tempering was performed at different temperatures from 250 to 550 C for prolonged times ranging from 1hr up to 3 hr.It was found that oil quenching provides sensibly higher elastic properties than water quenching particularly in the low tempering temperature range. More ever, by increasing the tempering temperature and time ultimate tensile strength, hardness were gradually decreased while ductility remarkably improved. The resultant microstructure after tempering was characterized by a tempered martensitic structure with simple and complex dispersed carbides. Optimum elastic properties were delivered out of this steel after tempering at 450 C for 1hr.