Dissolution Of Phase Research Articles

Study on the investigation of creep behaviour in squeeze cast Ca-modified AZ91 magnesium alloy

ABSTRACT The AZ91 (Mg-Al) alloy is the most commonly used Mg-cast alloy with high specific strength and excellent die-castability; however, its poor creep performance limits its applications at elevated temperatures. In the present investigation, the effect of Ca addition on the microstructure development and creep performance of squeeze-cast AZ91 alloy recognised as AZX911 alloy has been investigated at 150°C–250°C temperature under 65 and 80 MPa stress. The addition of Ca in the AZ91 alloy results in the precipitation of the thermally stable Al2Ca intermetallic phase, which partially suppresses the precipitation of the thermally unstable β-Mg17Al12 phase and significantly improves the creep resistance of the AZ91 Mg alloy. The governing creep mechanism of AZX911 alloy is found to follow power law creep with n = 3.49 at 150°C that mainly results from dislocation climb. In contrast, a transition to power-law breakdown is observed at 175°C. The resistance to creep deformation of AZX911 further improves with heat treatment at 450°C as compared to the as-cast specimen of the same alloy due to the complete dissolution of the β-Mg17Al12 phase. The activation energy of phase dissolution, estimated using the Kissinger method, is found to be higher (923 kJ/mol) for the Al2Ca intermetallic phase as compared to that for β-Mg17Al12 phase (664 kJ/mol) in AZX911 alloy.

The evolution and dissolution mechanism of θ-Al2Cu phase and the analysis of precipitation of a novel AlCu phase during elevated aging

The evolution and dissolution mechanism of the θ-Al2Cu precipitates were investigated in this study by transmission electron microscopy (TEM) during the re-aging at high temperatures for a long time. The results advance the current knowledge of dissolution and its associated mechanisms of the θ-Al2Cu phase in AlCu alloys. In this study, the coarsening and dissolution of θ-Al2Cu phase in T6 heat-treated Al4Cu alloy during various times (0−1000h) of re-aging temperature 420 °C were studied experimentally and theoretically. The morphological characterization revealed that the θ-Al2Cu phases gradually increase in size and decrease in volume density during the aging process, which can be attributed to coarsening and dissolution phenomena occurring during re-aging. Additionally, a body-centered tetragonal AlCu phase is precipitated within the θ-Al2Cu phase during the high temperature re-aging process, which is a characteristic of this phase prior to dissolution. Moreover, the primary mechanisms responsible for the high temperature melting of the θ-Al2Cu phase are the formation of the AlCu phase and the initial melting of the Cu-poor region in the θ-Al2Cu phase. The Cu atoms in θ-Al2Cu phase dissolve and diffuse into the Al matrix, forming L12 ordered AlCu solute clusters through long-range diffusion.

Self-Etching Ceramic Primer Affects Surface Topography and Roughness of Two Zirconia-Reinforced Lithium Silicate Ceramics.

This article evaluates the etching efficacy of a self-etching ceramic primer (SECP) on zirconia-reinforced lithium silicate (ZLS) ceramics. Celtra Duo (DeguDent GmbH, Hanau-Wolfgang, Germany) and Vita Suprinity (Vita Zahnfabrik, Bad Säckingen, Germany) were used in this study. A total of 36 ceramic slices were prepared from each ceramic material and randomly distributed into three groups according to the surface treatment applied (n = 12 per group). Group 1 (polished) was polished with silicon carbide paper discs and did not undergo any surface treatment; group 2 (SECP) was surface treated with SECP (Monobond Etch and Prime, Ivoclar Vivadent, Schaan, Liechtenstein); group 3 (hydrofluoric acid [HF]) was surface treated with 4.7% HF etching. Half of the specimens (n = 6) from each group were gold-sputtered, and the surface topographic alterations were evaluated by scanning electron microscopy at magnifications of 5,000× and 10,000 × . The surface roughness of the other half (n = 6) from each group was tested using a three-dimensional optical profiler. Data were statistically analyzed using two-way analysis of variance and Tukey's multiple comparisons test. Both SECP and HF etching surface treatments resulted in a statistically significant increase (p < 0.05) in the surface roughness of both ceramic materials, compared to that of their respective control group specimens (polished). HF etching resulted in a significant dissolution of the glassy phase of each ceramic. SECP can effectively etch ZLS ceramics. The etching patterns created after the application of SECP were mild compared to those produced by HF etching. The topographic surface features of ceramics are affected by both, surface treatment and material composition.

Osteogenic Potential and Long-Term Enzymatic Biodegradation of PHB-based Scaffolds with Composite Magnetic Nanofillers in a Magnetic Field.

Millions of people worldwide suffer from musculoskeletal damage, thus using the largest proportion of rehabilitation services. The limited self-regenerative capacity of bone and cartilage tissues necessitates the development of functional biomaterials. Magnetoactive materials are a promising solution due to clinical safety and deep tissue penetration of magnetic fields (MFs) without attenuation and tissue heating. Herein, electrospun microfibrous scaffolds were developed based on piezoelectric poly(3-hydroxybutyrate) (PHB) and composite magnetic nanofillers [magnetite with graphene oxide (GO) or reduced GO]. The scaffolds' morphology, structure, mechanical properties, surface potential, and piezoelectric response were systematically investigated. Furthermore, a complex mechanism of enzymatic biodegradation of these scaffolds is proposed that involves (i) a release of polymer crystallites, (ii) crystallization of the amorphous phase, and (iii) dissolution of the amorphous phase. Incorporation of Fe3O4, Fe3O4-GO, or Fe3O4-rGO accelerated the biodegradation of PHB scaffolds owing to pores on the surface of composite fibers and the enlarged content of polymer amorphous phase in the composite scaffolds. Six-month biodegradation caused a reduction in surface potential (1.5-fold) and in a vertical piezoresponse (3.5-fold) of the Fe3O4-GO scaffold because of a decrease in the PHB β-phase content. In vitro assays in the absence of an MF showed a significantly more pronounced mesenchymal stem cell proliferation on composite magnetic scaffolds compared to the neat scaffold, whereas in an MF (68 mT, 0.67 Hz), cell proliferation was not statistically significantly different when all the studied scaffolds were compared. The PHB/Fe3O4-GO scaffold was implanted into femur bone defects in rats, resulting in successful bone repair after nonperiodic magnetic stimulation (200 mT, 0.04 Hz) owing to a synergetic influence of increased surface roughness, the presence of hydrophilic groups near the surface, and magnetoelectric and magnetomechanical effects of the material.

Enhancing mechanical properties in Ti-Containing FeMn40Co10Cr10C0.5 High-Entropy alloy through Chi (χ) phase dissolution and precipitation hardening

This research investigates the effects of adding 2 at.% Ti on the microstructure, phase transformation, and mechanical properties of FeMn40Co10Cr10C0.5 high-entropy alloy (HEA) in both as-cast and homogenized conditions. The incorporation of Ti increased the lattice parameter of the FCC matrix and caused greater lattice distortion (∼5.9 %) due to the larger atomic radius of Ti. The negative mixing enthalpy of Ti resulted in segregation at interdendritic regions, forming a Ti-rich Chi (χ) phase during solidification. The as-cast structure displayed a dendritic microstructure consisting of 77.9 % FCC, 20.6 % χ, and 1.5 % TiC phases. After homogenization at 1200 °C for 2 h, the χ phase was dissolved, increasing the volume fraction of TiC to 24 %. The homogenized sample exhibited a substantial improvement in tensile properties, i.e., with the ultimate tensile strength (UTS) rising from 631 MPa in the as-cast condition to 689 MPa, and yield strength (YS) increasing from 346 MPa to 419 MPa, while maintaining an elongation of ∼ 54 %. These enhancements are attributed to solid solution strengthening, increased carbide precipitation, and the dissolution of the χ phase into the FCC matrix.

A high-performance TRIP Mg-Sc-Zn alloy enhanced by fine grain strengthening and nano-precipitate strengthening

The Mg–Sc alloys have attracted considerable attention from researchers due to their martensitic transformation behavior. However, the relatively low yield strength limits their practical application. Thus, Zn alloying combined with annealing treatment was used to improve the mechanical properties by modulating its microstructure. Zn alloying can effectively delay the recrystallization rate and refine the grain size of the alloy. The β/α intensity ratio and grain size of β phase increase with the increasing annealing temperature. When the annealing temperature is 600 °C, the major phase is β-Mg-Sc with minor α-Mg-Sc, ScZn and Mg3Sc phases. Further increasing the temperature to 650 °C would lead to the dissolution of ScZn and Mg3Sc phases into the matrix, resulting in smaller precipitations. The Mg-Sc-Zn alloy annealed at 600 °C for 60 min owns the best comprehensive mechanical properties, with yield strength, ultimate tensile strength, and elongation of 307.2 MPa, 330.5 MPa, and 21.1%, respectively. Further TEM analysis reveals that fine grain reinforcement, precipitation reinforcement, and stress-induced martensitic transformation during tensile deformation are the main factors for the enhancement of strength and ductility in this alloy.

Eutectic mixtures of nevirapine: Phase diagrams, solid-state characterization, and dissolution studies

Solid-state modifications can improve drug performance. Studies have shown that multicomponent crystals, such as cocrystals and eutectic compositions, have successfully improved the performance of certain drugs, including their solubility. Nevirapine (NEV) is an antiretroviral drug with low aqueous solubility, impacting its bioavailability. This work aimed to study different nevirapine/co-former solid eutectic systems, define their phase diagrams and evaluate their dissolution properties. Caffeine (CAF), Theobromine (TEOB), and Theophylline (THEO) were chosen as co-formers due to their functional groups that can interact with NEV. Aiming to determine both temperature and eutectic composition, phase and Tamman diagrams were obtained using the differential scanning calorimetry (DSC) analysis of the mixtures indifferent NEV-co-former compositions (%w/w). Powder X-ray diffraction (PXRD) and DSC were used to characterize the eutectic materials. To assess the influence of eutectic systems on dissolution properties, we determined the powder dissolution profiles and intrinsic dissolution rates of anhydrous NEV and eutectic systems NEV-CAF and NEV-THEO using different dissolution media (pH 1.2 and pH 6.8). The eutectic compositions were calculated through the phase diagrams, interpolating the curves obtained by linear regression. Thus, the eutectic composition of the NEV-CAF system was determined to be 36.55 % NEV and eutectic temperature at 201.1 °C, while in the NEV-THEO system, the eutectic was obtained in a composition of 71.04 % NEV and eutectic temperature at 217.8 °C. Tamman diagrams were generated using the enthalpy values obtained from the DSC curves, and eutectic compositions were calculated using linear regression. The analysis revealed a eutectic composition of 36.51 % of NEV for the NEV-CAF system, and a eutectic composition of 70.94 % of NEV for the NEV-THEO system. It was not possible to determine the eutectic mass fraction of NEV-TEOB. A comparison of dissolution profiles and intrinsic dissolution rates in different dissolution media showed a significant improvement in the NEV dissolution rate in both eutectic systems. In an acidic medium, NEV dissolved 16 times faster in the NEV-CAF sample and 4 times faster in the NEV-THEO sample compared to pure anhydrous NEV. In a neutral medium, the dissolution profile of NEV was even more favorable in the same eutectic systems, showing that the increase in dissolution is relevant in a wide range of pH. In addition, the intrinsic dissolution rate in the two eutectic systems was higher than that of anhydrous NEV in all employed dissolution mediums. These eutectic systems improve the dissolution rate compared to pure NEV, offering the potential for enhancing the dissolution of poorly water-soluble drugs in the future.

Wettability-dependent dissolution dynamics of oxygen bubbles on Ti64 substrates

In this study, the dissolution of a single oxygen bubble on a solid surface, here Titanium alloy Ti64, in ultrapure water with different oxygen undersaturation levels is investigated. For that purpose, a combination of shadowgraph technique and planar laser-induced fluorescence is used to measure simultaneously the changes in bubble geometry and in the dissolved oxygen concentration around the bubble. Two different wettabilities of the Ti64 surface are adjusted by using plasma-enhanced chemical vapor deposition. The dissolution process on the solid surface involves two distinct phases, namely bouncing of the oxygen bubble at the Ti64 surface and the subsequent dissolution of the bubble, primarily by diffusion. By investigating the features of oxygen bubbles bouncing, it was found that the boundary layer of dissolved oxygen surrounding the bubble surface is redistributed by the vortices emerging during bouncing. This establishes the initial conditions for the subsequent second dissolution phase of the oxygen bubbles on the Ti64 surfaces. In this phase, the mass transfer of O2 proceeds non-homogeneously across the bubble surface, leading to an oxygen accumulation close to the Ti64 surface. We further show that the main factor influencing the differences in the dynamics of O2 bubble dissolution is the variation in the surface area of the bubbles available for mass transfer, which is determined by the substrate wettability. As a result, dissolution proceeds faster at the hydrophilic Ti64 surface due to the smaller contact angle, which provokes a larger surface area.

Corrosion resistance of pressure/pressureless sintered cemented carbides with/without graphene oxide in NaOH solution

The electrochemical corrosion performance of WC-Co hard alloy was studied under pressure/pressureless sintering and conditions with/without graphene oxide added. Three electrochemical testing methods were used to evaluate the corrosion behavior: open circuit potential, electrochemical impedance spectroscopy, and dynamic potential polarization. The corrosion resistance of the alloy was compared using three parameters of corrosion potential, corrosion current density, and total impedance. The corrosion mechanism was studied by observing the surface morphology of corroded alloy using scanning electron microscopy and analyzing the surface corrosion products using X-ray photoelectron spectroscopy. The results showed that pseudo-passivation phenomenon appeared in the potentiodynamic polarization curve of the hard alloy in the sodium hydroxide solution. The corrosion behavior was mainly controlled by anodic dissolution, with the dissolution of WC phase being greater than that of Co phase. The corrosion resistant properties of the pressure sintered cemented carbide are higher than that of the pressure-less sintered cemented carbide respectively in NaOH solution, mainly because pressure increases the grain size and decreases the grain boundaries of cemented carbide, which can be regarded as the dislocation wall between grains and normally attacked by the serious corrosion preferentially.

Revealing the hydration mechanisms in iron-rich calcium sulfoaluminate cements with elevated bauxite residue content

The goal of the study was to investigate the reactivity at different Blaine, hydration behavior, and performance of calcium sulfoaluminate-ferrite cement (CSA-F). The raw meal incorporated bauxite residue (38 wt%) fired at 1260 °C and 1300 °C for 30 and 60 minutes. Based on multi-objective optimization, an optimum dosage of citric acid ranges between 0.4<x<0.6 wt% with a w/b ratio of 0.45 was chosen for the mortar evaluation and hydration studies. At an early age, monosulfates-AFm only started appearing for 1300_30. In the later age, an increase in ettringite formation was only reported at 1300°C for 60 min due to the dissolution of the Ternesite phase after 7d of hydration. Later-age studies after 28d reported ettringite, monosulfates, hydrogarnets (except for 1300_60), and strätlingite had formed. The 28d highest compressive strength was reported for 1300_60 corresponding to the highest bound water and amorphous content from the pore filling ettringite and amorphous stratlingite.

Microstructural evolution and dynamic mechanical behavior of PM 2195 Al-Li alloy with resistance to shear instability in high strain rate deformation

The risk of adiabatic shear instability is common in traditional alloys covering high-strength steels, copper alloys and aluminum alloys during high strain rate deformation. However, the research on shear instability of 2195 Al-Li alloy prepared by powder metallurgy (PM) at high strain rates is still blank. The purpose is to explore its microstructure evolution and dynamic compression behavior. In this work, the 2195 Al-Li alloy prepared by PM amazingly demonstrates excellent resistance to shear instability at high strain rates during Split-Hopkinson pressure bar (SHPB) experiment. The microstructural evolution of grains and T1 (Al2CuLi) precipitate phase, and dynamic compression behavior of PM 2195 Al-Li alloy at various strain rates from 3000 s−1 to 9000 s−1 are investigated in detail employing correlative electron-backscatter diffraction (EBSD) and transmission electron microscopy (TEM). During high strain rate deformation, the alloy undergoes grain fragmentation and rotation, increasing dislocation density around the grains. When the strain rate is from 3000 s−1 to 7500 s−1, the Kernel Average Misorientation (KAM) value increases, indicating intensified localized strain. At a strain rate of 9000 s−1, a small number of grains are surrounded by nanocrystals (around 200 nm) that undergo stress release, while the average size of micrometer-sized grains is 0.81 μm. As the strain rate increases, the T1 phases in the alloy extends, vibrates, and fractures before dissolving in the matrix, while high-rate deformation promotes dislocation entanglement and defects, leading to the decomposition or ordering of precipitated phases through rapid plastic deformation. By virtue of energy dissipation strategy via the formation of nanocrystallines and dislocation behavior induced by the dissolution of T1 phases, the "positive-positive" effect is observed. The PM 2195 Al-Li alloy undergoes no shear failure even at the strain rate of 9000 s−1, showing great prospects in future applications in dynamic-loading conditions.

Leaching and geochemical modeling of asbestos-cement waste and mine asbestos

Asbestos-Containing Materials (ACMs) were widely used in the construction sector but, due to their harmful health effects, many countries have banned their use. ACMs are classified as hazardous and, in contact with water, produce potentially harmful leachates. The objective of this work was to determine the leaching behavior of 20 elements from two asbestos-cement materials and mine asbestos samples across the entire pH range and varying liquid-to-solid ratios (column tests). The pH-dependence tests showed consistent leaching patterns across the three materials. Geochemical speciation model (LeachXS) predictions were successful in most cases of the batch experiments and were improved by adjusting iron oxides concentration for some elements. Model predictions were successful for fewer elements in the column experiments. Depending on the pH, element release was controlled by respective solid phase dissolution, sorption onto iron oxides and substitution in ettringite. Some leaching concentrations exceeded the EU limits for granular non-hazardous waste landfills. Considering the strongly alkaline nature of monolithic asbestos-cement waste undergoing carbonation, we propose all three materials to be disposed of in non-hazardous waste landfills, according to EU legislation. A case study concluded that geochemical modeling of ACMs leaching is a useful tool in estimating element release under various environmental conditions.

Investigation on electrochemical corrosion behavior of Cu-14Fe -(0, 0.05)Ce alloys

This work thoroughly investigated the electrochemical corrosion behaviors of Cu-14Fe-(0, 0.05) Ce alloys. Experimental findings revealed that the addition of Ce did not change the phase constituent, but refined α-Fe phase particle from 0.30 ± 0.04 to 0.22 ± 0.03 μm and increased its content from 1.24% to 2.17%. With the increase of corrosion time, adding Ce could increase the linear polarization resistance by up to 3 times, and correspondingly the corrosion rate was reduced to half. Moreover, Ce addition contributed to the densification of corrosion products. The α-Fe phase preferentially underwent anodic dissolution reaction, generating corrosion product Fe2O3. The increase of soaking time resulted in the occurrence of anodic dissolution of Cu-matrix phase, along with the formation of Cu2O and Cu2Cl(OH)3.

Role of the γ′′ precipitation at the cell boundaries in enhancing the creep resistance of additively manufactured Inconel 718 alloy using the laser powder bed fusion technique

Laser powder bed fusion (LPBF) manufactured Inconel 718 superalloy (IN718) parts exhibit inferior creep properties compared to their conventionally manufactured (CM) counterparts due to the unique microstructural features associated with them. In this study, two different heat treatment schedules were employed, to critically examine role of distinct microstructural features associated with LPBF on the creep performance of LPBF IN718. Experimental results reveal that the creep performance is controlled by the Laves and γ′′ phases, as well as the cellular structure. Specially, the effective dissolution of Laves phases that are distributed along the grain and cellular boundaries in the as-fabricated state during solution treatment reduces the cavity nucleation sites and hence, extends the creep lifetime. The release of Nb into the matrix contributes to the precipitation of primary strengthening γ′′ phase during subsequent aging, enhancing the creep resistance. More importantly, the formation of a unique cellular structure with densely distributed γ′′ phase along the cellular boundaries, which exhibits high impediment of dislocation movement and inhibition of crack propagation, results in superior creep performance. The findings of the current study provide an effective heat treatment strategy for achieving high creep performance in LPBF nickel-based superalloys.

Microstructure Evolution and Mechanical Properties of In Situ TiB2/Al–Zn–Mg–Cu Composites by Electropulsing‐Assisted Solution Treatment

The traditional solution treatment is not completely applicable for in situ TiB2/Al–Zn–Mg–Cu composite due to the influence of TiB2 particles. This study investigates the impact of the electropulsing‐assisted solution (EAS) process on the microstructure evolution and mechanical properties of TiB2/Al–Zn–Mg–Cu composites. The nonuniform microstructure evolution related to the difference in temperature and current density is supported by simulative and experimental results. EAS treatment significantly enhances the degree of supersaturation, allowing phases surrounding TiB2 particles to dissolve without extensive overburning, unlike traditional solution treatments. This improvement is attributed to the reduced thermodynamic barrier and accelerated atomic diffusion, facilitated by both localized and average Joule heating effects and enhanced thermal electron/phonon scattering. Meanwhile, grain size remains stable during the temperature rise induced by EAS treatment. Furthermore, the mechanical properties of composites increase, among which the increase in strength is mainly ascribed to solid–solution strengthening, and the increase in elongation is related to multiple factors referring to TiB2 particles fracture and interface crack between the undissolved phases and matrix. This study provides an approach to achieve an efficient dissolution of phases aggregated with particles and without widespread overburning in particle‐reinforced Al matrix composites via electropulsing techniques.

Surface Reconstruction Enhanced Li-Rich Cathode Materials for Durable Lithium-Ion Batteries.

Regulating the distribution of surface elements in lithium-rich cathode materials can effectively change the electrochemical performance of cathode materials. Considering that the enrichment of Mn element on the surface is the main reason for the irreversible phase transition and dissolution of its surface structure, which in turn is the main reason for performance degradation. Based on the molten salt-assisted sintering method, a lithium rich cathode material with surface rich Ni and Co is designed and prepared. The surface enrichment of Ni and Co effectively reduces the dissolution of Mn, promotes the occurrence of irreversible collapse of surface structure from layered phase to rock salt phase on the material surface, improves the stability of surface crystal phase structure, and improves the cycling stability of positive electrode materials. Notably, after 500 cycles at 1 C current density, the discharge-specific capacity attained 189.8 mAh g -1, with a capacity retention rate of 88.9%, indicating a 42.1% improvement in capacity retention. Molten salt treatment is widely used in the modification of positive electrode materials. The research work will provide new ideas for improving the stability of lithium rich materials and promoting their commercial applications.

Sustainable enhancement of fly ash-based geopolymers: Impact of Alkali thermal activation and particle size on green production

Addressing the challenges posed by the slow reactivity of fly ash (FA) with alkali at ambient temperatures, this study delves into the enhancement of FA-based geopolymers through alkali thermal activation (ATA). The ATA process, conducted at 550°C for 1 h, significantly increases the availability of reactive silica and alumina, which are essential for geopolymerization. A critical focus of the research is the influence of FA particle size on ATA’s efficacy and the resultant mechanical properties of the geopolymers. Findings reveal that the ATA process facilitates the rapid dissolution of the vitreous phase in FA. This leads to a sequential release of silica and alumina, which is pivotal for the geopolymer’s matrix development. Notably, geopolymers synthesized from finely milled FA, post-ATA, demonstrate a marked increase in compressive strength, escalating from 30.51 MPa to an impressive 38.46 MPa. The study meticulously delineates geopolymerization into four distinct stages—initial dissolution, depolymerization, geopolycondensation and gelation, and final diffusion, with the initial dissolution and final diffusion stages being paramount in defining the reaction kinetics and the ultimate strength of the geopolymer. This enhanced understanding paves the way for optimizing FA utilization in geopolymers, promising a more sustainable and efficient pathway for producing construction materials with superior mechanical properties.

A novel process for producing Al-Si alloy utilizing aluminum-silicon oxide extracted from coal fly ash

As a kind of solid waste rich in aluminum and silicon resources, the comprehensive utilization of coal fly ash (CFA) will be of great significance to reduce environmental pollution and improve economic benefits. This work proposed a facile and environmentally friendly cleaning process for producing Al-Si alloy by molten salt electrolysis from CFA extract, aluminum-silicon oxide (ASO). The dissolution behavior and dissolution reaction mechanism of ASO were studied by high temperature visual dissolution experiment, thermodynamics analysis and phase analysis. Due to the chemical reaction between ASO and cryolite-based melt, ASO powder dissolves rapidly in melt and the dissolution rate of ASO is not determined by the phase compositions but by the mass ratio of Al2O3/SiO2. For replenishing the oxide concentration in the electrolyte as quick as possible, the proper mass ratio of Al2O3/SiO2 is in the range of 0.75–7.5. The electrochemical co-reduction behavior of Si (IV) and Al (III) ions on the W electrode was performed by cyclic voltammetry and square wave voltammetry. The results indicated that the reduction of Si (IV) ion in the melt was a two-step irreversible process. Hypoeutectic Al-Si alloy and eutectic Al-Si alloy were prepared by galvanostatic electrolysis using ASO as raw material. This innovative technology can realize high-value recycling of CFA resources and low carbon emission, low energy consumption production of Al-Si alloy.

Influence of forging pretreatments on microstructure evolution and surface roughness of Al 6061 alloy

Achieving ultra-smooth surfaces is the goal of aluminum optical manufacturing. Under certain processing conditions, improving the microstructure of aluminum and understanding its relationship with surface roughness requires systematic study. The grain structure and various types of second-phase particles are of paramount importance. This study analyzed the microstructure of 6061 alloy after undergoing severe plastic deformation under various processing conditions followed by T6 homogenization heat treatment. Utilizing a white light interferometer, a comparative analysis of the surface roughness was conducted on specimens that underwent single-point diamond turning to achieve a mirror finish. The assessment of surface roughness on machined surfaces is solely based on white light interferometry. The analysis and discussion focus on the effects of phases (causing scratches and voids), the grains and grain boundaries. Experimental findings signify: the grain size, grain boundary and residual second phase can both influence the surface quality, the increase in deformation temperature and accumulated strain both facilitate the dissolution and fragmentation of the secondary phases. However, they also contribute to some extent to grain growth, resulting in a minimum secondary phase area fraction of 0.87% and grain sizes reaching 147.8 μm. Subsequent heat treatments, while effective in reducing the negative impact of the phases, reveal noticeable step-like structures affecting the quality of surface roughness, with the lowest obtained Ra value being 0.8 nm. A proposed pretreatment method in cleaner ingot processing with lower alloy element content addresses the trade-off between reducing phases and controlling grain growth, aiming to achieve improved surface roughness, promoting the application of polycrystalline aluminum alloys in the field of optics manufacturing.

Synergistic optimization of microstructure and mechanical properties of AISI 430 ferritic stainless steel via dual-phase zone annealing process

This study systematically evaluated the impact of dual-phase zone annealing on the microstructure and mechanical properties of cold-rolled 430 Ferritic Stainless Steel (FSS), focusing on the phase transformation process from ferrite to austenite and the dissolution and precipitation behavior of the M23C6 phase. The annealing process significantly affects the microstructural characteristics of ferrite and martensite, including grain size, the distribution of grains of various sizes, aspect ratio, and phase content. The amount of martensite first increased and then decreased with rising annealing temperatures. The sample annealed at 1050 °C exhibited the highest martensite content of 29.5%. The variation in martensite content reflects the complex interplay between phase transformation kinetics and thermodynamic equilibrium. As the annealing time increased or temperature rose, the M23C6 phase at ferrite grain boundaries gradually dissolved and re-precipitated at higher temperatures. At lower temperatures, the M23C6 phase precipitated within martensite, but as the temperature increased, the precipitated phase diminished until it disappeared. Temperature changes affect the solubility of precipitates, atomic diffusion rates, and the uniform distribution of atoms across different phases. Appropriately increasing annealing temperature or extending annealing duration enhances the strength and hardness of 430 FSS. However, excessively high annealing temperatures lead to a decline in mechanical properties. The sample annealed at 1000 °C demonstrated the best mechanical properties, achieving a tensile strength of 783 MPa and an elongation of 16.0%. Furthermore, the analysis of fracture morphology and yield behavior in stress-strain curves further elucidated the macroscopic mechanical performance of the material.