Increase In Lattice Strain Research Articles

Improvement of high temperature oxidation resistance of additively manufactured TiC/Inconel 625 nanocomposites by laser shock peening treatment

Additive manufacturing has seen large growth due to its numerous process advantages, yet some undesirable defects in additive manufactured (AM) products include pores and micro-cracks. These defects weaken the high temperature oxidation resistance of the final parts. In this work, laser shock peening (LSP) is used as a post-treatment method to change the surface characteristics of selective laser melted (SLM) nano-TiC particle-reinforced Inconel 625 nanocomposites (TiC/IN625). The effects of LSP on surface morphology, residual stress, microhardness, microstructure, and high temperature oxidation behavior of fabricated parts are studied. The results indicate pores in the as-built sample can be closed by the severe plastic deformation, which is induced by LSP. The maximum hardness is found to reach 462 ± 7 HV with a ∼ 460 μm hardened layer, and the surface stress state transforms from tensile to compressive after LSP. The full width at half maximum (FWHM) values of the (111) and (200) diffraction broaden, which can be attributed to grain refinement and an increase in lattice strain in the LSP samples. It is found that LSP causes a large number of columnar dendritic structures in the as-built sample to transform into cellular dendritic structures. Dislocation walls and dislocation tangles with high dislocation density form in the LSP sample. Compared with as-built sample, the LSP samples exhibit lower mass gain after oxidation at 900 °C for 100 h, indicating that LSP samples have greater oxidation resistance at high temperature. The underlying mechanism governing the high temperature oxidation resistance is proposed based on the experimental results. This study shows that LSP can be used as an effective method to modify the surface characteristics of SLM TiC/IN625.

Characterization and thermodynamic study of nanostructured Cu‐26Zn‐4Al (wt.%) shape memory alloy through mechanical alloying

AbstractIn the current study, nanostructured Cu−Zn−Al ternary alloy was synthesized via mechanical alloying. The structural evolutions were also measured using x‐ray diffraction and scanning electron microscope. The results showed an increase in lattice strain while the crystallite size decreased. Afterwards, thermodynamic analysis was carried out on Cu−Zn, Cu−Al and Zn−Al binary systems through Miedema's semi‐empirical model. It was found that in all binary systems, there is a driving force for solid solution formation over all compositions due to its negative Gibbs free energy changes in those compositions, whilst, this value is positive for the formation of amorphous phase over some compositions which can be attributed to the absence of driving force. Finally, the extended version of Miedema's semi‐empirical model was used and discussed in detail to determine the thermodynamic desirability of solid solution and amorphous phase formation for Cu−Zn−Al ternary system. It was concluded that in this ternary system, the minimum thermodynamic driving force for solid solution formation occurred for those compositions which were located in the corners of ternary diagram.

Structural, opto-electronic and photoelectrochemical properties of tin doped hematite nanoparticles for water splitting

For application in photoelectrochemical water splitting, pristine and Sn doped (1%, 3% and 5%) hematite nanoparticles were prepared hydrothermally via a two step heating process. XRD results showed that the products match the rhombohedral crystal system. The peak broadening of hematite nanoparticles due to small crystallite size and strain were analyzed by Scherrer's equation and Williamson Hall plot method respectively. A decrease in crystallite size and an increase in lattice strain is observed with dopant addition. Structural change from nanorods to nanocorals is seen for the Sn doped hematite products. Selected Area Diffraction patterns reveal crystallinity of both the doped and undoped powders. Sn 3d XPS peak analysis reveals that Sn has been doped into the hematite lattice. Linear Sweep Voltammetry and Electrochemical Impedance Spectroscopy analysis confirm that 1% Sn doped hematite has the highest photocurrent density (3 mA/cm2 at 1 V vs. Ag/AgCl) and least charge transfer resistance among the doped products. UV-VIS, Photoluminescence and Mott-Schottky analysis further show that optimum optical and electrical properties are observed for hematite doped with 1% Sn.

Effect of Milling Time on Consolidation of Al5083 Nanocomposite by Equal Channel Angular Pressing

The effect of milling time on consolidation of Al5083-5wt. % nanoyttrium oxide powders which are milled from 0-35 hours using planetary ball mill. nanocrystalline structure was observed after 10hours of milling. X-ray diffraction results reveals the formation of 57nm and 31nm for 20hr and 35hr of milling with increase in lattice strain. Circular and Elliptical morphology of milled powders were confirmed through SEM with decrease in particle size. The 90o die channel angle ECAP die was used to consolidate 20hr and 35hr milled powder aided with and without back pressure. The optical micrographs reveal the formation of fine grains. The35hr milled powder shows the maximum densification of 96% and 20hr milled powder shows maximum hardness of 82HRB was observed in 20hr milled powder. Both are consolidated for two passes in route-A and sintered at 430°C for one hour.

Synthesis and characterization of MnxMg1-xFe2O4 based on natural iron sand prepared by Co-precipitation method

Magnetic nano particles, MnxMg1-xFe2O4 (x = 0.25, 0.5 and 0.75) with natural iron sand as raw material were successfully synthesized by co-precipitation method. The obtained samples were characterized by the x-ray diffractometer (XRD) and the vibrating sample magnetometer (VSM). The XRD result showed that the magnetic nano particles have a single phase of inverse-spinel face cubic center (fcc) structure. Furthermore, the lattice parameter constant, crystallite sizes and unit cell volume decrease with the increase of the x content. Contrary the dislocation density and lattice strain increase with increasing the x content. The VSM result showed that the saturated magnetization magnitude were getting high and the coercive field became low when the x were increased.

Microstructure and thermodynamic analysis of nanostructured Cu-13.2%Al-4%Ni ternary system synthesized by mechanical alloying

Thermodynamic analysis of nanostructured Cu-13.2%Al-4%Ni synthesized by mechanical alloying was studied through Miedema’s semi-empirical model. The variations of lattice strain, crystallite size and microstructural evolution at various milling times were also measured using X-ray diffraction and scanning electron microscope. The results showed an increase in lattice strain and reduction in crystallite size due to an increase in density of structural defects as a result of high-energy collisions during mechanical alloying. The calculated thermodynamic data suggested that in all binary Cu-Al, Al-Ni and Ni-Cu systems, there is a driving force for solid solution formation over all compositions due to negative Gibbs free energy changes in those compositions, while this value is positive for the formation of amorphous phase over some compositions which can be attributed to the absence of driving force. Additionally, thermodynamic data were in agreement with XRD results which showed solid solution was formed at middle stages of mechanical alloying. Moreover, it is concluded that the formation of solid solution is easier at three corners of ternary diagram, where the concentration of one element is major, whilst amorphous phase formation is more desirable in other compositions.

The Electrolytic Ionic Strength Effect on Corrosion Resistance and Crystallinity of Plasma Electrolytic Oxidation (PEO) Coating Developed on Ti6Al4V

The aim of this paper was to investigate the formation of an amorphous phase in the coating structure due to reduction in porosity and improvement in corrosion resistance of Ti6Al4V alloy during PEO process. The effect of crystallization on the electrochemical corrosion behavior and surface property of Ti6Al4V coating fabricated by plasma electrolytic oxidation (PEO) technique, was investigated in 5 wt %HCl solution. The coating compositions and electrochemical behaviors were examined by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) and polarization tests. The results showed that an increase in the ionic strength of electrolyte had a direct effect on the crystal size, the lattice strain and corrosion resistance. An increase in lattice strain due to Ti–O–Si led to a reduction in coating adhesion and corrosion resistance. A significant effect in phase transformation for Titania in the PEO process was not only led to an increase in polarization resistance but also reduced the number and size of porosity.

Investigation on ECAPed structural steel IS2062 and evaluation of strengthening mechanisms

The structural steel IS2062 was processed by equal channel angular pressing (ECAP) at room temperature with 120° channel angle die. The microstructural properties are evaluated and correlated with the mechanical properties of the ECAP processed material. Every subsequent ECAP passes the strength of the sample was improved and the results are attributed by the SPD process which generated higher dislocation density with refined grains. X-ray diffraction line profile analysis was used to determine the crystallite size, lattice strain and dislocation density. TEM analysis confirmed the dislocation structure in deformed samples. The ECAP processed sample exposed an increase in lattice strain and dislocation density with the number of passes and with a reduced crystallite size. Quantitative contributions of individual strengthening mechanisms for the overall yield strength of ECAP sample was analytically calculated. The results illustrate that the significant contribution comes from dislocation density followed by grain boundary strengthening.

Structural, optical and mechanical properties of sol-gel synthesized Mn-doped CeO2

CeO2 has a robust cubic fluorite face centered cubic (f.c.c.) structure. However, substitution in CeO2 can introduce lattice defects, tune optical properties and generate different functionalities. The oxidation state of a substituent triggers a Ce4+→Ce3+ transformation without destroying the structure but modifies the structure by generating defects. These structural changes should affect physical properties such as mechanical hardness along with electrical, optical and other properties. Mn substitution results in considerable changes in lattice parameters. Optical properties are affected. It is the valence state and ionic radius of the substituent which dominate the structural, vibrational and optoelectronic properties. Analysis reveals contraction of unit cell and increase in lattice strain affecting the hardness of the material. Microhardness studies show Indentation Size Effect with dominant plastic deformation.

The Effect of Grinding on Tremolite Asbestos and Anthophyllite Asbestos

The six commercial asbestos minerals (chrysotile, fibrous actinolite, crocidolite, amosite, fibrous tremolite, and fibrous anthophyllite) are classified by the IARC as carcinogenic to humans. There are currently several lines of research dealing with the inertisation of asbestos minerals among which the dry grinding process has received considerable interest. The effects of dry grinding on tremolite asbestos and anthophyllite asbestos in eccentric vibration mills have not yet been investigated. Along the research line of the mechanical treatment of asbestos, the aim of this study was to evaluate the effects of dry grinding in eccentric vibration mills on the structure, temperature stability, and fibre dimensions of tremolite asbestos from Val d’Ala, (Italy) and UICC standard anthophyllite asbestos from Paakkila mine (Finland) by varying the grinding time (30 s, 5 min, and 10 min). After grinding for 30 s to 10 min, tremolite asbestos and anthophyllite asbestos showed a decrease in dehydroxylation and breakdown temperatures due to the increase in lattice strain and the decrease in crystallinity. Moreover, after grinding up to 10 min, tremolite and anthophyllite fibres were all below the limits defining a countable fibre according to WHO.

In situ neutron diffraction in quantifying deformation behaviors of nano-sized carbide strengthened UFG ferritic steel

The microstructures and mechanical properties of a low-alloy medium-carbon steel with a duplex microstructure composed of nanoscale spheroidized carbides in ultrafine-grained (UFG) ferritic steel are examined. The average grain size of the studied steel is ~ 430 nm, and these grains coexist with numerous carbides. Neutron diffraction reveals that the intensity of (011) and (022) peaks for the UFG sample is significantly enhanced, suggesting that the (011)//RD texture is a result of the warm rolling process. The lattice parameter of UFG steel is smaller than that of a martensitic steel (M steel) counterpart, indicating a lower carbon concentration in the lattice. The estimated dislocation densities for M steel and UFG steel are 2.59 × 1014 cm−2 and 1.76 × 1012 cm−2, respectively. The UFG steel reveals a nearly isotropic lattice strain response under initial tension from 0 to 450 MPa, where the lattice strains of the (110), (002), and (112) planes are identical. The increase of lattice strain of the (110) plane becomes smaller than that of the (002) and (112) planes as the stress exceeds 450 MPa, suggesting that the nanosized carbides contribute to the hardening ability by promoting the accumulation of geometrically necessary dislocations around the particles, and the (110) lattice becomes harder compared to the other two planes.

Influence on the structural and magnetic properties of pre-alloyed gas-atomized Fe49Co49V2 powders during mechanical milling

The influence on the structural and magnetic properties of pre-alloyed gas-atomized Fe49Co49V2 powders during mechanical milling was investigated. The powders were mechanically milled for up to 45 h. The powders, before milling, were principally comprised of α-phase. No noticeable phase transformation was observed during mechanical milling of the pre-alloyed powders. Mechanical milling resulted in a gradual decrease in crystallite size to as low as ~10 nm, accompanied by an increase in lattice strain to ~1.2–1.5%. Mechanical milling led to an appreciable reduction in the particle size while the morphology of the milled powders appeared similar once the steady-state was attained. The lattice parameter of the nanostructured powders at steady-state was estimated as 0.2857 ± 0.0004 nm. The saturation magnetization (MS) of the nanostructured powders milled for ~45 h was ~211 ± 1 Am2/kg, and it decreased only by ~6% compared to that of the pre-alloyed gas-atomized powders before mechanical milling. The intrinsic coercivity (HCI) of the pre-alloyed powders was estimated as ~1.4 ± 1% kA/m. The HCI peaked to ~8.4 kA/m during the initial stages of milling and subsequently remained between ~6.5 kA/m to ~6 kA/m, during the later stages of milling. As would be expected, the HCI was strongly dependent on the crystallite size. The ferromagnetic exchange length of the nanostructured powders was estimated to be ~27 nm. The magnetic properties of nanostructured Fe49Co49V2 powders obtained by mechanical milling of pre-alloyed powders had relatively superior magnetic properties compared to the nanostructured powder obtained by mechanical alloying of the constituent elemental powders.

Effect of Sr doping on electrical properties of lead zirconate titanate nanoceramics

ABSTRACTPb1-xSrxZr0.52Ti0.48O3 (PSZT) with x = 0–10 mole % were prepared by sol-gel process. X-ray diffraction (XRD) patterns show both rhombohedral and tetragonal crystal symmetries. Increase in lattice strain due to Sr incorporation results in enhanced dielectric constant and piezoelectric co-efficient (d33).With the increase in temperature relaxation time increases from 10−6 sec to 10−7 sec and spreading factor increases from 0.21 (±0.05) to 0.26 (±0.05) for 10 mole % PSZT. Also, the maximum remanent electric polarization and coercive electric field of 13.64 µC/cm2 and 15.97 kV/cm respectively have been observed for 10 mole % samples.

Improvement in levitation force performance of bulk MgB2 superconductors through coronene powder adding

The effect of coronene (C24H12) addition on the levitation force properties of MgB2 superconductor has been investigated for the first time in this study. The polycrystalline disk-shaped MgB2 + y wt % C24H12 samples (y = 0, 2, 4, 6, 8, 10), were synthesized by a pellet/closed tube method at 850 °C under Ar atmosphere, after hot pressing at 200 °C. XRD analysis indicates a decrease in lattice parameters of coronene added samples and confirms substitution of carbon in boron sites. An increase in lattice strain and a decrease in grain size are observed due to the carbon substitution effect. Vertical and lateral levitation force measurements under zero-field-cooled and field-cooled regimes were carried out at different temperatures of 20, 25 and 30 K. It was found that the coronene addition significantly increases the high-field critical current density of MgB2. The Jc values were obtained as 4.6 × 103 Acm−2 and 1.3 × 104 Acm−2 for pure and 4 wt % coronene added samples at 20 K and 4 T. In addition, the levitation force measurements show that 4 wt % coronene adding is very effective in increasing both the vertical and lateral levitation force performances at 20 K. The maximum levitation force for 4 wt % coronene added sample corresponds to 7.58 N/g whereas the reference sample shows 6.73 N/g at 20 K in ZFC regime. The results point out that the hydrocarbon of C24H12 is an effective carbon-containing additive for MgB2 and can be useful for optimizing the levitation performance of MgB2 superconductors for potential applications.

Surfactant-assisted production of TbCu2 nanoparticles

The production of surfactant-assisted metallic nanoparticles of TbCu2 has been achieved by the combination of high-energy ball milling in tungsten carbide containers and the use of oleic acid (C18H34O2) and heptane (C7H16). The alloys were first produced in bulk pellets by arc melting and subsequently milled for only 2 and 5 h in oleic acid (15 and 30% mass weight). The powders consist of an ensemble of nanoparticles with a TbCu2 lattice cell volume of ≈215 Å3, an average particle diameter between 9 and 12 nm and inhomogeneous lattice strain of 0.2–0.4%, as deduced from X-ray diffraction data. The nanometric sizes of the crystals with defined lattice planes are close to those obtained by transmission electron microscopy. Raman spectroscopy shows the existence of inelastic peaks between 1000 and 1650 cm−1, a characteristic of C18H34O2. The magnetisation shows a peak at the antiferromagnetic-paramagnetic transition with Néel temperatures around 48 K (below that of bulk alloy) and a distinctive metamagnetic transition at 5 K up to 40 K. The Curie-Weiss behaviour above the transition reveals effective Bohr magneton numbers (≈9.1–9.9 μB) which are close to what is expected for the free Tb3+ ion using Hund’s rules. The metamagnetic transition is slightly augmented with respect to the bulk value, reaching H = 24.5 kOe by the combined effect of the size reduction and the lattice strain increase and the increase of magnetic disorder. At low temperatures, there is irreversibility as a result of the existing magnetic disorder. The moment relaxation follows an Arrhenius model with uncompensated Tb moments, with activation energies between 295 and 326 K and pre-exponential factors between 10−11 and 10−13 s. The results are interpreted as a consequence of the existence of a diamagnetic surfactant which drastically decreases the magnetic coupling between interparticle moments.

Synthesis mechanism of sono-chemically prepared mesoporous ZnS nanoparticles

The mechanism of sono-chemically synthesized mesoporous ZnS nanoparticles has been investigated. ZnS nanoparticles were synthesized with a facile and quick method. The sonication process was carried out for several times up to 60 min. The synthesized particles have been characterized with scanning electron microscopy, transmission electron microscopy, high resolution x-ray diffraction, UV–visible technique, diffuse reflectance spectroscopy, Brunauer–Emmett–Teller and Fourier transformation infrared spectroscopy. Based on x-ray diffraction patterns, crystallite size and lattice strain increase with sonication time. Adsorption–desorption results showed that applying the sono-chemistry synthesizing method in the aqueous atmosphere will cause a mesoporous structure. The obtained specific surface area of the synthesized mesoporous ZnS nanoparticles varied from 53 to 58 m2 · g−1. Also the surface areas created from the porosity of the particles varied from 27 to 29 m2 · g−1. Regarding these results, the mechanism of porosity formation during synthesis of nanoparticles has been explained. Photocatalytic behavior of the synthesized particles has been investigated for degradation of methylene blue from aqueous solution. Factors affecting this behavior have been discussed and it was found that interaction between opposing factors caused the specimen synthesized with 40 min sonication time has the best methylene blue degradation efficiency.

Mechanical alloying behavior of Nb–Ti–Si-based alloy made from elemental powders by ball milling process

Nb–Ti–Si-based alloy powders were prepared by mechanical alloying (MA) of elemental particles. The evolutions of morphology, size, phase constituents, crystallite size, lattice strain, composition and internal microstructure, etc., of the alloy powders were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), laser particle size analyzer and transmission electron microscope (TEM) analyses. The alloy particles are gradually refined and their shapes become globular with the increase in milling time. The diffraction peaks of Nb solid solution (Nbss) phase shift toward lower 2θ angles during ball milling from 2 to 5 h, and after that Nbss diffraction peaks shift toward higher 2θ angles with the increase in milling time from 5 to 70 h, which is mainly attributed to the alteration of the lattice parameter of Nbss powders due to the solution of the alloying element atoms into Nb lattice to form Nbss. During ball milling process, the decrease in crystallite size and increase in lattice strain of Nbss powders lead to continuous broadening of their diffraction peaks. A typical lamellar microstructure is formed inside the powder particles after ball milling for 5 h and becomes more refined and homogenized with the increase in milling time. After 40-h-ball milling, the typical lamellar microstructure disappears and a very homogeneous microstructure is formed instead. This homogeneous microstructure is proved to be composed of only supersaturated Nbss phase.

The effect of milling duration on silicon dioxide characterization

This paper reports the study of milling duration on silicon dioxide characterization. The silicon dioxide has undergone mechanical milling treatment from 0 to 100 hours. The product after milling process was characterized by using scanning electron microscopy and X-ray diffraction. Williamson-Hall plot technique was used in this study to analyse the silicon dioxide crystallite size and lattice strain. The longer milling duration resulted in the reduction of crystallite size and increase in lattice strain.

Fabrication and characterization of nano-Y 2 O 3 dispersed W-Ni-Mo and W-Ni-Ti-Nb alloys by mechanical alloying and spark plasma sintering

Abstract In the present investigation, nano-Y 2 O 3 dispersed W-Ni-Mo and W-Ni-Ti-Nb alloys with nominal composition of W 79 Ni 10 Mo 10 (Y 2 O 3 ) 1 (alloy A) and W 74 Ni 10 Ti 5 Nb 10 (Y 2 O 3 ) 1 (alloy B) (all in wt.%) were synthesized by mechanical alloying (MA) for 20 h followed by spark plasma sintering (SPS) at 1000 °C, 1200 °C and 1400 °C for alloy A and at 1400 °C for alloy B, respectively for 5 min at 75 MPa pressure. Higher reduction of crystallite size and increase in lattice strain in alloy B is attributed to increased brittleness caused by Ti addition. Texture intensity and residual stress increases and decreases respectively with increase in SPS temperature. However, alloy B had a higher residual stress compared to alloy A, both sintered at 1400 °C. The sinterability, hardness, compressive strength and wear resistance increased with increase in SPS temperature for alloy A. Alloy B sintered at 1400 °C achieved maximum hardness (11.89 GPa), compressive strength (2.26 GPa) and wear resistance (wear rate: 1.14 × 10 −6 mm 3 /N m). Reduction in grain growth by rapid spark plasma sintering cycle results in substantial improvement in strength, hardness with appreciable ductility as compared to conventionally sintered W-Y 2 O 3 alloys.

Effect of Mg addition on mechanical and thermoelectrical properties of Al–Al2O3 nanocomposite

The effects of Mg addition on mechanical thermo-electrical properties of Al–Mg/5%Al2O3 nanocomposite with different Mg contents (0, 5%, 10% and 20%) produced by mechanical alloying were studied. Scanning electron microscopy analysis (SEM), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) were used to characterize the produced powder. The results show that addition of Mg forms a predominant phase (Al–Mg solid solution). By increasing the mass fraction of Mg, the crystallite size decreases and the lattice strain increases which results from the atomic penetration of Mg atoms into the substitutional sites of Al lattice. The microhardness of the composite increases with the increase of the Mg content. The thermal and electrical conductivities increase linearly with the temperature increase in the inspected temperature range. Moreover, the thermal conductivity increases with the increase of Mg content.