Formation Of Ordered Phase Research Articles

Effect of Cu Additive on the Microstructure and Magnetic Properties of Fe-6.5wt%Si High Silicon Steel by Induction Melting Method

Fe-6.5wt%Si high silicon steel alloy was prepared using the vacuum induction melting method. Ordered phase formation in Fe-6.5wt%Si alloy was inhibited by adding trace Cu and induction cycle heating purification treatment. The microstructure and magnetic properties of high silicon steel were investigated. The results show that with the increase of Cu content, the alloy microstructure first changed from coarse grain to fine isoaxial crystal, followed by strip dendrite, with ordered cracking. The saturated polarization strength of the alloy decreased from 25.1 emu of the sample without adding Cu and heating once to 21.5 emu for seven cycles, the residual magnetic polarization increased from 0.0255 emu to 0.048 emu, the slope of the magnetization curve slowed down, and the coercive force increased from 2.4 Oe to 4.0 Oe. With the increase of cyclic heating times, the microstructure of the alloy without added Cu refined and transitioned from columnar to equiaxial crystals, from isoaxial dendrite to strip with the addition of 0.03 wt%Cu, and from strip to isoaxial structure with the addition of 0.05 wt%Cu. With the increase of cycle heating times, the saturation magnetization strength of the alloy without Cu and with 0.03 wt%Cu alloy increased, while the recalcitrant force reduced. Conversely, the saturation polarization strength decreased for the alloy with 0.05 wt% Cu, and the coercive force was also reduced.

On the order–disorder transformation within a main hardening precipitate in Al–Mg–Si alloys

ABSTRACT The earliest stages of solid-state precipitation in age hardenable alloys, before the first ordered phase formation, are notoriously elusive, yet often of central importance to material properties quantification. The order–disorder precipitate transformations are currently accepted to proceed by long-range chemical ordering on a substructure extending through the particle, with the Al–Mg–Si alloy Guinier-Preston (GP) zone → β″ transformation representing the most well-documented example. It is shown here that the structurally distinct β″ phase arises directly from solute diffusion-controlled precipitation within a precipitate, providing an alternative pathway for the transformation of one precipitate to a more thermodynamically stable precipitate. The emergence of dispersed β″ nuclei in the otherwise fcc-based particle is revealed by structural and chemical signs of a significant spatial solute variation. Furthermore, upon reduced aging temperature, heavily structurally flawed final particles result from increasingly challenging nucleus coalescence. The highly localised origin of this process suggests that early-stage precipitate transformation mechanisms be revisited for other age hardenable alloys.

Effect of Mo and W underlayers on ordered phase formation in Fe-Au-Pd multilayer thin films at low temperatures

Fe-Pd based thin films with Au intermediate layer fabricated on different substrates (SiO2, SiO2/Mo, SiO2/W) were investigated at annealing temperatures up to 460°C. The samples were deposited by magnetron sputtering and were post-annealed in vacuum. The ongoing processes were investigated by chemical depth profiling and X-ray diffraction. The experimental results showed that the intermediate Au layer always promoted the formation of FePd3 phase which also showed L12 ordered structure except in one case with W underlayer. However, in the samples with Mo buffer but without the Au interlayer the FePd phase formed and L10 ordered phase also appeared for one stacking order. Considering the low diffusivity arising from the annealing temperature the processes were explained by grain boundary diffusion induced reaction layer formation. The formation of the ordered FePd phases was interpreted by the stress accumulation due to the different diffusivity of the components, which relaxes by the shift of the grain boundaries and the transformation of swept over regions. It was concluded, that the effect of the Au interlayer is dominant over the effect of the Mo or W buffer layers.

Size Tuned Synthesis of FeOOH Nanorods toward Self-Assembled Nanoarchitectonics.

Various studies were performed to fabricate self-assembling nanoobjects out of noble metals, but a few efforts were made for engineering iron-based nanorods toward sell-assembling blocks. In this regard β-FeOOH nanorods were fabricated in various sizes to achieve iron-based rod nanoblocks with self-assembling potential. Hydrolysis of ferric ions in various concentrations was successfully developed as a novel approach to control the growth of β-FeOOH crystals and tuning the length of rods in the nano range, below 100 nm. It was found that the concentration of ferric ion has no effect on the widths of nanorods, but the length was affected. By increasing the concentration of ferric ions, an increase in the length of nanorods and an increase of aspect ratio occurred. All sizes of the resulting FeOOH nanorods exhibited mesoporous feature, but interestingly the hysteresis loops were different due to different pore patterns. In fact, pores on the larger particles were more uniform in size and shape. Nanorods of small length did not make suitable interactions toward ordered phase formation, but rods with the mean length of about 90 nm or longer, at a certain concentration, were able to form nematic phases. The large (∼+40 mV) zeta-potential of nanorods prevents formation of dense arrays, and just bundle-like structures were observed. These findings highlight the importance of size, surface charge, and concentration of nanoobjects in the formation of 3D structures. The developed technique in the fabrication of β-FeOOH nanorods provides pure structures that are free from any size-controlling agent. These pure structures are suitable for further functionalization or coating. Self-assembling nanoobjects is a developing field in nanotechnology, and therefore studies can help our understanding over the assembling process.

Formation and Stabilization of 18R Long-Period Stacking Order Phase Through Friction Stir Processing of Mg-Gd-Y-Zn Alloy

The present work deals with the formation and stabilization of the 18R lamellar long-period stacking order phase (LPSO) through friction stir processing of a GWZ magnesium alloy. In this regard, the formation sequence was investigated in detail, where the metastable LPSO structures were formed in the matrix and then transformed into the 18R structure. The involved micro-mechanism is also discussed with emphasis on the formation of a GP-like zone using high-resolution transmission electron microscopy.

Thermodynamic Tuning of Au–Ag–Cu Nanoparticles with Phase Separation and Ordered Phase Formation

Metallic nanoparticles have been widely studied because of their unique and potentially useful optical properties, and are expected to be applied to high-performance photo-catalyst and sensing. Esp...

Ordered phase formation in Sm-Co1−Cu and Er-Co1−Cu alloy films prepared on Cr(100) single-crystal underlayer

Abstract Sm17(Co1−xCux)83 and Er17(Co1−xCux)83 (at. %, x = 0–1) alloy thin films are prepared on Cr(100) single-crystal underlayers at 500 °C by molecular beam epitaxy. The effect of Cu/Co composition on the ordered phase formation is investigated. Sm17(Co1−xCux)83(11 2 ¯ 0) films with hexagonal Sm(Co,Cu)5 (D2d) ordered phase grow epitaxially on the underlayers for all the compositional range of x = 0–1. On the contrary, the structure of Er17(Co1−xCux)83 film varies depending on Cu composition. Amorphous phase is formed in the Er17Co83 (x = 0) film. Er17(Co1−xCux)83(11 2 ¯ 0) epitaxial films with Er(Co,Cu)5 (D2d) ordered phase are obtained for the compositional range of x = 0.25–0.5. With further increasing the x value, the crystallographic phase varies to a phase other than D2d. Partial substitution of the Co sites in ErCo5 structure with Cu atoms and control of the amount of Cu atom are important to stabilize the Er(Co,Cu)5 phase.

Influence of Stress and Strain on <inline-formula> <tex-math notation="LaTeX">$L 1_{0}$ </tex-math> </inline-formula>-Ordered Phase Formation in FePt Thin Film

Effects of stress and strain in FePt thin film on $L 1_{0}$ ordering are investigated by employing single-crystal substrate of which lattice mismatch with FePt crystal is varied in a range from −10.3% to +0.8% for 10 nm thick FePt thin film. Thin films are prepared under different conditions; direct deposition at 600 °C, two-step process consisting of 200 °C deposition followed by 600 °C annealing, and the two-step process with MgO cap layer formed on top of the FePt layer at 200 °C. Formation of $L 1_{0}$ -FePt(001) crystal and $L 1_{0}$ ordering is enhanced on a substrate with larger negative lattice mismatch, though the lattice mismatch with substrate is decreased greatly by introduction of misfit dislocation and by lattice bending in FePt material. The lateral in-plane strain in FePt material associated with several factors: substrate material, film morphology, and cap layer has given a strong influence in $L 1_{0}$ -ordered phase formation in FePt thin film.

L10 ordered phase formation at solid state reactions in Cu/Au and Fe/Pd thin films

To understand the mechanism of mass transfer during solid state reactions and order-disorder transitions the formation processes of CuAuI and L10-FePd ordered structures at solid state reactions in Cu/Au и Fe/Pd bilayer thin films have been carried out using the method of in situ electron diffraction (ED). The value of the long-range order (LRO) parameter has been estimated for the L10 type ordered structures being formed; the order-disorder transition temperatures have been determined. The formation mechanism of the L10 type ordered structures formed at the initial stages of the solid state reaction in the Cu/Au and Fe/Pd thin films has been suggested. In the case of Cu/Au it has been shown that the interdiffusion of copper and gold at the initial stage of the solid state reaction results in the reduced size of the grains of the initial materials, as a result, nanocrystalites of the Cu-Au solid solution are formed, and further, grains of the CuAuI ordered solid solution appear and their growth begins.

Surface Charge Influence on the Phase Separation and Viscosity of Cellulose Nanocrystals.

A series of four cellulose nanocrystal (CNC) suspensions were prepared from bleached softwood kraft pulp using different conditions of sulfuric acid hydrolysis. The CNCs were identical in size (95 nm in length × 5 nm in width) but had different surface charges corresponding to the harshness of the hydrolysis conditions. Consequently, it was possible to isolate the effects of surface charge on the self-assembly and viscosity of the CNC suspensions across surface charges ranging from 0.27%S to 0.89%S. The four suspensions (never-dried, free of added electrolyte) all underwent liquid crystalline phase separation, but the concentration onset for the emergence of the chiral nematic phase shifted to higher values with increasing surface charge. Similarly, suspension viscosity was also influenced by surface charge, with suspensions of lower surface charge CNCs more viscous and tending to gel at lower concentrations. The properties of the suspensions were interpreted in terms of the increase in effective diameter of the nanocrystals due to the surface electrostatic repulsion of the negative sulfate half-esters, as modified by the screening effects of the H+ counterions in the suspensions. The results suggest that there is a threshold surface charge density (∼0.3%S) above which effective volume considerations are dominant across the concentration range relevant to liquid crystalline phase formation. Above this threshold value, phase separation occurs at the same effective volume fraction of CNCs (∼10 vol %), with a corresponding increase in critical concentration due to the decrease in effective diameter that occurs with increasing surface charge. Below or near this threshold value, the formation of end-to-end aggregates may favor gelation and interfere with ordered phase formation.

Self-learning kinetic Monte Carlo simulations of diffusion in ferromagnetic α-Fe–Si alloys

Diffusion of Si atom and vacancy in the A2-phase of α-Fe–Si alloys in the ferromagnetic state, with and without magnetic order and in various temperature ranges, are studied using AKSOME, an on-lattice self-learning KMC code. Diffusion of the Si atom and the vacancy are studied in the dilute limit and up to 12 at.% Si, respectively, in the temperature range 350–700 K. Local Si neighborhood dependent activation energies for vacancy hops were calculated on-the-fly using a broken-bond model based on pairwise interaction. The migration barrier and prefactor for the Si diffusion in the dilute limit were obtained and found to agree with published data within the limits of uncertainty. Simulations results show that the prefactor and the migration barrier for the Si diffusion are approximately an order of magnitude higher, and a tenth of an electron-volt higher, respectively, in the magnetic disordered state than in the fully ordered state. However, the net result is that magnetic disorder does not have a significant effect on Si diffusivity within the range of parameters studied in this work. Nevertheless, with increasing temperature, the magnetic disorder increases and its effect on the Si diffusivity also increases. In the case of vacancy diffusion, with increasing Si concentration, its diffusion prefactor decreases while the migration barrier more or less remained constant and the effect of magnetic disorder increases with Si concentration. Important vacancy-Si/Fe atom exchange processes and their activation barriers were identified, and the effect of energetics on ordered phase formation in Fe–Si alloys are discussed.

Strengthening mechanisms in Fe-Al based ferritic low-density steels

Low-density steels with different aluminium contents have been investigated with an aim to examine the occurrence of different strengthening mechanisms leading to its higher strength. A composition corresponding to 6.8wt% aluminium has been studied to understand the underlying strengthening mechanisms. Different factors contributing to the strengthening mechanisms have been separately analyzed. Microstructural features have been analyzed using Mössbauer spectroscopy, small angle X-ray scattering (SAXS), X-ray line profile analysis and transmission electron microscopy (TEM). The enhanced yield strength of the low-density steel containing 6.8wt% Al was attributed to the strengthening effects arising from the ferrite grain size, dislocations incorporated during processing, ordered phase formation and the presence of Al atoms in the solid solution. Each of these operating mechanisms was modelled by using its constitutive equation for example, grain size strengthening by classical Hall-Petch equation and the strengthening from dislocations by Taylor's equation. In addition, the formation of nano-sized ordered phase was evaluated by TEM, Mössbauer spectroscopy, SAXS and hence order strengthening was modelled by using the size and volume fraction (as determined by TEM and SAXS). Strengthening due to lattice frictional stress required for dislocation motion was also incorporated into the model.

Fe-Ni基ナノ結晶合金におけるL1<sub>0</sub>型規則相の生成

Fe-Ni基ナノ結晶合金におけるL1<sub>0</sub>型規則相の生成

Formation of an ordered phase by ceramides and diacylglycerols in a fluid phosphatidylcholine bilayer — Correlation with structure and hydrogen bonding capacity

Ceramides and diacylglycerols are lipids with a large hydrophobic part (acyl chains and long-chain base) whereas their polar function (hydroxyl group) is small. They need colipids with large head groups to coexist in bilayer membranes. In this study, we have determined how saturated and unsaturated ceramides and acyl-chain matched diacylglycerols form ordered domains in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers as a function of bilayer concentration. The formation of ordered domains was determined from lifetime analysis of trans-parinaric acid. Ceramides formed ordered domains with equal average tPA lifetime at lower bilayer concentration when compared to acyl-chain matched diacylglycerols. This was true for both saturated (16:0) and mono-unsaturated (18:1) species. This finding suggested that hydrogen bonding among ceramides contributed to their more efficient ordered phase formation, since diacylglycerols do not form similar hydrogen bonding networks. The role of hydrogen bonding in ordered domain formation was further verified by using palmitoyl ceramide analogs with 2N and 3OH methylated long-chain bases. These analogs do not form hydrogen bonds from the 2NH or the 3OH, respectively. While methylation of the 3OH did not affect ordered phase formation compared to native palmitoyl ceramide, 2NH methylation markedly attenuated ceramide ordered phase formation. We conclude that in addition to acyl chain length, saturation, molecular order, and lack of large head group, also hydrogen bonding involving the 2NH is crucial for efficient formation of ceramide-rich domains in fluid phosphatidylcholine bilayers.

Influence of Thickness on the Metastable Ordered Phase Formation in CoPt and Co3Pt Alloy Films

Influence of Thickness on the Metastable Ordered Phase Formation in CoPt and Co3Pt Alloy Films

Effect of Composition on the Ordered Phase Formation in Co-Pt Thin Film Deposited on MgO(111) Single-Crystal Substrate

Co x Pt 100-x (at. %) alloy epitaxial films with the close-packed plane parallel to the substrate surface are prepared on MgO(111) substrates heated at 300 °C by varying the Co content of x from 0 to 100. The stacking sequence of close-packed plane (the volume ratios of fcc and hcp crystals, V fcc and V hcp ) and the order degree are quantitatively determined. The films with Pt-rich and nearly equiatomic compositions primarily consist of fcc crystals (V fcc >0.9). With increasing the x value beyond 56, the V hcp value drastically increases. The films with Co-rich compositions consist of mixtures of hcp (V hcp ≈0.8) and fcc (V fcc ≈ 0.2) crystals. The films with 31 ≤x≤ 86 involve metastable ordered phases. The order degree of S L11 ,Bh is kept constant around 0.25 in a compositional range of 31 × 75. From the viewpoints of volume ratios of fcc and hcp crystals and order degree, the crystal structure is determined to vary A1 A1 + SFs (SFs: stacking faults) L1 1 + SFs ⇒L1 1 + Bh (+D0 19 ) ⇒A3 + SFs with increasing the x value. The films including ordered phases show strong perpendicular magnetic anisotropies. It is shown that the uniaxial magnetocrystalline anisotropy energy of Co x Pt 100-x film can be kept >10 7 erg/cm 3 while controlling the saturation magnetization from 600 to 1150 emu/cm 3 .

热处理对挤压变形Mg-7%Zn-0.6%Zr-0.5%Y合金低周疲劳行为的影响 *

对热挤压、时效处理（T5态）及固溶＋时效处理（T6态）Mg-7%Zn-0.6%Zr-0.5%Y合金（质量分数）分别进行了低周疲劳实验,探讨了热处理对合金低周疲劳变形行为的影响.结果表明：时效处理和固溶＋时效处理可提高热挤压Mg-7%Zn-0.6%Zr-0.5%Y合金的循环变形抗力;时效处理降低了合金的疲劳寿命,固溶＋时效处理可以提高合金在较高外加总应变幅下的疲劳寿命,但降低合金在较低外加总应变幅下的低周疲劳寿命;不同状态合金的弹性应变幅和塑性应变幅与载荷反向周次的关系可分别用Basquin和Coffin-Manson公式来描述;时效及固溶＋时效处理过程中形成的长周期堆垛有序结构（LPSO相）是合金的循环变形抗力大幅提高的主要原因,而疲劳变形过程中形成的孪晶可能是时效态合金疲劳寿命降低的原因.

Ordered phase formation in Sm-Ni thin film deposited on Cr(100) single-crystal underlayer

Sm17Ni83 (at. %) alloy thin films are prepared on Cr(100) underlayers hetero-epitaxially grown on MgO(100) single-crystal substrates by employing an ultra-high vacuum molecular beam epitaxy system. The effect of substrate temperature on the ordered phase formation is investigated. The films deposited below 300 °C consist of amorphous phase, whereas formation of SmNi5 ordered phase is recognized for the films deposited above 400 °C. The SmNi5 films with ordered phase consist of two types of (110) variant whose c-axes are lying in the film plane and rotated around the film normal by 90° each other. With increasing the temperature from 400 to 500 °C, the long-range order degree increases from 0.65 to 0.80. The ordered film formed at 500 °C shows an in-plane magnetic anisotropy reflecting the magnetocrystalline anisotropy of SmNi5 crystal.

Effect of Substrate Temperature on the Ordered Phase Formation in Sm–Ni Thin Film Deposited on Cu(111) Underlayer

Sm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sub> Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">83</sub> (at.%) alloy thin films are prepared on Cu underlayers hetero-epitaxially grown on MgO(111) single-crystal substrates by employing an ultra-high vacuum molecular beam epitaxy system. The substrate temperature is varied from 100 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C to 500 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. The film growth behavior and the detailed resulting film structure are respectively investigated by in situ reflection high-energy electron diffraction and by a combination of out-of-plane and in-plane X-ray diffractions. With increasing the temperature up to 300 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, formation of ordered SmNi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> phase is recognized. The films deposited above 400 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C consist of only epitaxial SmNi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> (0001) crystal, whereas the films deposited below the temperature include amorphous phase and/or a hexagonal ordered phase other than SmNi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> . When the temperature is increased from 300 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C to 500 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, the long-range order degree of SmNi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> film increases from 0.60 to 0.97. SmNi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> phase formation is enhanced with increasing the temperature.

FePd, FePt, and CoPt alloy epitaxial thin films with flat surface grown on MgO(111) substrate

FePd, FePt, and CoPt alloy epitaxial films of 40 nm thickness are prepared on MgO(111) singlecrystal substrates by employing two different methods. One is a one-step method consisting of hightemperature deposition at 600 °C and the other is a two-step method consisting of low-temperature deposition at 200 °C followed by annealing at 600 °C. Although the preparation method is different, similar final crystal structures are realized for all the film materials. FePd and FePt alloy films grow on the substrates with six L 10 (111) variants, whose c -axes are about 35° canted from the substrate surface and rotated around the film normal by 60° each other. The order degrees of FePd and FePt films prepared by one- and two-step methods, (S one-step , S two-step ), are estimated to be (0.25, 0.33) and (0.08, 0.15), respectively. On the contrary, L 10 ordered phase formation is not recognized for CoPt alloy films. The films prepared by one-step method have rough surfaces surrounded by side facets, whereas the films prepared by two-step method have very flat surfaces with the arithmetical mean roughness of 0.3 nm. The two-step method is useful for preparation of L 10 ordered films with flat surface.