Increasing Si Content Research Articles

Unraveling the Complex Temperature-Dependent Performance and Degradation of Li-Ion Batteries with Silicon-Graphite Composite Anodes

Competing effects of graphite and Si result in a complex temperature dependent performance and degradation of Li-ion batteries with Si-graphite composite anodes. This study examines the influence of varying the Si content (0 to 20.8 wt%) in Si-graphite composite anodes with consistent areal capacity and N/P ratio in full cells containing NMC622 cathodes. One hundred pilot-scale double-layer pouch cells were built and cycle aged in the temperature range from −10 to 55 °C. Electrochemical characterization demonstrated that increasing Si contents enhance capacity and mitigate internal resistance at low temperatures. On the other hand, high Si contents decrease charge-discharge energy efficiency and cycle life, particularly at elevated temperatures. Post-mortem analysis of aged electrodes, including physico-chemical characterization (scanning electron microscopy, energy-dispersive X-ray analysis, thickness measurements) and cell reconstruction revealed significant solid electrolyte interphase growth and increased loss of active material in anodes with high Si content. The optimum temperature for longest cycle life as derived from Arrhenius plots decreased from 30 °C for graphite anodes to 10 °C for cells with moderate Si content up to 5.8 wt%. These findings allow the design of optimized cells by balancing the Si content versus operating temperature in order to achieve lowest cell aging.

Effect of friction stir processing on grain refinement and superplastic properties of binary Al-8 wt.% Si to Al-30 wt.% Si alloys

ABSTRACT As-cast binary Al–Si alloys containing ∼8, 12, 20, and 30 wt.% Si, representing the hypoeutectic, eutectic (12 wt.% Si), and hypereutectic compositions, were subjected to severe plastic deformation by friction stir processing (FSP) for grain refinement to 2.3–2.7 μm by dynamic recrystallization. Tensile tests conducted by differential strain rate test technique over the strain rates of 10−4 – 10−2 s−1 and test temperatures in the range of ∼840–530 K led to strain rate sensitivity index (m) varying from ∼0.04 to 0.40 depending on temperature, strain rate, and alloy composition. The constant initial strain rate tests conducted at 10−4 s−1 and 840 K exhibited a maximum elongation of 250% in the hypereutectic Al–20Si alloy, but the same increased linearly with m irrespective of alloy composition. Generally, with increasing Si content, the activation energy for deformation increased from 104.7 ± 14.4 kJ/mol for eutectic Al–12Si to 310.4 ± 32.3 kJ/mol for hypereutectic Al–30Si, which increased further to 572 ± 148 kJ/mol over the higher temperature range of 840–800 K. Analysis of observed deformation and microstructure behaviour supports the occurrence of superplasticity, whereby the accommodation of grain boundary sliding by grain boundary migration led to enhanced grain growth or else the local high-stress concentration at the particle-matrix interface led to cavity formation. There was no evidence of dynamic recrystallization during high-temperature tensile deformation but the flow softening observed is ascribed to the occurrence of concurrent cavitation.

Influence of Si Content on the Microstructure, Wear Resistance, and Corrosion Resistance of FeCoNiCrAl0.7Cu0.3Six High Entropy Alloy

This study explores microstructure, wear, and corrosion resistance properties of FeCoNiCrAl0.7Cu0.3Six (x = 0, 0.2, 0.3, 0.5) high-entropy alloys. The FeCoNiCrAl0.7Cu0.3Six alloy contains FCC and BCC structures; as the x increases, the FeCoNiCrAl0.7Cu0.3Si0.2, FeCoNiCrAl0.7Cu0.3Si0.4, and FeCoNiCrAl0.7Cu0.3Si0.5 high-entropy alloys transition to BCC structures. The morphological transition in FeCoNiCrAl0.7Cu0.3Six evolves from bamboo leaf-like intergranular features to a discontinuous intergranular structure as Si content increases. The hardness of these alloys gradually increases with higher Si content. The addition of Si promotes a uniform distribution of Cr within and between grains, reducing the intergranular segregation of Cu. Al and Ni show a consistent pattern of elemental distribution throughout the alloy. Wear measurements of FeCoNiCrAl0.7Cu0.3Six alloys demonstrate that adding Si enhances wear resistance, resulting in smoother wear surfaces with reduced deformation. The wear mechanism for all alloys is primarily abrasive, with no brittle fractures observed. Corrosion resistance is optimized when Si content is 0.2, with pitting corrosion being the primary corrosion form.

Microstructure evolution and degradation process of AlCrTiSiN coatings with different Si contents at high temperatures

The microstructure evolution of AlCrTiN and AlCrTiSiN coatings containing 4, 6.8, and 10.6 at.% Si was studied at temperatures ranging from 800 to 1100 °C. The AlCrTiN coating exhibits a single-phase fcc-(Al,Cr,Ti)N structure, while the AlCrTiSiN coatings transition from a nanocomposite structure, composed of fcc-(Al,Cr,Ti)N and amorphous a-SixNy, to a fully amorphous structure as the Si content increases. The hardness and adhesion strength of coatings initially rise, peaking at 24 GPa and 44 N respectively, due to the formation of the nanocomposite structure. However, these properties decline as the coatings become fully amorphous. At elevated temperatures, severe oxidation leads to the gradual formation of layered oxides. Concurrently, phase transformation, spinodal decomposition, and crystallization occur within the nitride layer. The addition of Si enhances oxidation resistance by promoting the rapid formation of a dense and protective oxide layer, and by reducing nitrogen release and TiO2 formation. However, at 1000 and 1100 °C, the coating with 10 at.% Si exhibits slightly faster oxidation compared to the 6.8 at.% Si coating, as the increased Si content reduces the Al content, limiting the coating's ability to regenerate the protective oxide layer.

Effect of Si additions on the microstructure and properties of Cu-Cr-Mg alloy

Trace Si additions contribute to improve the mechanical properties of Cu-Cr-Mg alloys. The effect of different Si contents (0, 0.06, and 0.16 wt.%) on the microstructure, mechanical, and electrical properties of Cu-0.3Cr-0.2Mg (wt.%) alloys was studied experimentally. It is found that the peak-aged with 0.06 wt.% Si alloy exhibits the highest hardness and strength, mainly due to the moderate refinement of FCC-Cr precipitates by Si addition. However, excessive Si addition (0.16Si) results in the formation of Cr3Si phase, which consumes Cr elements, reducing FCC-Cr precipitation and hence degenerates precipitate strengthening. Results further suggest that the electrical conductivity decreases with increasing Si content due to the increased electron scattering. Thermodynamic calculation reveals that the nucleation driving force of Cr3Si is an order of magnitude smaller than the transformation energy from FCC-Cr to BCC-Cr, suggesting the nucleation of Cr3Si probably precedes the transformation of FCC-Cr to BCC-Cr and thereby facilitates the stabilization of FCC-Cr precipitates. This work provides an insight on understanding microstructural / property evolution of Cu-Cr-Mg-Si alloy and designing high-strength Cu-Cr-Mg alloys through Si addition.

Influence of Si on the Elevated-Temperature Mechanical and Creep Properties of Al–Cu 224 Cast Alloys during Thermal Exposure

The influence of Si content (0.1–0.8 wt.%) on the development of precipitation microstructures and the resultant mechanical and creep properties during thermal exposure, up to 1000 h at 300 °C, in Al–Cu 224 cast alloys, was systematically investigated. The room and elevated temperature yield strength (YS) increased with increasing Si content under the T7 condition, which was attributed to the fact that the Si promoted the precipitation of fine θ′. However, Si increased the coarsening of θ′ during thermal exposure at 300 °C, and the alloys with low Si exhibited a higher YS and creep resistance at elevated temperatures than high Si alloys. The mechanical strength and creep resistance were mainly controlled by the precipitation strengthening of the predominant θ′ phase. Because of the high mechanical strength and creep resistance of the 0.1Si alloy during long-term thermal exposure, the Si level in Al–Cu alloys should be maintained at a low level of 0.1 wt.% for high-temperature applications. The strengthening mechanisms were quantitatively analyzed, based on the characteristics of the precipitate. The predicted YS values under different exposure conditions agreed well with the experimentally measured values.

Extractable soil silicon in relation to sugarcane yield on mineral soil

Florida sugarcane production is mostly on organic soils, but the cultivation area on mineral soils is also expanding. Silicon (Si) is beneficial for sugarcane growth and development on weathered soil. However, the low solubility and availability of soluble Si is an issue in Florida’s mineral soils. This study aimed to assess soil Si extraction methods based on sugarcane yield response to calcium silicate application. It also examined the relationship between sugarcane yield with extracted plant-available soil Si, alongside plant Si concentrations. The experiment followed a randomized complete block design involving 2 fields, with 24 plots each, and 6 replications. Four rates of calcium silicate (0 control, 2.24, 4.48, and 6.67 Mg ha−1) were applied before planting sugarcane. Soil samples were collected prior to planting and after each harvest. Soil Si was extracted using 0.5 M acetic acid, 0.7 N NH4OAc, Mehlich 3, and 0.01 M CaCl2 extractants. Leaf samples were collected over a three-year sugarcane life cycle (from 2019 to 2022) to evaluate the relationship between soil Si and leaf Si concentrations. The relationships between parameters were analyzed using linear and nonlinear regression models. Results indicated that higher Si application rates increased Si concentrations in sugarcane leaves in both fields. However, only one field showed a yield response to Si, likely due to high pre-plant soil Si in the other field. The best extractant should correlate strongly with either yield or leaf Si content, but no single extractant showed a strong correlation with either, making it infeasible to identify the best extractant.

Infrared optical properties of SiGeSn and GeSn layers grown by molecular beam epitaxy

The infrared optical properties of thick GeSn films (>500 nm) having 10% Sn concentration and of SiGeSn layers, utilized for the growth of strain-relieved, direct-gap GeSn films by molecular beam epitaxy, are investigated. Two growth methods are used: a graded-growth structure and a stepped-growth structure that help us to illustrate the properties of the GeSn and SiGeSn layers. Interestingly, there can be strong absorption in SiGeSn films throughout the infrared. We observe an increase in infrared absorption with increasing Sn concentration up to 21% Sn and in films, where the Sn is held constant at 18%, with increasing Si concentration up to 30%. Cavity effects in the infrared transmission measurement of stepped-growth structures are observed and associated with reflections at growth interfaces. Si–Si bond formation is proposed to occur at high Si concentrations in SiGeSn films, and the bandgap in SiGeSn films appears to decrease with increasing Si and Sn concentrations.

Investigation of mechanical properties and high temperature wear resistance of CoFeNi1.5VZr0.4Six high entropy alloys optimized by Si alloying

The current work studies the mechanical properties and high-temperature wear resistance of CoFeNi1.5VZr0.4Six high entropy alloys by Si alloying. The Si alloying transforms Ni7Zr2 into a more wear-resistant silicide phase, and the microstructure changes from lamellar eutectic structure to dendritic structure. The high temperature microhardness, compressive strength and fracture toughness of the HEAs increase first and then decrease with the increasing Si content. The Si alloying in HEAs brings about significant improvements in wear resistance at elevated temperature through the combined effects of phase structure modifications and compositional changes in the tribo-layer. The augmented mechanical properties of the worn subsurface layer contribute to improved wear resistance at elevated temperatures.

Unveiling the precipitation behavior and mechanical properties in G-phase strengthened CrFe2Ni2Ti0.2Six multi-principal element alloys

In order to develop Co-free CrFeNi based multi-principal element alloys (MPEAs) with good synergies between strength and plasticity, the effects of Si content on the microstructures and mechanical properties of CrFe2Ni2Ti0.2Six (x = 0, 0.125, 0.25, 0.375, 0.5 and 0.625) MPEAs are studied in this work. The results show that the addition of Si induces a phase transformation from a single-phase face-centered cubic (FCC) structure to a dual-phase structure, comprising an FCC solid solution phase and G-phase. The outcomes from phase formation theory and phase diagram calculations (CALPHAD) also confirm that CrFe2Ni2Ti0.2Six MPEAs are prone to form dual-phase structures. With increasing Si content, the yield strength and hardness of the alloys increase by 47.2 % and 57.3 %, respectively, while still maintaining a strain of 34.2 %, which is indicative of commendable overall mechanical properties. This is ascribed to the coherence between FCC matrix and G-phase, enabling an enhancement in strength concurrently with the retention of considerable plasticity. Moreover, grain boundary strengthening and precipitation strengthening play a dominant role in the strengthening of CrFe2Ni2Ti0.2Six MPEAs. The present work offers new insights for the further development of high-performance non-metallic MPEAs, so as to achieve a combination of targeted microstructures and excellent properties.

Investigation of the impact of non-magnetic Si element addition and heat treatment on the electromagnetic wave absorption properties of medium entropy FeCoNiSi alloy particles

Based on chemical liquid phase reduction and high temperature annealing, the effects of non-magnetic Si element addition and heat treatment regime on the microstructure, magnetic properties, and electromagnetic wave absorption properties of medium entropy alloy particles FeCoNiSi were studied. The results show that the prepared Fe1Co0.8Ni1Six alloy particles have a spherical structure, and with the increase of Si content, the particle size continuously decreases, with the average particle size decreasing from 150 to 200 nm to 20-50 nm. After high temperature annealing, the alloy particles undergo some agglomeration and growth. The as-prepared Fe1Co0.8Ni1Six alloy particles exhibit an amorphous state, and crystallization occurs during high temperature annealing, but the increase in Si element content has a certain inhibitory effect on the crystallization of the alloy particles. With the increase of Si element content and annealing temperature, the specific saturation magnetization intensity of the material shows a decreasing trend, while the residual magnetism and coercivity show an increasing trend. With the increase of Si element content, the real and imaginary parts of the permeability change alternately in different frequency ranges. The magnetic loss mechanism for the three alloy particles was eddy current loss in the frequency ranges of 10-14GHz and 16.5-18GHz. With the increase of Si element content, the magnetic loss shows an increasing trend, and the impedance matching shows a decreasing trend. The Fe1Co0.8Ni1Si0.5 alloy particle sample has the maximum reflection loss |RLmax| of 28.2 dB at thickness of 2.3 mm, and the Fe1Co0.8Ni1Si0.7 alloy particle sample has an effective absorption bandwidth of 1.7GHz at thickness of 1.9 mm. Eddy current loss was the main magnetic loss mechanism for Fe1Co0.8Ni1Si0.6 alloy particles under 400 °C and 600 °C annealing conditions, and for Fe1Co0.8Ni1Si0.7 alloy particles under 600 °C annealing conditions. With the increase of annealing temperature, the fluctuation of dielectric loss with frequency decreases in the low frequency range, and increases in the high frequency range, while annealing reduces the fluctuation of magnetic loss with frequency. Under 400 °C annealing conditions, the attenuation constant of the three alloy particles was lower than that of the unannealed alloy particles, and under 600 °C annealing conditions, the attenuation constant of Fe1Co0.8Ni1Si0.5 alloy particles in the frequency range of 6-15GHz was higher than that of unannealed and 400 °C annealed alloy particles, and that of Fe1Co0.8Ni1Si0.6 alloy particles in the frequency range of 7-14GHz was higher than that of unannealed and 400 °C annealed alloy particles. High temperature annealing was not able to effectively improve the impedance matching performance of Fe1Co0.8Ni1Six alloy particles. The maximum reflection loss |RLmax| of Fe1Co0.8Ni1Si0.6 alloy particles under 600 °C annealing conditions was 37.8 dB.

Effect of Si content on microstructure and properties of Ti(C, N)-based cermet

The effects of Si additions (0, 0.5 wt%, 1 wt%, 1.5 wt%) on the microstructure, mechanical properties and oxidation resistance of Ti(C, N)-based cermets were investigated. The results showed that Si additions would combine with Mo, which leaded to the formation of MoSi2. Even though the ceramic black core phase was refined, the increase in Si content decreased the wettability between the binder and hard phases. The bending strength of the cermet grew and subsequently declined as the Si content increased, while the hardness did not change much. The most optimized comprehensive properties of the cermets were achieved with Si addition of 1 wt%, The bending strength, hardness and fracture toughness was 2133.7 MPa, 89.6 HRA and 12.21 MPa m1/2 respectively. In another side, cermets with 1 wt% Si addition had lower oxidized weight increase and a thinner oxide film than that without Si. A denser oxidation film composed of SiO2 and NiTiO3 was generated during the oxidation process on the surface of the cermets with Si addition, and this would prevent O elements from diffusion into the cermets, thus the oxidation resistance was enhanced.

Effects of Main Alloying Elements on Interface Reaction between Tool Steel and Molten Aluminum

Effects of Si and Mg as main elements on interface reaction between tool steel and molten Al alloy at 700°C were investigated. Pure aluminum and Al-10mass%Mg alloy showed relatively simple interfacial layers, whereas thicker, multi-layered reaction bonds were found in the diffusion couple of A380 alloy. The diffusion of a large amount of Fe into Al matrix throughout the interfacial layer led to the formation of Al-Fe based intermetallic particles in the Al base metals. The diffusion couple of Al-10mass%Mg alloy showed a similar intermetallic layer as that of pure Al, indicating that 10mass%Mg in the Al melt rarely affected the formation of Al-Fe intermetallic layers. However, A380 alloy showed much expanded soldering area and increased thickness of intermetallic layers. Based on the phase diagram calculated, the solubility of Fe in liquid Al increased significantly with increasing Si content up to apploximately 5mass%, while, in the case of 10mass%Mg addition, the Fe solubility gradually decreased with increasing Mg content. Al-10mass%Mg alloy also showed the same tendency as that of pure Al in the formation and distribution of intermetallic compounds. However, in the Al-12mass%Si alloy, two types of Al-Fe-Si ternary compounds are present on the Al-rich side.

High-temperature hardness and scratch behaviour of differently strengthened iron aluminide laser claddings

Fe3Al-based iron aluminides provide notable high-temperature properties at a comparatively low overall ecological impact. To improve their wear resistance, different strengthening strategies are studied for which Fe3Al-based laser claddings (30 at.% Al) are alloyed either with Si, C, or Ti and B. Detailed microstructural investigations after laser metal deposition (LMD) including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) were performed. Results show that Si-alloyed claddings are single-phase with equiaxed grains of average sizes from ∼350 μm (1 at.% Si) decreasing with increasing Si content to ∼50 μm at 3 and 5 at.% Si. Contrary, the C-alloyed claddings microstructures are dendritic and ledeburite-like with perovskite-type carbides Fe3AlC0.6. The Ti- and B-alloyed cladding exhibits finely dispersed TiB2-type precipitations; at low contents in the sub-micron range and mainly present at the grain boundaries, at higher additions are quite large (3–5 μm) and present within individual grains. The individual hardphases, as quantified via nanoindentation, of Fe3AlC0.6-type carbides or TiB2-type borides exhibit average hardness values of ∼7.5 GPa and ∼ 45.5 GPa, respectively. Therefore, the hardness of C- and Ti & B-alloyed claddings increases from ∼260 HV10 (Fe3Al) to 405 HV10 (Fe3Al plus 5 at.% C) and to 340 HV10 (Fe3Al plus 3 at.% and 6 at.% B). The higher hardness of the C-alloyed cladding stems from the s higher hardphase content; the matrix hardness ranges between 4 and 5 GPa for all precipitation-strengthened claddings. Contrary, the Si-alloyed cladding exhibits a pronounced increase to 5.7 ± 0.8 GPa upon adding up to 5 at.% Si. Thus, an overall hardness of ∼350 HV10 is quantified on the expense of ductility (relaxation cracking after LMD). High-temperature hardness and scratch tests as well as wear investigations prove that the C- as well as Ti and B-alloyed claddings are superior to the plain Fe3Al and Si-alloyed ones, making them promising alternatives to other wear protection materials based on Co, Ni or Cr.

Influence of Si Addition on the Microstructures, Phase Assemblages and Properties in CoCrNi Medium-Entropy Alloy.

The effects of Si addition on the microstructures and properties of CoCrNi medium-entropy alloy (MEA) were systematically investigated. The CrCoNiSix MEA possesses a single face-centered cubic (FCC) phase when x is less than 0.3 and promotes solution strengthening, while the crystal structure shows a transition to the FCC+σ phase structure when x = 0.4 and the volume fraction of the σ phase increases with a microstructure evolution as the Si content increases. The Orowan mechanism from σ precipitation effectively enhances the strength, hardness, and stain hardening of CrCoNiSix MEA, which also exhibits superior hardness at high temperatures. Furthermore, a large amount of σ phase decreases the wear resistance because of the transformation of the main wear mechanism from abrasion wear for σ-free CrCoNiSix MEA to adhesion wear for σ-contained CrCoNiSix MEA. This work contributes to the understanding of the effect of Si addition on FCC structured alloys and provides guidance for the development of novel Si-doped alloys.

Spin reorientation in GdMn2(Ge1-xSix)2 compounds

Structure and magnetic properties of layered GdMn2(Ge1-xSix)2 (0 ≤ x ≤ 1) compounds were studied. All the compounds crystallize in the tetragonal ThCr2Si2-type structure. It was shown by magnetization measurements at low temperature on quasi-single crystals that, with increasing Si concentration, the easy magnetization direction reorients from the c-axis to the basal plane. The spin reorientation occurs via an angular phase. A model of three magnetic sublattices coupled by negative intersublattice exchange interactions was used to describe the field dependences of the magnetization. For GdMn2Ge2 and GdMn2(Ge0.9Si0.1)2 in the fields applied along the c-axis, seven different magnetic structures were predicted, including two angular structures considered for the first time. The model explains formation of angular magnetic structures in zero field in GdMn2(Ge1-xSix)2 system by taking into account magnetic anisotropy of Mn sublattices with a positive anisotropy constant K1 and negative K2.

Micro-Milling of Additively Manufactured Al-Si-Mg Aluminum Alloys.

Additively manufactured aluminum alloy parts attract extensive applications in various felids. To study the machinability of additively manufactured aluminum alloys, micro-milling experiments were conducted on the additively manufactured AlSi7Mg and AlSi10Mg. By comparing the machinability of Al-Si-Mg aluminum alloys with different Si content, the results show that due to the higher hardness of the AlSi10Mg, the cutting forces are higher than the AlSi7Mg by about 11.8% on average. Due to the increased Si content in additively manufactured Al-Si-Mg aluminum alloys, the surface roughness of AlSi10Mg is 26.9% higher than AlSi7Mg on average. The burr morphology of additively manufactured aluminum alloys in micro-milling can be divided into fence shape and branch shape, which are, respectively, formed by the plastic lateral flow and unseparated chips. The up-milling edge exhibits a greater burr width than the down-milling edge. Due to the better plasticity of AlSi7Mg, the burr width of the down-milling edge is 28.1% larger, and the burr width of the up-milling edge is 10.1% larger than the AlSi10Mg. This research can provide a guideline for the post-machining of additively manufactured aluminum alloys.

Physiology and transcriptomic analysis revealed the mechanism of silicon promoting cadmium accumulation in Sedum alfredii Hance

Silicon (Si) effectively promote the yield of many crops, mainly due to its ability to enhance plants resistance to stress. However, how Si helps hyperaccumulators to extract Cadmium (Cd) from soil has remained unclear. In this study, Sedum alfredii Hance (S. alfredii) was used as material to study how exogenous Si affected biomass, Cd accumulation, antioxidation, cell ultrastructure, subcellular distribution and changes in gene expression after Cd exposure. The study has shown that as Si concentration increases (1, 2 mM), the shoot biomass of plants increased by 33.1%–63.6%, the Cd accumulation increased by 31.9%–96.6%, and the chlorophyll, carotenoid content, photosynthetic gas exchange parameters significantly increased. Si reduced Pro and MDA, promoted the concentrations of SOD, CAT and POD to reduce antioxidant stress damage. In addition, Si promoted GSH and PC to chelate Cd in vacuoles, repaired damaged cell ultrastructure, improved the fixation of Cd and cell wall (especially in pectin), and reduced the toxic effects of Cd. Transcriptome analysis found that genes encoding Cd detoxification, Cd absorption and transport were up-regulated by Si supplying, including photosynthetic pathways (PSB, LHCB, PSA), antioxidant defense systems (CAT, APX, CSD, RBOH), cell wall biosynthesis such as pectinesterase (PME), chelation (GST, MT, NAS, GR), Cd absorption (Nramp3, Nramp5, ZNT) and Cd transport (HMA, PCR). Our result revealed the tentative mechanism of Si promotes Cd accumulation and enhances Cd tolerance in S. alfredii, and thereby provides a solid theoretical support for the practical use of Si fertilizer in phytoextraction.

Electronic structure and magnetic properties of Si doped AlFe2Ge full-Heusler

Using spin-polarized GGA combined with TB-mBJ approach and Monte Carlo simulation, we systematically explore the electronic and magnetic properties of cubic Al1-xSixFe2Ge (x = 0, 0.25, 0.50, 0.75, and 1) compounds. Structural optimization in the ferromagnetic and ferrimagnetic state proves that the AlFe2Ge alloy is ferrimagnetic with an enhanced lattice constant of 3.6075 Å. Elastic constants and related mechanical quantities such as bulk modulus B, Zener anisotropy factor A and Cauchy pressure Cp were calculated. The calculated total magnetic moments decrease with increasing Si concentration. The total magnetic moments of AlFe2Ge and SiFe2Ge compounds are fully compatible with the Slater-Pauling rule. The results show that the studied compound has remarkable properties such as high magnetic entropy at low temperature 40 J.kg−1.K−1, metallicity and ferrimagnetism. Noting that ferrimagnetic compound is more suitable for spintronic devices than the ferromagnetic compound due to its lower leakage fields and favorable robustness of magnetism.

Synergistic effects of chemical composition on precipitates, dislocations, and mechanical properties of precipitation-strengthened alloys

The properties of materials are intricately dependent on their chemical composition, and microstructures. Achieving a precise modulation in the composition and microstructure of materials to enhance properties significantly is a huge challenge. In this work, we uncovered the effects of nickel and silicon composition on the precipitates, dislocations, and properties of Cu–Ni–Si alloys. The results show that the volume fraction of precipitates increased from 0.84 % to 4.80 % with the increase of Ni and Si contents. The average diameter of the precipitates increased from 6.20 nm to 20.21 nm, and the dislocation density increased from 2.16 × 1013 m−2 to 4.08 × 1015 m−2 concerning the Ni and Si contents. In addition, the dislocation type changes from half-edge dislocation and half-screw dislocation to screw dislocation. The modified WHWA (Williamson Hall-Warren Averbach) method was proved to be the most accurate way of calculating dislocation density. As anisotropy was present in the alloy, adding a dislocation contrast factor and removing some lower-intensity diffraction peaks could further correct the obtained results and reduce the calculation error. Furthermore, the above analysis and findings were employed to design a Cu-3.21Ni-0.66Si alloy with a high yield strength (814 MPa), high ultimate tensile strength (970 MPa), and comparable electrical conductivity of 42.4 % IACS. This work offers a meaningful way to develop precipitation-strengthening alloys.