Increasing Al Content Research Articles

Effects of Al and V on deformation behavior and microscopic mechanism of titanium alloy at ultra-low temperature using molecular dynamics

Abstract A uniaxial tensile was executed with the molecular dynamics method, while the interaction between Ti, Al and V was described by hybrid potential. The influences of Al and V elements on the plastic deformation behavior and microscopic deformation mechanism of Ti-Al-V alloy were studied under ultra-low temperatures. The results show that the high content of Al and V elements leads to a sudden decrease of plasticity at 300 K. The plasticity is slightly reduced with increasing Al content when the content of V is 3.3~6.2 wt.% at 77 K. However, with the temperature reduced to 50 K, Al promotes the activation of dislocation when the content of V is high (6.2 wt.%) and hinders the activation of dislocation when V content is low (0.4 wt.%). At high V content (6.2 wt.%), the increase in plasticity with increasing Al content is more pronounced. Therefore, the strength and plasticity of Ti6.5Al6.2V increase with decreasing temperature.

Investigation of the influence of Al layer and total film thicknesses on structural and related magnetic properties in sputtered Ni/Al multilayer thin films

The effects of parameters of Al layer thickness and total film thickness on the structural and related magnetic properties of Ni/Al multilayer films were investigated. The films were deposited by a dual sputtering. The Ni content decreased gradually while the Al content increased as the Al layer thickness increased. It was also observed that the total film thickness had little effect on the film content. All films have a face-centred cubic structure. And, the surface morphology of Ni/Al films is more uniform and homogeneous than the surface of Ni film. For magnetic analysis, the properties were strongly changed with the parameters. The saturation magnetisation, Ms of Ni film was obtained as 572 emu/cm3 while the Ms of the Ni/Al films decreased from 441 to 298 emu/cm3 with increasing Al content in the films caused by the Al layer thickness. And, the increase of total film thickness resulted in a decrease of Ms value. While the coercivity, Hc value of the Ni film was 90 Oe, Hc of Ni/Al films was decreased to ~ 39 Oe with the formation of multilayer structure. Ni/Al multilayers were obtained magnetically softer than the Ni film. The Ms and Hc values were significantly affected by the variation of the film content and crystal structure caused by the changes in deposition parameters. Therefore, this is a fundamental step for Ni/Al multilayers to improve the properties of these films for their potential applications in microelectronic devices.

Tetrahedral Amorphous Carbon Coatings with Al Incorporation Deposited by a Hybrid Technique of Sputtering and Arc Evaporation

In this paper, tetrahedral amorphous carbon (ta-C) coatings containing Al were deposited by a hybrid technique of sputtering and arc evaporation. The influence of Al incorporation in the structure and properties of the ta-C coatings were studied as a function of the Al concentration. It is found that Al tends to form a Al-O-C bond when the Al concentration is small. An Al-C bond was detected when the Al concentration is high. Al can facilitate the graphitization of the ta-C coatings and the graphite cluster size as well as the sp2/sp3 ratio of the coatings increase as the Al concentration increases. The decline of the sp3 fraction causes the drop in the hardness of the coatings. The incorporation of Al can effectively decrease the residual stress of the ta-C coatings. During friction tests, Al can facilitate the formation of the sp2-rich graphitic tribo-layer and decrease the friction coefficient. Nevertheless, the decline of the hardness due to the Al incorporation will result in the increase in the wear rate of the coating. It is believed that the ta-C coating with a proper concentration of Al appears to achieve a good comprehensive performance with high hardness, low residual stress, and a low friction coefficient and wear rate.

The Effect of Nb Doping on the Properties of Ti-Al Intermetallic Compounds Using First-Principles Calculations.

The crystal structures, stability, mechanical properties and electronic structures of Nb-free and Nb-doped Ti-Al intermetallic compounds were investigated via first-principles calculations. Seven components and eleven crystal configurations were considered based on the phase diagram. The calculated results demonstrate that hP8-Ti3Al, tP4-TiAl, tP32-Ti3Al5, tI24-TiAl2, tI16-Ti5Al11, tI24-Ti2Al5, and tI32-TiAl3 are the most stable phases. Mechanical properties were estimated with the calculated elastic constants, as well as the bulk modulus, shear modulus, Young's modulus, Poisson's ratio and Pugh's ratio following the Voigt-Reuss-Hill scheme. As the Al content increases, the mechanical strength increases but the ductility decreases in the Ti-Al compounds. This results from the enhanced covalent bond formed by the continuously enhanced Al-sp hybrid orbitals and Ti-3d orbitals. Nb doping (~5 at.% in this study) keeps the thermodynamical and mechanical stability for the Ti-Al compounds, which exhibit slightly higher bulk modulus and better ductility. This is attributed to the fact that the Nb 4d orbitals locate near the Fermi level and interact with the Ti-3d and Al-3p orbitals, improving the metallic bonds based on the electronic structures.

Mechanical properties and water vapour corrosion behaviour of Al x CoCrFeNi high-entropy alloys.

Al x CoCrFeNi (x = 0.1, 0.5 and 1) high-entropy alloys (HEAs) were prepared using a spark plasma sintering (SPS) technique combined with aerosol powder. Their microstructure and phase constituents were characterized using an X-ray diffractometer and SEM, and their tensile properties, hardness and compactness were tested. The results show that the crystal structure of the Al x CoCrFeNi HEAs changed significantly with the Al content, from the original single face-centered cubic FCC phase (Al0.1CoCrFeNi) to an FCC + BCC structure (Al0.5CoCrFeNi), and then to FCC + BCC + sigma (σ) phase structures (AlCoCrFeNi). Chemical composition analysis showed that the crystal structure transformation was related to the segregation caused by the increased Al content. The hardness of the Al x CoCrFeNi HEAs increases with increasing Al content, and the hardness of AlCoCrFeNi reaches a maximum of 507.3 HV. The tensile properties of the alloy show a trend of first increasing and then decreasing with increasing Al content, and the yield strength, ultimate tensile strength and elongation of the Al0.5CoCrFeNi alloy reach maximum values of 527.4 MP, 943.3 MPa and 28.2%, respectively. The fracture mechanism of the Al0.1CoCrFeNi and Al0.5CoCrFeNi alloys is typical ductile fracture, while that of the AlCoCrFeNi alloy is cleavage fracture. The compactness of the alloy increases with the Al content. The samples were also subjected to high-temperature water vapour corrosion, and corrosion products such as Al3Fe5O12, CoCr2O4 and NiCr2O4 were found in the Al0.1 and Al0.5 alloys, whereas no oxide peaks were detected using XRD for the Al1 alloy. It was also presumed that a very thin alumina film was generated on the surface of the Al1 alloy, preventing the oxidation of the sample, in combination with the analysis of SEM, EDS and XPS behaviour.

First-principles study of the mechanical and thermodynamic properties of aluminium-doped magnesium alloys.

Magnesium-aluminum (Mg-Al) alloys are widely used in aerospace, automobile and medical equipment owing to their advantages of easy casting, high strength-to-mass ratio and good biocompatibility. The structural, mechanical, electronic and thermodynamic properties of MgxAly alloys (x + y = 16, x = 1, 2,…, 15) with varying Al-doping contents were studied using the first-principles method. In this work, the structures of MgxAly alloys were constructed by replacing Mg atoms in a supercell with Al atoms. The lattice parameters of the Al-doped MgxAly alloys decrease with an increasing Al content because of the smaller atomic size of Al than that of Mg. The calculated formation energies show that Mg11Al5, Mg5Al3 and Mg9Al7 have prominent structural stability. The analyses of the mechanical properties reveal that the doping of Al improves the ductility of MgxAly alloys. The elastic moduli increase with an increasing Al content, and Mg9Al7 has a notable ability to resist deformation, while Mg11Al5 and Mg5Al3 have better plasticity. The calculated results of their electronic properties reveal that Mg11Al5, Mg5Al3 and Mg9Al7 are good conductors without magnetism. Furthermore, CDD analyses show that the inner layer charges of Al atoms migrated to the outer layer, and the charges of Mg atoms accumulated significantly in the outer region of Al atoms. The Debye temperature of Mg9Al7 is higher than that of Mg11Al5 and Mg5Al3, indicating that it has better thermodynamic stability. Our findings would be helpful for the design of Mg-Al alloys with excellent mechanical and thermodynamic performances.

Simulation of displacement damage induced by protons incident on Al<sub><i>x</i></sub>Ga<sub>1<i>–x</i></sub>N materials

Gallium nitride materials, due to their excellent electrical properties and irradiation resistance, are expected to be used in future space electronics systems where electronic devices are composed of different amounts of Al<sub><i>x</i></sub>Ga<sub>1<i>–x</i></sub>N materials. However, most of their displacement damage studies currently focus on GaN materials, and less on Al<sub><i>x</i></sub>Ga<sub>1<i>–x</i></sub>N materials themselves. The mechanism of displacement damage induced by 10-keV to 300-MeV protons incident on Al<sub><i>x</i></sub>Ga<sub>1<i>–x</i></sub>N materials with different Al content is investigated by binary collision approximation method. The results show that the non-ionization energy loss of Al<sub><i>x</i></sub>Ga<sub>1<i>–x</i></sub>N material decreases with proton energy increasing. When the proton energy is lower than 40 MeV, the non-ionization energy loss becomes larger with the increase of Al content, while the trend is reversed when the proton energy increases. Analyzing the primary knock-on atoms and non-ionizing energy deposition caused by protons, it is found that the primary knock-on atoms’ spectra of different Al<sub><i>x</i></sub>Ga<sub>1<i>–x</i></sub>N materials are similar, but the higher the content of Al, the higher the proportion of the self primary knock-on atoms generated by elastic collisions is. For the non-ionizing energy deposition produced by protons at different depths, the energy deposition due to elastic collisions is largest at the end of the trajectory, while the energy deposition due to inelastic collisions is uniformly distributed in the front of the trajectory but decreases at the end of the trajectory. This study provides a good insight into the applications of GaN materials and devices in space radiation environment.

Study on the influence of al content on elevated temperature oxidation of MgF2 in HFP/air atmosphere

The influence of Al content on the high-temperature oxidation of MgF2 in an air/HFP atmosphere at temperatures ranging from 700 to 1000 °C has been studied with XRD and EDS. The results reveal that the addition of Al accelerated the oxidation of MgF2. With increasing Al content in MgF2, the oxidation of MgF2 was increased. At the same Al content, the oxidation of MgF2 also increased as the temperature rose. These results suggest that the increase of the Al content of MgF2 and the temperature decreased the high-temperature stability of MgF2.

Effect of Al Contents on Raman Spectra of MgSiO3 Perovskite

To study the effect of aluminum (Al) content on the vibration properties of MgSiO3 bridgmanites, we synthesized a series of aluminous bridgmanite at pressures of 23–27 GPa, a constant temperature of 2000 K in a multi-anvil apparatus. X-ray diffraction measurement confirms that they crystallized into a single-phase bridgmanite. With increasing Al contents, wavenumbers of Raman modes of bridgmanite did not show significant shifts. However, their full width of half maximum (FWHM) of Raman modes significantly became larger, suggesting that cation order and disorder may occur because of Al substitutions of Mg and Si cations in the bridgmanite structure.

Aluminum-based ceramic/metal composites with tailored thermal expansion fabricated by spark plasma sintering.

We have devised a moderate temperature spark plasma sintering route for preparing aluminum matrix composites which possess tailored coefficients of thermal expansion (CTEs) in combination with tunable electrical and thermal conductivities. Due to its isotropic negative thermal expansion over a wide temperature range, cubic-phase ZrW2-xMoxO8 (x = 0.0, 1.0) is an ideal secondary phase for metal matrix composites with suitable CTEs. In this study, high-density ZrW2O8/Al and ZrWMoO8/Al composites containing 30-70 vol% Al were fabricated using spark plasma sintering. X-ray diffraction analysis indicated that the composites were composed of a thermally-stable cubic phase at temperatures as high as 873 K for ZrW2O8 and 773 K for ZrWMoO8, without any orthorhombic high-pressure phase derived from the large thermal mismatch between the ceramic and metal during sintering. The thermal expansion curves of the ZrW2-xMoxO8/Al composites were consistent with the predictions made using the Rule-of-Mixtures. The CTEs could be controlled from negative to positive and even close to zero by simply varying the volume fraction of aluminum. Similarly, the thermal and electrical conductivity of the ZrW2-xMoxO8/Al composites increases with increasing Al content, which is thought to be mainly related to the contribution of the free electron conduction path of Al in the composites.

Effect of Al content on microstructure and mechanical properties of Alx(Nb3TaTi3Zr)100-x refractory high-entropy alloys

In this study, seven refractory high-entropy alloys of Al x (Nb3TaTi3Zr)100-x (x = 0, 5, 10, 15, 20, 25, 30) were synthesized by vacuum arc melting and characterized by various techniques, including XRD, SEM, EDS, compression tests at both 1200 °C and room temperature, as well as hardness tests. The analysis revealed that the alloys exhibit a single BCC structure when the Al content is between 0 and 15%, while the B2 phase appears at 20% and a mixed structure of BCC + B2 + σ phase at 30%. As the Al content increases, the hardness, stiffness, and room temperature yield strength of the alloy increases, while the plasticity decreases. Notably, the alloy with 25% Al content displayed the highest yield strength of 1400 MPa and Young’s modulus of 75.94 GPa at room temperature. Moreover, the hardness of the seven alloys increased from 247 HV to 490 HV with Al content from 0 to 30%. Furthermore, the alloy containing 30% Al exhibited a notable elevated-temperature yield strength of 143 MPa at 1200 °C.

Effects of Al addition on the microstructure and mechanical properties of AlxCoCrFeNi2.1 high-entropy alloys

To investigate the effect of Al content on the microstructure evolution and properties of AlxCoCrFeNi2.1 high-entropy alloys, the AlxCoCrFeNi2.1 high-entropy alloys (=0.5, 0.8, 1.0, 1.2 and 1.5) were prepared by vacuum arc melting. The results show that all the designed alloys are composed of single face-centered cubic (FCC) and ordered body-centered cubic (B2) phases. With the increase of Al content, the volume fraction of FCC phase decreases while that of B2 phase increases. In addition, the increasing Al content leads to the sequential increase of the hardness and yield strength of the alloys, while both the plasticity and compressive strength decrease. And the corresponding wear rate decreases from 312.9 × 10−5 mm2 N−1 to 55.3 × 10−5 mm2 N−1. It is revealed that the wear mechanism transforms from initially dominant abrasive wear with adhesive wear as a supplement to the mechanism dominated by adhesive wear with abrasive wear as a supplement, and finally to the oxidation wear plus abrasive wear. The experimental results show that the Al1.2CoCrFeNi2.1 alloy has the most excellent comprehensive performance, with an average hardness of 441 HV, compression ratio of 36.4%, compressive strength of 2618 MPa and wear rate of 68.0 × 10−5 mm2 N−1.

Tailoring microstructures and properties in Co-free FeNiCrCuAl high entropy alloys by Al addition

In this study, a series of Co-free FeNiCrCuAlx (x = 0.1, 0.3, 0.5, 0.8 and 1.0) high entropy alloys (HEAs) were developed by vacuum arc melting and casting method in high-purity argon atmosphere. The effects of Al addition on the microstructure and properties were investigated using X-ray diffraction, scanning electron microscopy, Vickers hardness tester, tensile test, wear test and electrochemical experiment. It was found that with the increase in the large atomic-sized Al content, the closely-packed FCC structure was destabilized for a transition to the loosely-packed BCC structure at x = 0.3. As x increased up to 1.0, the structure was mainly composed of BCC phase. The hardness of HEAs was enhanced by the influence of the contiguous atomic planes in BCC structures due to the relatively lower inter-planar spacing and higher lattice friction for dislocation motion, with the potential to increase the yield strength of the HEAs by 93.5 %. The friction coefficient decreased with increasing Al content, as indicated by stable profiles of Al0.8 and Al1.0 under progressive wear in comparison to those of Al0.1, Al0.3 and Al0.5 while the associated minimal wear depth and lower capacity for debris accumulation of the higher Al content HEAs confirmed their superior wear resistance. As FeNiCrCuAl0.5 presented the most superior corrosion resistance due to high resistance to ionic transport via the steady oxide film and the indication of a comparatively wider capacitive semicircle, undue Al additions would not be beneficial to improving plasticity or enhance corrosion resistance. Thus, FeNiCrCuAlx HEAs with Al contents in the range of 0.5–1.0 were found to possess optimized comprehensive properties, and can be suitably recommended as nuclear structural materials. This study will shed light on advancing the development of cutting-edge HEAs.

A functionally graded material from stainless steel 304 to Fe–40Al fabricated by dual wire arc additive manufacturing

In this study, gas tungsten arc welding (GTAW) based dual wire additive manufacturing (D-WAAM) is adopted to fabricate the functionally graded material (FGM) from stainless steel (SS) 304 to Fe–40Al, using SS 304 and aluminum alloy (AA) 1070 wires. The Al/Fe atomic ratio varies from 0 to 40 % by varying the ratio of the wire feed speeds of the SS and AA wires. The chemical composition, phases, microstructure, and mechanical properties of the FGM are investigated. The results showed that with the increase of Al content, microstructures evolve as follows: γ-Fe → γ-Fe + α-Fe → α-Fe → Fe3Al → FeAl. Cracks occur in FeAl region, caused by the high stress and the low plasticity. Dislocation walls prevent the large grains from slipping, leading to the loss of plasticity. The microhardness of SS 304 to Fe–40Al FGM ranges from 188HV0.5 to 558HV0.5. As Al content increases, the ultimate compressive strength decreases from 1820 MPa to 1061 MPa. The results on microstructure and mechanical properties provide guidance for the preparation of steel - aluminum alloy FGMs.

Low temperature dielectric studies of aluminum doped tin oxide nanoparticles

This study presents a facile sol-gel route for synthesizing pristine and Al-doped SnO2 nanoparticles. The phase purity of the synthesized nanoparticles was confirmed by powder X-ray diffraction (PXRD), revealing a tetragonal cassiterite structure for all samples. The crystallite size, determined by using the Scherrer equation and Willamson-Hall plot, ranged from 9.66 nm to 25.75 nm and exhibited an increasing trend with increasing doping concentration. Raman spectroscopy further corroborated this structural identification. The incorporation of aluminum (Al) into the tin oxide matrix was validated by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. UV–visible spectroscopy revealed a reduction in the bandgap from 3.6 eV to 3.2 eV upon Al doping, attributed to the decreasing lattice strain with increasing Al content and other underlying mechanisms. The dielectric properties, including dielectric constant, dielectric loss, and AC conductivity, were examined as a function of frequency and doping concentration within the temperature range of 100 K–400 K. These properties exhibited an increasing trend up to 6 % Al doping. Interestingly, the 8 % doped sample exhibited the lowest dielectric loss and the highest AC conductivity, making it a promising candidate for applications in high-frequency electronics, energy storage, and ferroelectric devices.

Evolution of microstructure and texture in Al-containing CoCrNi medium entropy alloys during severe warm-rolling

Al, as an alloying element, can influence the properties of the single-phase equiatomic CoCrNi MEA. In this study, different alloys of different Al concentrations added to CoCrNi MEA (AlxCoCrNi) were prepared by warm rolling to understand the effect of Al. The alloys were warm-rolled at 400 °C up to an 85% thickness reduction, followed by isochronal annealing at 700–1100 °C. The microstructure after deformation reveals the development of deformation heterogeneities such as shear bands and deformation nano-twins. The evolution of the weak brass component is seen after deformation. Different phases, such as BCC and sigma, evolve upon annealing treatment at different temperatures. The higher Al-content MEA (Al9.09) shows comparatively finer recrystallized microstructure irrespective of the annealing temperatures. Also, weak recrystallization texture develops after annealing, and the deformation texture components lying on α-fiber are preserved. This indicates the absence of preferential nucleation and growth during annealing. The hardness in the as-cast, deformed, and annealed conditions increases with increasing Al content, indicating the influence of Al in the strengthening of the AlxCoCrNi MEAs.

Phase evolution and mechanical properties of Ti1.5NbVAlx(x=0.25, 0.5, 0.75, 1) lightweight refractory medium-entropy alloys

A series of Ti1.5NbVAlx(x = 0.25, 0.5, 0.75 and 1) lightweight refractory medium-entropy alloys was synthesized through vacuum arc-melting, and the effects of Al addition on the phase types, microstructure and properties were investigated. Al0.25 alloy showed a single-phase BCC structure, and the increase in Al content induced a transition from disordered-BCC to ordered-B2, which caused short-range ordered strengthening. The relationship between Al content and ordered B2 was revealed by TEM. The mechanical properties of this alloy system were measured by compression and tensile tests and results indicated that Al0.25 and Al0.5 show excellent tensile strength (800, 857 MPa) even without any microstructural homogenization or optimization, meanwhile, the tensile ductility is 20 and 19 %. TEM observation demonstrates that multiple slip systems are activated in Al0.5 alloy and highly concentrated dislocation bands cross each other to form substructures, which has an important effect on the strength and elongation. Furthermore, the four alloys showed excellent compression plasticity, and the deformation was more than 50 % without fracture. When the Al content increased to 0.75, the maximum compressive yield strength σ0.2 = 1.29 GPa. This work is of great significance for the design of high specific yield strength and good ductility RH/MEAs.

Gallium and Germanium in Pennsylvanian Coals, Shales, and Paleosols in Indiana

Gallium (Ga) and germanium (Ge) are two elements of high industrial interest, included in the current United States and European Union lists of critical raw materials. This paper compares Ga and Ge concentrations between coals and associated paleosols and shales in Indiana. In addition, we include Ga and Ge data on the coal waste from coal preparation plants (coal tailings) to evaluate the coal tailings as potential sources of these elements. Paleosols have an average Ga content of 26.70 ppm, more than shales with an 18.77 ppm average, and coals with a 4.61 ppm average. The Springfield coal tailings average 15.60 ppm of Ga and the Brazil and Staunton Formation coal tailings average 31.90 ppm. For Ge, the coals have the highest average concentration (6.46 ppm), then shales (1.36 ppm), and paleosols (0.96 ppm). In coal tailings, the average Ge concentration is 13.90 ppm for the Springfield and 47.70 ppm for the Brazil and Staunton Formation coal waste. For Ga, a very strong positive correlation was obtained with aluminum (Al) in paleosols (R2=0.89) and coal tailings. A strong correlation was also obtained for shales (R2=0.86), together indicating that Al content is a great predictor of Ga concentrations in these materials. For Ge, there seems to be a tendency of decreasing Ge concentration with an increase in Al content in coals, suggesting an organic and not mineral association for this element. The organic association is also supported by a strong negative correlation between Ge and ash yield in coal tailings.

Effect of Al on microstructure and mechanical properties of HPDC Mg-6Y-3Zn alloys

The effect of Al on microstructure and mechanical properties is investigated in novel Mg-6Y-3Zn (WZ63) alloys produced by high-pressure die-casting (HPDC). The morphology of (Al,Zn)2Y phase varies from lamellar to flower-like and then to block shape with 0.4–1.0 wt% Al. The HPDC alloys exhibit fine grain sizes ranging from 4 μm to 7.4 μm, and significant grain refinement is obtained with Al as low as 0.4 wt%, which is different from that in gravity casting. The (Al,Zn)2Y phase is the crack source, and the dimple depth and elongation (EL) reduce with increasing Al content. Still, all the studied HPDC WZ63-xAl alloys maintain excellent tensile properties, keeping 256–274 MPa for tensile strength (UTS) and 7.4–9.7 % EL at room temperature and 188–213 MPa UTS and 10–35 % EL at 250 °C. Optimal mechanical properties are obtained with Al content around 0.4–0.5 wt%.

The effect of aluminium concentration on the resistance of Si3N4 to ion track formation

The role of Al impurities on the structural response of polycrystalline silicon nitride to swift Xe and Bi ions at single ion track and overlapped ion track fluences is investigated. Si3N4 with Al impurity concentrations of 3 at.%, 1 at.% and 0.1. at.% were examined by means of high resolution scanning transmission electron microscopy. The threshold electronic energy loss (Set) required to form amorphous tracks was found to decrease with increasing Al fraction from above 33 keV/nm (0.1 at.% Al) to below 22 keV/nm for specimens containing about 3 at.% Al. All specimens were partially amorphized at overlapping ion fluence and the amorphous fraction monotonically increased with increasing Al content at the same ion fluence.