Al Phase Research Articles

Properties of micro-arc oxidation coating of selective laser melting AlSi10Mg alloy

In this paper, micro-arc oxidation (MAO) coating is prepared on SLM AlSi10Mg alloy to improve its corrosion performance. The microstructure, composition, and electrochemical properties of the substrate and the coating at different oxidation times are analyzed. The results show that the MAO coating is mainly composed of Al, γ-Al2O3, α-Al2O3, and amorphous phases. At an oxidation time of 10 min, the coating achieves its maximum density. Additionally, the corrosion current density of the coating decreases by 5 orders of magnitude, the resistance value increases by 3 orders of magnitude, and the corrosion resistance is the best. Furthermore, the coating on the XY-plane exhibits better corrosion resistance compared to the coating on the XZ-plane.

How do reactive aluminum and iron phases control soil organic carbon and phosphate adsorption capacity in agricultural topsoils across Japan?

ABSTRACT The growing number of studies suggests that the prediction of soil organic carbon (SOC) storage and persistence can be improved by accounting for variations in soil reactive metal phases. Nevertheless, the dataset on reactive metals is often limited at a national scale. In Japan, the phosphate adsorption coefficient (PAC) has been measured for agricultural soils nationwide. PAC is known to be strongly controlled by reactive metals, and hence, it can be used as a surrogate for reactive metal content. However, the relationships between SOC, reactive metals and PAC across a wide range of agricultural soils remain unclear. We thus examined these relationships using agricultural topsoils taken from 115 sites across Japan, covering two major soil great groups, Andosols and Lowland soils, as well as various land uses and soil temperature regimes (7.2–19.1°C). For the whole dataset, PAC was strongly correlated with oxalate-extractable metals (Alox + 0.5Feox: Metalox, r = 0.83) and moderately with pyrophosphate-extractable metals (Alp + 0.5Fep: Metalp, r = 0.68). These results suggest a stronger contribution of short-range-order (SRO) minerals to PAC as the former parameter reflects the content of both SRO minerals and organically complexed metals, while the latter reflects only that of organo-metal complexes. Moreover, Metalp was the best predictor of SOC contents in both Andosols (r = 0.79) and Lowland soils (r = 0.65). When only soils at near neutral soil pH range were considered, the exchangeable Ca content also co-varied with SOC in Lowland soils (n = 17). Of the two metallic elements, reactive Al phases better explained the variation of SOC and PAC in Andosols, whereas reactive Fe phases also showed similar explanatory power for PAC in Lowland soils. Our analyses also suggested that soil group (esp. erosion intensity) and land use likely impacted the SOC-Metalox relationship in Andosols, whereas environmental factors such as soil temperature and soil redox regime affected those relationships in Lowland soils. Overall, we showed that PAC is a useful surrogate for SRO minerals and organo-metal complexes and, with careful considerations of the environmental and pedogenic factors, it is potentially useful to estimate the amounts of SOC stabilized by reactive metal phases in agricultural soils across Japan.

Microstructure and mechanical properties of CP780 steel - 7075 aluminum alloy laser welded joint assisted by rotating magnetic field

Abstract This study uses a rotating magnetic field for laser welding on 1 mm thick CP780 high-strength steel and 1.5 mm thick 7075 aluminum alloy. The effects of different welding parameters (B = 0 mT, B = 65 mT with V = 0°/s, B = 65 mT with V = 10°/s) on the morphology, microstructure, and tensile properties of welded joints are analyzed. At B = 0 mT, the weld shape is V-shaped, with the intermetallic compounds primarily consisting of needle-like brittle Al-rich (Fe, Si)Al2 phase and fewer granular ductile Fe-rich (Fe, Si)Al phase, resulting in poor mechanical properties. With the application of the rotating magnetic field, the laser energy becomes more concentrated, forming a ‘T’ shape weld. The rotating magnetic field (B = 65 mT with V = 10°/s) generates a constantly changing Lorentz force, promoting molten pool flow and enhancing Fe diffusion within the weld. This process reduces needle-like brittle Al-rich (Fe, Si)Al2 phase and increases granular ductile Fe-rich (Fe, Si)Al phase. It also accelerates the weld cooling rate and inhibits the reaction time and grain growth of intermetallic compounds, thereby reducing the thickness and content of the intermediate transition layer and significantly improving mechanical properties. A comprehensive comparison shows that the best mechanical properties are achieved at B = 65 mT with V = 10°/s. This study offers new insights and a theoretical foundation for achieving cost-effective, high-performance welded joints in advanced high-strength steel and high-strength aluminum alloy for automobiles, thereby facilitating lightweight vehicle development.

Section thickness effect on microstructure, mechanical and electrical properties of permanent steel mold cast eutectic Al-1.8Fe alloy

Abstract A eutectic aluminum alloy, with a composition of 1.8 wt% iron, underwent casting using permanent steel mold casting (PSMC) across three distinct section thicknesses: 2mm, 8mm, and 20mm. The microstructure of the as-cast alloy was analysed by the scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The microstructure analyses indicated that the cast Al-1.8Fe alloy consisted of the primary Al phase, eutectic Al phase, micron-sized eutectic Al-Fe phase, and nano-sized eutectic Al-Fe phase. The results of tensile testing revealed notable improvements in mechanical properties for the cast Al-1.8Fe alloy as the section thickness decreased from 20mm to 2mm. Specifically, Ultimate Tensile Strength (UTS), Yield Strength (YS), elongation (ef), modulus, toughness, resilience, and electrical conductivity increased from 85.99 MPa, 28.33 MPa, 15%, 63 GPa, 8.58 MJ/m3, 6.37 kJ/m3, 48.44 %IACS to 157.74 MPa, 84.83 MPa, 19%, 66.4 GPa, 23.87 MJ/3, 54.17 kJ/m3, 51.09 %IACS, respectively. Conversely, porosity levels decreased from 5.17% to 1.87% as thickness increased from 2mm to 20mm. The enhanced mechanical properties and electrical conductivity observed in the 2mm sample are attributed to its fine microstructure and low porosity. Additionally, SEM fractography revealed that fracture behavior in PSMC Al-1.8Fe was influenced by section thickness.

Quantitative pre-lithiation modulation of aluminum foil anode kinetics enables high rate and stable cycling of high-loading all-solid-state batteries

Aluminum (Al) foil holds great promise as a pure alloy anode for all-solid-state batteries (ASSBs) due to its suitable potential, high theoretical capacity, and excellent electronic conductivity. However, it remains challenging to achieve high reversibility and stability of the Al foil anode for ASSBs. Herein, we investigate the morphological and lithium (Li) kinetics evolutions of the Al foil anode paired with sulfide solid-state electrolyte (SSE). We identify that the significant reversible capacity loss stems from diminished Li kinetics at low Li contents (LixAl, 0 < x < 0.5), where the accumulation of pores and pure delithiated Al phase obstructs Li diffusion, increasing interfacial resistance and overpotential. Conversely, the Al foil anode with high Li contents (LixAl, 0.5 < x < 1) demonstrates reversible structures and rapid Li kinetics. Through precise pre-lithiation control, ASSBs with LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes exhibit outstanding rate capabilities and cycling stability, achieving over 4,000 cycles with 82.1 % capacity retention at 5C and demonstrating long-term cycling over 1,000 cycles with nearly 100 % capacity retention at ultra-high loadings. This work offers a viable strategy for advancing practical-level ASSBs with enhanced performance and longevity, contributing valuable insights to future battery technology.

Thermal and cyclic performance of aluminum alloy composite phase change microcapsules for high-temperature thermal energy storage

Al alloys are suitable for high-temperature applications such as solar thermal power generation and industrial heat utilization. However, addressing the challenges of high-temperature corrosion and material failure in Al alloys is of paramount importance. In practical industrial applications, there is a need to develop encapsulation techniques applicable to a wider range of Al alloy types and phase change temperature ranges, exploring the universality of the technology and the diversity of application scenarios. In this study, a dual encapsulation was conducted on binary and ternary Al alloys (including Al-Ni, Al-Mg, Al-Si-Mg, and Al-Mg-Zn). Aiming at thermal energy storage, four composite phase change microcapsules (CPCM) were successfully prepared and subjected to material characterization, thermal performance analysis, and thermal cyclic tests in air environments. After 2000 thermal cycles, no cracks were observed on the surface of the four CPCMs, and the microstructure remained intact. The components of the CPCMs maintained good chemical compatibility. Among the four types of CPCMs, the Al-Si-Mg CPCMs exhibited the best thermal cyclic stability, with a latent heat reduction rate of 19.5 % after 2000 cycles. The experimental results indicated that the dual encapsulation strategy was effective for various types of Al alloy PCMs, thereby expanding the application of Al alloys in high-temperature thermal storage. Furthermore, Al alloys with more regular morphology and lower active metal content exhibited better thermal performance and cyclic capability, making them more suitable candidates for high-temperature thermal storage applications.

Optimized EBSD-TEM method for the investigation of Al/Al2O3 interfacial orientation mismatch

The combined electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) method has been commonly applied to investigate material interfaces, from the perspectives of orientation and atomic structure. However, the loose combination is inadequate to capture some slight deviation from the ideal mismatch of interface, which limits an in-depth understanding of the interface. In this study, the combined EBSD-TEM method was systematically optimized and applied to investigate Al-Al2O3 heterogeneous nucleation interface. In this optimized EBSD-TEM method, the cylindrical equidistant projection was employed to illustrate the orientation mismatch relationship instead of the widely used pole figure. Lattice planes and directions from two phases are systematically presented in one figure, which provides a thorough perspective to identify all the potential matching features within the interface, meanwhile ensures a precise guidance for TEM sampling and observation. Such guidance is crucial for interface investigations, thereby this optimized EBSD-TEM method has great potential to be widely applied. Complex interface configurations of Al-Al2O3 interfaces were revealed, including the tilting of Al phase low-indexed planes relative to the interface and the deviations of matched lattice direction pairs between two phases. The complex interface configurations urge further development in the theory of nucleation interface mismatch.

Study on the effect of Sc and Zr addition on microstructure, mechanical property and fracture behavior of electron beam welded Be-Al alloys

Because of various excellent properties of low density, high specific strength and stiffness, high modulus, good thermal stability and corrosion-resistant, beryllium-aluminum (Be-Al) alloys have shown great potential to be used in nuclear industries. However, Be-Al alloys suffer from the bottlenecks of low solubility between Be and Al and the lack of effective technology for fabricating large-sized products. Herein, based on Sc and Zr addition, Be-Al-Sc-Zr alloys are successfully fabricated by conducting the electron beam welding (EBW) technology, and the effect of Sc and Zr addition on microstructure, mechanical property and fracture behavior of Be-Al-Sc-Zr alloys are studied. Microstructural characterizations show that both the EBWed Be-Al and Be-Al-Sc-Zr alloys exhibit two distinct zones of substrate zone (SZ) and fusion zone (FZ). Compared to grain size of the SZ and FZ in Be-Al alloys, grain sizes of these two zones in Be-Al-Sc-Zr alloys are significantly refined, thus leading to ultimate tensile strength (UTS) of the Be-Al-Sc-Zr alloys (∼176 MPa) approximately 150 % higher than that of the Be-Al alloys (∼118 MPa). Besides, a newly generated third phase (TP), which is confirmed as Be13(Scx, Zr1-x), forms within Al phase in both SZ and FZ of the Be-Al-Sc-Zr alloys. Different from fracture behavior of Be-Al alloys that preferentially fractures within Al phase or near the Be/Al interface, fracture of the Be-Al-Sc-Zr alloys is prone to occur within Be phase. As revealed by the calculation results of finite element method (FEM), the underlying mechanism for different fracture behaviors mainly ascribe to that the reinforcement of Al phase and existence of the newly formed TP can greatly increase the internal stress and even causes stress concentration within Be phase of the Be-Al-Sc-Zr alloys. The present findings may provide more insights to the micro-alloying and deformation mechanism of Be-Al alloys that with enhanced mechanical properties.

The Impact of Copper on the Mechanical Properties of Cast Motorcycle Cylinder Blocks

Enhancing the mechanical properties of cast products can be achieved by adding other elements. This research investigates the effect of copper (Cu) on the mechanical properties of cast motorcycle cylinder blocks, verified through microstructure analysis. Experiments were conducted by adding varying amounts of copper (Cu) at 5%, 10%, and 15%, with a casting temperature of 1010°C using a metal mold. Data collection included hardness testing, tensile strength testing, and microstructure analysis.The results showed that increasing the percentage of copper (Cu) in the cylinder block casting led to significant improvements in mechanical properties. The highest Vickers hardness was achieved with the addition of 15% Cu, measuring 229.23 HV. Similarly, the highest tensile strength was observed with the 15% Cu addition, reaching 104.218 MPa. Microstructure analysis revealed that the casting results predominantly consisted of α Al+θ (CuAl₂)+βSi phases, which were smaller compared to the α Al phase.

Enhanced mechanical and tribological properties of ultrasonically assisted stir-cast AA7075 metal matrix composites in challenging corrosive environments

Aluminum-based metal matrix composites (AMMCs) find extensive applications in aerospace, defence, automotive, and various sectors on account of remarkable mechanical properties, lightweight nature, and excellent dimensional stability. In this research, AA7075 matrix material was reinforced with tungsten carbide ceramic particles with various 0, 5, 10, 15 and 20 weight percentages (wt%) with the use of Ultrasonic assisted stir casing setup. The stir casted AA7075 MMCs were subjected to XRD, SEM, and density test to investigate the presence of elements, microstructure and density. The tensile, micro hardness, and wear test were performed on AL7075 based MMCs after conducting NaCl based spray test at the condition of spray pressure of 1.2 kg cm−2, spray duration of 120 h and PH value of 8.2 to determine the wear resistance, micro hardness and Ultimate Tensile Strength. The XRD test confirmed the presence of secondary phases such as Al2Cu, W2C, and MgZn2 with Al and WC phases. The SEM test confirmed the uniform dispersion and no more cluster formation upto 15 wt% WC addition and agglomeration of WC was occurred in the addition of 20 wt% of WC. The enhancing of wt% of WC improved the corrosion resistance, Micro hardness, UTS, wear and up to 15 wt% addition and decreases by the 20 wt% WC addition. The higher tensile strength 312 MPa was obtained from AA7075/15 wt%WC composite. The lower wear rate 0.11 mg m−1 was obtained from AA7075/15 wt%WC at 1000 m sliding distance with 1.2 m s−1 sliding velocity. The improved mechanical and tribological properties were mainly depended on strengthening mechanisms such as load transfer mechanism and dislocation strengthening mechanism.

The precipitation mechanism of the secondary phase in Inconel 617B alloy during ageing

ABSTRACT Precipitation of the secondary phase is a key factor that influences the strengthening effect of nickel-based superalloy. The precipitation behaviours of the M23C6 carbide and γ′-Ni3(Ti, Al) phase in Inconel 617B alloy aged at 700°C for different times were studied by scanning electron microscopy, transmission electron microscopy and atom probe tomography. Plate-like carbide nucleated in the interior of grain and irregular shape carbide precipitated at grain boundary respectively during the early stage of ageing. γ′ particle co-precipitated around carbide is a common microstructure feature during ageing for 5–160 h. After ageing for 160 h, γ′ phase is the main secondary phase. The carbide only distributes on the grain boundary, high density γ′ particle homogeneously distributes in the matrix after a longer ageing time. Elemental partitioning to the secondary phases and composition profiles across different phases was quantitatively analysed. Enrichments of Ti and Al at the carbide/γ interface are directly observed, which act as the nucleation site of γ′ particles during ageing. Enrichments of B, Si and Co at different interfaces are also detected. Based on the experimental results, the precipitation mechanisms of γ′ particles and carbide were discussed.

Association of rare earth elements with secondary mineral phases formed during alkalinization of acid mine drainage

Rare Earth Elements (REE) are present in acid mine drainage (AMD) in micromolar concentrations and AMD discharge may lead to an environmental risk. Alkaline Passive Treatment Systems (PTS) are often used to treat AMD and trap toxic trace elements. This study was set up to identify mechanisms by which REE are trapped in or on secondary phases formed in a PTS. Batch alkalinization experiments were performed to simulate PTS by sequentially increasing the pH of AMD collected from the Tharsis mining area inside the Iberian Pyrite Belt and synthetic AMD water samples via CaCO3 addition. The solids that precipitated up to pH ~4 and between pH 4–6 were collected and characterized by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) in combination with Scanning Electron Microscope/Energy Dispersive X-ray spectroscopy (SEM/EDX) and synchrotron-based X-ray Absorption Spectroscopy (XAS) and synchrotron-based Micro-X-ray Fluorescence (μ-XRF). Results reveal that REE are mostly scavenged between pH 4–6 in association with Al and Fe phases, whereas a smaller fraction is scavenged at pH ~4 by association with gypsum. Synchrotron-based analysis evidences the incorporation of La3+ into the gypsum structure by substituting Ca2+, indicating a co-precipitation mechanism with gypsum occurring mainly at low pH. Results from parallel adsorption and co-precipitation tests suggest that the REE scavenging between pH 4–6 could be due to a combination of adsorption and co-precipitation on Al(OH)3 and ferrihydrite. This implies that in PTS, REE would be mainly found in Al- (and Fe-) oxyhydroxides occurring in deeper layers of the PTS, i.e., where higher pH-values occur, though a small fraction, especially the light REE, could also be found incorporated into gypsum in the upper layers.

Investigation of the mechanical and durability properties of concrete containing modified fly ash and modified zeolite powder: An effective transport model for sulfate ions in concrete

The application of conventional fly ash and zeolite powder in the field of concrete durability is limited. In this study, durability tests coupling dry-wet cycling and sulfate erosion were conducted on concrete with varying dosages of modified fly ash (MFA) and modified zeolite powder (MZP). The compressive strength, failure mode, water absorption rate, and ion concentration changes were systematically investigated. The reaction products and structure were analyzed through SEM, EDS, and XRD tests, correlating with macroscopic parameters. An effective transport model for sulfate ions in concrete was established, considering the material influence coefficient km and the effective diffusion coefficient De. The results indicate that a higher content of Ca phases in MFA leads to a reduction in concrete early strength, while later stages exhibit rapid strength growth due to pozzolanic reactions. MZP contains a significant amount of Al and Si phases, which promote both early and later-stage concrete strength. MFA and MZP enhance the resistance of concrete to sulfate erosion, with MZP exhibiting a significantly superior improvement effect compared to MFA. This is attributed to the following factors: on the one hand, the addition of MFA and MZP reduces the porosity and improves the pore structure of concrete, thus delaying the diffusion of sulfate ions into the concrete; on the other hand, the pozzolanic reactions of MFA and MZP consume available calcium hydroxide, leading to the formation of C–S–H and C-A-S-H gels, which densify the microstructure and reduce the probability of leaching erosion of hydration products, thereby limiting the formation of ettringite. The applicability and reliability of the sulfate-ion effective transport model were verified based on experimental data. The model can be employed to predict the distribution of sulfate ions in different types of concrete under various erosion durations, reducing workload and providing a theoretical basis for the durability design and service life prediction of concrete structures in sulfate environments.

Influence of the Nb–Al ratio on homogenization behavior and hierarchical microstructures in high-entropy superalloys

In this investigation, we explore the impact of the Nb–Al ratio on the microstructural and mechanical properties of high-entropy superalloys (HESAs), focusing on hierarchical microstructures. Utilizing a series of HESAs with varying Nb–Al ratios, our study employs advanced characterization techniques, including differential scanning calorimetry (DSC) for thermal analysis, electron probe micro-analyzer (EPMA) for compositional analysis for the design of a homogenization treatment at 1500 K/24 h. Transmission electron microscopy (TEM) reveals that the increasing Nb–Al ratio refines the γ' precipitates and influences the size and volume fraction of embedded hierarchical γ particles. ThermoCalc equilibrium phase analysis and Vegard's-law calculations reveal a minimal lattice misfit between these phases, highlighting the interplay between Nb–Al ratio and phase stability. The increasing Nb–Al ratio inhibits the formation of hierarchical γ particles. We observe an enhancement in hardness from 433 HV to 492 HV with an increasing Nb–Al ratio. This study provides valuable insights into the role of Nb and the Nb–Al ratio in HESAs with hierarchical microstructures, demonstrating its significant influence on γ particle formation within γ' precipitates and mechanical strength. The findings advance our understanding of alloy design and pave the way for developing advanced HESAs for high-temperature applications.

Microstructure evolution during solidification in a low superheat casting process of the Al-Mg2Si composites having excess Si: A phase field study

A two-dimensional phase field (PF) model of solidification during low superheat casting has been developed to grab insight into the microstructure formation mechanism of the Al-xMg2Si-ySi composite, having extra Si as the grain refining agent. The developed PF model employs a seed undercooling based nucleation model to simulate the formation of primary Mg2Si and α-Al grains, wherein the interfacial energy of the Al-melt interface is taken from literature, and a Molecular Dynamics (MD) model is employed to calculate the interfacial energy of the Mg2Si-melt interface. The simulation study predicts the microstructural parameters such as grain size, and sphericity of the primary Al and primary Mg2Si phases, as well identifies the appropriate numerical parameters such as mobility, anisotropy parameters to study the microstructure evolution in the Al-xMg2Si-ySi composites. The kinetics of grain growth of both α-Al and primary Mg2Si have been studied. Novelty of the study lies in developing a near-accurate PF model capable of optimising the weight fraction of Mg2Si and excess Si in the low superheat cast Al-xMg2Si-ySi composite system, in view of obtaining the lower grain size and higher sphericity of both primary Al and primary Mg2Si grains, which is in line with the experimental observations. The proposed PF model is capable of predicting the faceted growth of Mg2Si particles in the Al-xMg2Si-ySi composite, in presence of extra Si and during low superheat casting, and the dendritic growth of Mg2Si in the binary Al-Mg2Si composite having high Mg2Si weight fraction. Following the Jackson’s model of interface growth, it has been demonstrated that the modification of kinetic coefficient leads to a transformation of morphology of Mg2Si particles from large dendritic to faceted ones.

First-principles prediction of the Co–Al phase diagram including configurational, vibrational and magnetic contributions

Co-based superalloys have attracted attention to replace Ni-based superalloys in high temperature structural applications because of their higher melting temperature and corrosion resistance. Strengthening is provided by Co3(Al, X) (X = W, Cr, Mo, Ni) phases and optimization of their properties requires detailed information about the free energies of the different phases and of the phase diagram of the Co–Al system. This is achieved in this paper through first principles calculations in combination with statistical mechanics. Configurational entropic contributions to the free energy were included through Monte Carlo simulations using the cluster expansion formalism. The vibrational entropy of each phase was determined through the length-stiffness relationship while the magnetic entropy was also included through the Heisenberg Hamiltonian. The computed phase diagram is compared with the currently accepted experimental phase diagram and the different contributions to the stability of each phase are analyzed independently. The potential of this strategy to predict phase diagrams of magnetic systems is clearly established.

Transient thermal 2D FEM analysis of SiC MOSFET in short-circuit operation including high-temperature material laws and phase transition of aluminum source electrode

Understanding the electrothermal behavior of SiC MOSFET power devices under extreme operation conditions, such as short circuits, is crucial for their application certification. However, simulating short circuits in electronic components is challenging due to the necessity of a comprehensive thermal and electrical Multiphysics model that incorporates material laws and respects elevated temperatures with broad ranges. It is also needed to model the melting of the topside Al electrode. The paper presents for the first time a 2D electrothermal FEM that simulates the thermodynamic behavior of SiC MOSFET at high temperatures transistors under short-circuit conditions, including wide-range temperature-dependent material property laws. This work models the Al phase transition by considering the apparent heat capacity method and including the latent heat absorbed during the Al solid-liquid phase change (PC). The geometric accuracy of this study provides significant added values compared to existing 1D models. It was deduced that including the temperature-dependent material laws highly impacted the results. The rise in SiC junction temperature led to a delay in the onset of Al melting. It also impacted the progression manner of the Al melting process after the formation of new melting fronts.

Fabrication of Pt modified aluminide diffusion coatings on Ti6Al4V alloy and their oxidation behaviors

PtAl2 + TiAl3, β-(Ni,Pt)Al + TiAl3 and β-(Ni,Pt)Al + PtAl2 + TiAl3 coatings were prepared on Ti6Al4V alloy substrates by pre-depositing a Ni/Pt layer prior to aluminizing. It was found that a single pre-deposited Pt layer tended to form PtAl2 phase and a Ni + Pt layer favored to form β-(Ni,Pt)Al phase during aluminizing. After thermal cycling, the PtAl2 + TiAl3 coating formed a dense Al2O3 scale and showed least weight gain and thickness increase. For the β-type coatings, their oxidation product contained porous TiO2. The results indicate that the PtAl2 + TiAl3 coating could block the out-diffusion and oxidation of Ti.

Phase Relations of the Sm–Ni–Al Ternary System at 800 °C in the 30–100 at.% Al Region

The Sm–Ni–Al phase relationships at 800 °C have been investigated by using several well–focused experimental techniques such as X–Ray Powder Diffraction (XRPD), Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Microprobe Analysis (EPMA). The isothermal section of the Sm–Ni–Al system at 800 °C was constructed according to the present experimental results. More than 50 alloys have been synthesized and characterized in the 30–100 at.% Al region. At 800 °C, 9 intermetallic phases have been confirmed, characterized and their relationships have been established. In the Al-rich corner, the presence of two ternary invariant reactions have been postulated whilst along the 16.67 at.% Sm isopleth, the presence of two structurally related extended solid solutions have been observed. The determined phase equilibria at 800 °C are discussed and compared with the isothermal section at 500 °C already reported in literature.

Compositionally graded titanium to aluminum processed by laser powder bed fusion process: Microstructure evolution and mechanical properties

A compositionally graded Ti–Al alloy with a designed composition range from pure Ti to pure Al was successfully produced by a laser powder bed fusion (L-PBF) system equipped with two powder feeders. The compositionally graded Ti–Al profile is confirmed by scanning electron microscopy, X-ray diffraction analysis, electron backscatter diffraction microscopy, and transmission microscopy. The graded material is free of macro-horizontal cracks, but micro-cracks appear at the center of the sample. Varying the Ti and Al ratio along the build direction induces microstructural changes, transforming α+β-Ti into solid solution, creating intermetallics (Ti and Al), and yielding an Al phase with diverse morphologies. Additionally, the Ti–Al ratio's influence on microstructure formation and phase evolution results in varying mechanical properties among the graded material's layers. The results demonstrate that the L-PBF process can achieve continuous compositional grading of Ti–Al materials in a single run. Moreover, this study hold the potential to facilitate the design and production of numerous compositional variants for high entropy alloys and multi-materials, enabling future investigation into microstructural evolution, phase transformation, and physical and mechanical properties.