Recrystallization Process Research Articles

Thermal deformation behavior and microstructure evolution of Fe−8.5Mn−1.5Al light−weight medium manganese steel

In this paper, Fe−8.5Mn−1.5Al light−weight medium Mn steel is used as the research object, and the hot compression test is conducted by Gleeble−3500 thermal simulation tester. The dynamic reversion and dynamic recrystallization (DRX) processes are analyzed according to the true stress−strain curve; the θ−σ work−hardening rate curve is plotted by P−J double differential method to analyze the influence law between work−hardening and dynamic reversion and recrystallization softening effect of the material; the DRX critical strain model is established to analyze the influence law of deformation parameters on DRX; Based on the dynamic material model theory, the hot working diagram and three−dimensional power dissipation diagram are constructed, and the best hot working area is determined by combining the microstructure of the material. Finally, based on the above research content, a systematic overview of the dynamic softening effects of DRX and dynamic recovery (DRV) will be provided.

Exceptional thermal stability of additively manufactured CoCrFeMnNi high-entropy alloy with cellular dislocation structures

CoCrFeMnNi high-entropy alloy (HEA) was additively manufactured (AM) by laser powder-bed fusion (L-PBF). The AM CoCrFeMnNi has prominent cellular dislocation structures with a small number of Mn-rich oxides. The thermal stability of the AM CoCrFeMnNi was investigated by isochronal annealing treatment at various temperatures from 400 to 1300 °C for 1 h. Microstructural analysis shows slow dislocation recovery, retarded recrystallization process, and precipitation of additional Cr-Mn based oxides during thermal annealing, resulting in exceptional thermal stability and retained high hardness at elevated temperatures. By thermodynamic calculations, a low stored energy of 1.31 MJ/m3 and a high activation energy of 353 kJ/mol for recrystallization were estimated for the AM CoCrFeMnNi. The exceptional thermal stability of the AM CoCrFeMnNi HEA is mechanistically attributed to the low crystallographic misorientations across the dislocation cell walls, sluggish atomic diffusion, and the pinning effects of the oxide nanoprecipitates.

Effect of recrystallization on bainite transformation and mechanical properties of complex phase steel with high formability (CH steel)

Herein, the effect of recrystallization on the bainite transformation and mechanical properties of CH steel were investigated using SEM, TEM, EBSD, dilatometry, and tensile testing machine. First, precipitation was introduced to hinder recrystallization by batch annealing. Subsequently, the competitive relationship between austenite transformation and recrystallization was revealed using different annealing processes. Finally, the effect of recrystallization on bainite transformation was analyzed, mainly including bainite morphology, fraction, transformation rate, bainite nucleation rate of untransformed austenite and austenite-bainite orientation relationship, as well as the effect on the mechanical properties. After batch annealing, a large amount of cementite and nanoscale (Nb, Ti)C precipitated in the hot-rolled sheet, the austenite transformation start temperature (Ac1) and the pearlite to austenite transformation end temperature (Ac1f)of the cold-rolled sheet increased, and the austenite transformation end temperature (Ac3) of the cold-rolled sheet decreased, and the austenite transformation process accelerated. The microstructure of annealed sheets is consisted of ferrite, granular bainite, martensite, and a small fraction of retained austenite. Carbide hindered the recrystallization process during the annealing process, resulting in significant refining of the grains. The lower degree of recrystallization promoted bainite transformation, providing more nucleation sites, higher grain boundary and autocatalytic nucleation activation energy, improving bainite's fraction and transformation rate. The bainitic ferrite was mainly lathy in the recrystallized zone and polygonal in the non-recrystallized zone. Both a K-S and an N-W relationship between retained austenite and bainite, while the N-W relationship in the non-recrystallized zone was relatively higher. Without severe loss of plasticity, hindering recrystallization increased the dislocation, grain refinement, and precipitation strengthening values of the samples, and the strength significantly improved. However, with the increase of annealing temperature, recrystallization fraction increased gradually, and the increase in strength became less noticeable.

Temperature Evolution, Material Flow, and Resulting Mechanical Properties as a Function of Tool Geometry during Friction Stir Welding of AA6082

The friction stir welding process was simulated for joining AA6082 aluminum alloy with the use of the computational fluid dynamics method. Two different tool geometries were used—a tapered cylindrical pin (simple pin) and a hexagonal pin with grooves (complex pin). The analysis of the simulations performed was discussed in terms of temperature evolution during the process, total heat input, residual stresses and material flow. Simulations revealed that a 5% higher temperature, equal to maximum 406 °C, was provided when using the complex pin than with the simple pin. Higher temperature and higher shear stresses during the welding with the complex pin caused the introduction of higher residual stresses in the weld. Experimental results on the produced welds allowed observation of the microstructure of the joints, hardness tests in cross sections and tensile strength tests. Due to the higher temperature during the process with the complex pin and the more efficient recrystallization process, grain refinement in the SZ was more pronounced. The average grain size in the stir zone for the weld produced with the complex pin was equal to 11 ± 1 µm, and in the case of the simple pin 14 ± 1 µm. The presented hardness profiles revealed that the weld produced with a complex pin had higher hardness in the stir zone, equal to 89.5 ± 1.3 HV, which is consistent with the Hall-Petch relationship. The obtained UTS values corresponded to the joint efficiency of 72.5 ± 4.9% and 55.8 ± 8.6% for the weld produced with the complex pin and the simple pin.

Highly Effective Salt-Activated Alcohol-Based Disinfectants with Enhanced Antimicrobial Activity.

Surfaces contaminated with pathogens raise concerns about the increased risk of disease transmission and infection. To clean biocontaminated surfaces, alcohol-based disinfectants have been predominantly used for disinfecting high-touch areas in diverse settings. However, due to its limited antimicrobial activities and concern over the emergence of alcohol-tolerant strains, much effort has been made to develop highly efficient disinfectant formulations. In this study, we hypothesize that the addition of a physical pathogen inactivation mechanism by salt recrystallization (besides the existing chemical inactivation mechanism by alcohol in such formulations) can improve inactivation efficiency by preventing the emergence of alcohol tolerance. To this end, we employed the drying-induced salt recrystallization process to implement the concept of highly efficient alcohol-based disinfectant formulations. To identify the individual and combined effects of isopropyl alcohol (IPA) and NaCl, time-dependent morphological/structural changes of various IPA solutions containing NaCl have been characterized by optical microscopy/X-ray diffraction analysis. Their antimicrobial activities have been tested on surfaces (glass slide, polystyrene Petri dish, and stainless steel) contaminated with Gram-positive/negative bacteria (methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica subsp. enterica Typhimurium) and viruses (A/PR8/34 H1N1 influenza virus and HCoV-OC43 human coronavirus). We found that additional salt crystallization during the drying of the alcohol solution facilitated stronger biocidal effects than IPA-only formulations, regardless of the types of solid surfaces and pathogens, including alcohol-tolerant strains adapted from wild-type Escherichia coli MG1655. Our findings can be useful in developing highly effective disinfectant formulations by minimizing the use of toxic antimicrobial substances to improve public health and safety.

The Beacon Heights “Tinguaite” (Phonolite): A recrystallised agpaitic ignimbrite in the Mesoproterozoic Pilanesberg alkaline complex, South Africa

AbstractAn extrusive rock unit in the Mesoproterozoic Pilanesberg alkaline complex that has been referred to as the “Beacon Heights Tinguaite” since the work of Shand (1928) has been reexamined in the field and studied by petrographic microscopy, scanning electron microscopy, and whole-rock major and trace element analysis. The new observations indicate that the unit (here informally renamed the “Beacon Heights Phonolite” to comply with current petrographical nomenclature) is a laminated, volcanic rock in which mafic layers rich in sodic pyroxene alternate on any scale with discontinous, felsic layers consisting of alkali feldspar, nepheline, sodalite and their alteration products natrolite and analcime. Highly strontian apatite, fluorite, a manganiferous pectolite-group mineral, sphalerite and pyrrhotite are minor to accessory minerals. In addition, the rock carries indicator minerals typical of agpaitic rocks (including lamprophyllite and eudialyte-group minerals and their replacement products). The rock contains abundant crystal fragments of felsic minerals (alkali feldspar, nepheline and sodalite), fragments and elongated lenses of nepheline syenite, some of which contain primary magmatic lamprophyllite, and rare armoured lapilli. The overall structure of the rock is that of a welded ashflow tuff (igmimbrite) affected by post-magmatic recrystallisation processes. Whole-rock major and trace element compositions suggest a compositional affinity with members of the agpaitic, intrusive Green Foyaite Suite of the Pilanesberg Complex, and probably also a genetic relationship. The Beacon Heights Phonolite is a rare, possibly unique, example of an ashflow deposit of agpaitic, highly silica-undersaturated composition.

Characterisation of Microstructure and Special Grain Boundaries in LPBF AlSi10Mg Alloy Subjected to the KoBo Extrusion Process

Grain boundary engineering (GBE) enhances the properties of metals by incorporating specific grain boundaries, such as twin boundaries (TB). However, applying conventional GBE to parts produced through additive manufacturing (AM) poses challenges, since it necessitates thermomechanical processing, which is not desirable for near-net-shape parts. This study explores an alternative GBE approach for post-processing bulk additively manufactured aluminium samples (KoBo extrusion), which allows thermo-mechanical treatment in a single operation. The present work was conducted to examine the microstructure evolution and grain boundary character in an additively manufactured AlSi10Mg alloy. Microstructural evolution and grain boundary character were investigated using Electron Back Scattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM). The results show that along with grain refinement, the fraction of Coincidence Site Lattice boundaries was also increased in KoBo post-processed samples. The low-Σ twin boundaries were found to be the most common Coincidence Site Lattice boundaries. On the basis of EBSD analysis, it has been proven that the formation of CSL boundaries is directly related to a dynamic recrystallisation process. The findings show prospects for the possibility of engineering the special grain boundary networks in AM Al–Si alloys, via the KoBo extrusion method. Our results provide the groundwork for devising GBE strategies to produce novel high-performance aluminium alloys.

Miniaturised experimental simulation of open-die forging

This study presents a novel experimental set-up for laboratory-scale simulation of cogging and open-die forging processes during ingot-to-billet conversion of advanced engineering alloys. The experimental set-up is designed to be cost-effective, employing a remotely operated manipulator assembly constructed from readily available “off-the-shelf” components used in conjunction with a conventional uni-axial load-frame - equipment that is available in most materials testing laboratories. Small test-bars of C101 copper alloy were subjected to multi-stroke cogging operations with intermittent rotation at ambient and elevated temperatures (20–600 °C). Prior to forging, the as-received material underwent heat treatments to coarsen the starting grain structure, and to help demonstrate the capability of the apparatus to achieve grain refinement via recrystallisation (dynamic and static) and recovery processes within the deformed material. The resulting microstructural evolution and mechanical property changes of the forged material have been investigated using light microscopy (LM), Vickers hardness (HV) testing, and electron backscatter diffraction (EBSD). The deformed C101 alloy exhibited measurable grain refinement after forging at elevated temperatures, thus demonstrating the effectiveness of the designed miniaturised open-die forging set-up.

Evaluation of tensile property and strengthening mechanism of Zirconia reinforced molybdenum alloy

In this experiment, the nano-ZrO2 particles reinforced molybdenum alloy with excellent mechanical properties were prepared through liquid-liquid doping process, and the comparison with TZM alloy prepared by solid-solid doping process was conducted. During the liquid-liquid doping process, the ZrO2 particles ensured the dispersion of the second phase in alloy because they reached molecular-level uniformity, and the hydrothermal synthesis preparation process enabled the ZrO2 particles in alloy to reach nanometer size level. In Mo-ZrO2 alloy, the small and dispersed ZrO2 can effectively block dislocation and passivation cracks; both the room temperature and high temperature performance of Mo-1.5 %ZrO2 alloy was better than that of TZM alloy. Based on the hindered recrystallization process, improved recrystallization temperature, as well as enhanced recrystallization strength thanks to the alloy pinning effect of ZrO2, the maximum tensile stress of Mo-1.5 %ZrO2 alloy at 1000 ℃ was about 14 % higher than pure molybdenum, and the maximum tensile stress of Mo-1.5 %ZrO2 alloy at 1400 ℃ was at least 45 % higher than pure molybdenum. Quantitative analysis shows that the strengthening effect of the second phase was the best during the recrystallization process.

Uncovering of the formation of rare earth texture and pseudo fiber bimodal microstructure in the high ductility Mg-2Gd-0.4Zr alloy during extrusion

The aim of this research was to elucidate the underlying mechanism involved in the formation of rare earth (RE) texture and pseudo fiber bimodal microstructure in the high ductility Mg-2Gd-0.4Zr alloy. The microstructure and texture evolution during the extrusion process were analyzed using various techniques, including optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and electron probe microanalysis (EPMA). The findings revealed that the RE texture in the extruded Mg-2Gd-0.4Zr alloy emerged during the dynamic recrystallization (DRX) process and was further strengthened during the subsequent static recrystallization and grain growth processes. The nucleation and growth of grains in the streamline region of Zr particles were delayed in comparison to other regions due to the pinning effect of Zr particles, ultimately resulting in the formation of pseudofiber bimodal microstructure in the extruded Mg-2Gd-0.4Zr alloy.

Influence of Re on the Plastic Hardening Mechanism of Alloyed Copper.

In this paper, we investigated the effect of adding rhenium to Cu-Ni-Si alloys on the mechanical properties and electrical conductivity of these alloys. The scientific objective was to analyze the effect of Re addition on the microstructure of heat- and cold-treated CuNi2Si1 alloys. Transmission electron microscopy (TEM, STEM) and scanning electron microscopy (EDS, WDS) were used to examine the microstructure. Orientation mapping was also performed using a scanning electron microscope (SEM) equipped with a backscattered electron diffraction (EBSD) system. In addition, hardness at low load and conductivity were tested. The obtained results showed that modifying the chemical composition of Re (0.6 wt%) inhibits the recrystallization process in the CuNi2Si1 alloy, which was cold deformed and then subjected to recrystallization annealing.

Reconstruction of MgAl-layered double hydroxides to LiAl-layered double hydroxides for scalable lithium extraction from salt lake brine

MgAl-layered double hydroxides (MgAl-LDHs) attract interest for lithium extraction due to their wide availability, high stability, and environmental friendliness. LiAl-layered double hydroxides (LiAl-LDHs) can be obtained by lithiation of MgAl-LDHs, yielding the facile preparation of adsorbents with high selectivity. Herein we synthesized porous MgAl-LDHs by a sol-gel method. MgAl-LDHs can be converted into LiAl-LDHs via dissolution and recrystallization process in LiOH solution. The structure of MgAl-LDHs dissolves, and Mg2+ exchange with Li+ in the solution to generate LiAl-LDHs. Mg2+ enter the solution. MgAl-LDHs and LiAl-LDHs were characterized using X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), N2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy (XPS). The granulation of MgAl-LDHs and LiAl-LDHs was facilitated by chemical/physical cross-linking of sodium alginate using CaCl2 solutions. The performance of lithium extraction was investigated using synthetic brines, and real salt lake brines. The results showed that MgAl-LDHs and LiAl-LDHs adsorbents registered an adsorption capacity of 9.7 and 6.4 mg/g, respectively, at pH = 6 in 300 mg/L of Li+ solutions. The kinetic analysis revealed that granulated MgAl-LDHs and LiAl-LDHs exhibited pseudo-second-order adsorption behavior attributed to the redox behavior. In the brine of East Taigener Salt Lake, the granulated MgAl-LDHs and LiAl-LDHs achieved an adsorption capacity of 15.5 and 9.1 mg/g, respectively. The granulated LiAl-LDHs and MgAl-LDHs are promising for scalable lithium extraction from salt-lake brines.

Bulk Defect Passivation for Full‐Inorganic Sb2S3 Solar Cells by Sulfur‐Atmosphere Recrystallization Process

Antimony sulfide (Sb2S3) solar cells have attracted extensive attention in silicon‐based tandem solar cells. The performance of Sb2S3 devices fabricated by the vacuum method is limited by sulfur vacancies (VS) and surface oxide defects during high‐temperature processes. Herein, amorphous Sb2S3 film based on low‐temperature rapid thermal evaporation (RTE) technique is fabricated to overcome S loss. Moreover, a sulfur‐atmosphere recrystallization strategy is further developed to obtain high‐quality absorbers from the amorphous film. The element content of Sb2S3 film is completely in accord with the stoichiometric ratio (2:3), and the surface oxides are effectively suppressed, enhancing VOC and fill factor. Compared to the control directly crystallized film, the defect concentrations of the S‐recrystallized Sb2S3 film are reduced by 61%, exhibiting better uniformity and higher PN junction quality. Ultimately, the full‐inorganic Sb2S3 solar cells (FTO/TiO2/Sb2S3/Au) achieve an efficiency of 6.25%. The S‐atmosphere recrystallization process can effectively passivate bulk defects (VS and Sb2O3) and suppress recombination to improve device performance, which will provide new prospects for vacuum method‐based Sb2S3 thin film solar cells.

Influence of recrystallization process on ionic conductivity of Ag6.75P0.25Ge0.75S5I based ceramic materials

This paper presents the results of research on ceramic materials based on Ag6.75(P0.25Ge0.75)S5I nanopowders with different grain size. Nanopowders with an average grain size of ∼100 and ∼160 nm, obtained by ball mill grinding, were characterized by XRD, SEM and diffuse reflectance methods. Ag6.75(P0.25Ge0.75)S5I ceramic samples were obtained by annealing pre-pressed disks at a pressure of 400 MPa. The microstructure and chemical composition of the obtained Ag6.75(P0.25Ge0.75)S5I ceramics were determined by SEM and EDS methods. The prepared Ag6.75(P0.25Ge0.75)S5I ceramics are chemically homogeneous with an average crystallite size of ∼1.99 and ∼2.29 μm and a low porosity of ∼6.4%. The electrical parameters of the investigated ceramics were characterized by the electrochemical impedance spectroscopy method. For both ceramics, there is an increase in total electrical conductivity with increasing frequency. It was established that the values of ionic conductivity of nanoceramic samples exceed the corresponding value of the bulk single crystalline sample. The influence of the recrystallization process and grain size on the electrical parameters of Ag6.75(P0.25Ge0.75)S5I ceramics is explained.

Investigation of thermal stability of aluminum matrix nanocomposites using functionalized MWCNTs

This work investigates the thermal stability of aluminum matrix nanocomposites reinforcing with functionalized multi-walled carbon nanotubes (MWCNTs). The effect of the chemical functionalization of MWCNTs (MWCNTs-COOH) was evaluated on the microstructure of these nanocomposites. One of the main challenges in producing metal matrix nanocomposites is obtaining a uniform dispersion of the reinforcement. The use of MWCNTs-COOH significantly impacted aluminum matrix nanocomposites' microstructure and mechanical properties. The nanocomposites produced with functionalized MWCNTs exhibit uniform dispersion, resulting in smaller grain sizes. However, concerning dislocation density and texture, the nanocomposites produced with non-functionalized MWCNTs exhibit a higher dislocation density and a different crystallographic orientation. For the heat-treated nanocomposites, it was observed that the reinforcement affects the recovery and recrystallization processes. This effect is more significant for nanocomposites produced with functionalized CNTs, resulting in a microstructure characterized by a significant fraction of deformed grains, smaller grain sizes, and higher mechanical properties.

Microstructure and mechanical property of bonding zones between Ta foil and steel plate fabricated by explosive welding

This work aims to produce a thorough comprehension concerning microstructure related properties of the joint interface between Ta foil and steel plate fabricated by explosive welding. For this, a self-developed explosive welding configuration was employed to join Ta foil and steel plate, and different microscopic methods were adopted to investigate its microstructures and mechanical properties. It was found that the Ta/Fe interface was featured by regular wavy structures with a well-defined amplitude and period. The melted zones were mainly observed within the vortex structures, and occasionally at the Ta/Fe interfaces, which were formed by intense mixing of participating metals. The EBSD analyses revealed a diversity of the grain structures near the Ta/Fe interface, such as formation of the curved and elongated grains in Ta matrix, and fine equiaxed and columnar grains in Fe matrix. Especially, several adiabatic shear bands (ASBs) characterized by small equiaxed grains were found in Fe matrix, which were due to stress wave concentration in the narrow paths, and the materials in these zones underwent a recrystallization process. Finally, the nanoindentation results revealed inhomogenous mechanical behaviors in the bonding zones, which could be well related to the changes of microstructure and chemical composition.

Effect of Different Stabilizers on Spherical Agglomerates of Montelukast Sodium by Quasi Emulsion Solvent Diffusion (QESD)

Abstract: The present study was focused on the spherical crystallization of an asthmatic drug, Montelukast Sodium (MLS) using quasi emulsion solvent diffusion (QESD) technique in which distilled water was an external phase and the internal phase consisted of Ethanol which acts as good solvent and Ethyl acetate as a bridging liquid for recrystallization and agglomeration process. Apart from being poorly water soluble, MLS exhibits poor flow and compressibility. The spherical agglomeration was carried out in the presence of different stabilizers like acacia, PEG 4000, sodium lauryl sulphate, span 40 and tween 80. The prepared agglomerates were characterized in terms of production yield, drug content, solubility, in-vitro release profile, Xray diffraction (XRD), and Fourier transform infra red spectroscopy (FT-IR).The optimized spherical agglomerates exhibited excellent physicochemical and micromeritic properties, solubility and dissolution rate when compared with pure drug .The XRD also revealed a characteristic decrease in crystallinity. The dissolution studies demonstrated a marked increase in the dissolution rate. FTIR study reveals there are no chemical changes in prepared recrystallized agglomerates. The considerable improvement in the dissolution rate of MLS from optimized crystal formulation was attributed to the wetting effect of polymers, decreased drug crystallinity, altered surface morphology and micronization. If this process can be scaled-up to manufacturing level, this technology has the potential to provide the directly compressed spherical agglomerates with improving the physicochemical and micromeritic properties

Hafnium isotope systematics of zircon in high-grade metamorphic rocks of the Anabar shield, Siberia: Radiogenic Hf without mantle input?

The timing for the onset of plate tectonics, along with the secular changes in the tectonic settings of continental crust formation, continue to be debated. Recent interpretations based on the increase in zircon 176Hf/177Hf ratios at the time of crystallisation (expressed as εHf(t) with respect to chondritic evolution) have been used to ascertain changes in geodynamic settings in the early Earth, specifically in the 3.8–3.6 Ga interval. This increase is widely interpreted as a change in magma generation, from source(s) dominated by ancient crust to source(s) dominated by juvenile inputs from the mantle. At issue, Hf isotope variations remain limited in the early Earth due to the long decay of the LuHf system. This feature, along with the scarcity of rocks and minerals of Eo/Mesoarchaean and Hadean ages, generate large uncertainties over the nature and the timing of the interactions between mantle and crustal reservoirs. The distinction between mantle and crustal sources becomes much clearer in the Palaeoproterozoic, and the study of ancient terranes with several billion years of protracted crustal evolution may hold the key to unlock complex mantle–crust interactions. Here we investigate high-grade metamorphic rocks from the Anabar shield, which contain zircons that crystallised between the Eoarchaean (oldest core at 3814 ± 16 Ma) and the Palaeoproterozoic (youngest core at 2251 ± 15 Ma and youngest rim at 1910 ± 21 Ma). The combination of in situ UPb and Hf isotope analyses in zircon indicates the formation of the continental crust in the Siberian Craton in the Eoarchaean, and a conspicuous metamorphic event at 2.0–1.9 Ga. We demonstrate that 2.0–1.9 Ga zircon ages reflect recrystallisation processes under subsolidus conditions, involving the breakdown of high-Lu/Hf minerals (i.e. garnet and pyroxene). The εHf(t) shift at 2.0–1.9 Ga towards more radiogenic values may not be related to a change in magmatic style and sources, but rather to resetting of the LuHf system in response to heating and metamorphic reactions on a mineral scale. Our findings challenge the widely-evoked mechanism of changes in tectonic style and magma sources to account for vertical arrays in the εHf(t) versus crystallisation age space. This calls for considering alternative options, including those based on petrographic data, when interpreting Hf isotope variations in the Hadean/Archaean detrital zircon record.

Investigations on the microstructural evolution and mechanical properties of Al-Cu-Al tri-metal strips fabricated through roll bonding and heat-treatment processes

ABSTRACT Aluminum alloys have recently become increasingly popular in the automobile industry. In this work, roll bonding technology was developed to fabricate the composite sandwich structure (tri-metal strip) of AA5083 alloy with a Cu interlayer. The apposite surface treatment, intermittent annealing, and thickness reduction resulted in desirable metallurgical characteristics and mechanical properties. The micrographs revealed crack-free flat joints, indicating excellent bonding between the layers of AA5083 and Cu. Also, the presence of sub-grains and dislocations between boundaries suggested a continuous and discontinuous recrystallization process. The phase composition analysis confirmed the formation of intermetallic compounds at the interface. The fabricated composite exhibited a microhardness of 124.2 HV and a tensile strength of 566.66 MPa.

Alkali-Induced Phase Transition to β-Spodumene along the LiAlSi2O6-LiAlSi4O10 Join

Due to the refractory nature of α-spodumene (LiAlSi2O6) and petalite (LiAlSi4O10), two major lithium minerals, conventional lithium recovery processes involve a high-temperature pre-treatment (>1000 °C) to induce a phase transition to tetragonal β-spodumene, an open structure allowing easier access to lithium through ion exchange. Considering that these high temperatures are not dictated by thermodynamics but rather sluggish kinetics, the study investigates the mechanisms enhancing the rate of transformation to β-spodumene at lower temperatures while minimizing the growth of metastable hexagonal β-quartz typically observed at the onset of the conversion. The heat treatment of natural α-spodumene revealed that rapid growth of β-spodumene veinlets is achieved at ≤600 °C by activation of alkali-rich fluid inclusions, through a dissolution–recrystallization process. For petalite, the mechanism of the phase transition, initiated at ≈750 °C is a solid-state transformation keeping crystallographic coincidence with the mineral host. Synthetic growth experiments along the LiAlSi2O6-LiAlSi4O10 join indicate a compositional dependence on the resulting β-phase structure, where minor sodium doping strongly favors β-spodumene, as the tetrahedral framework of β-quartz does not allow the extent of deformation to accommodate the larger alkali. These findings open opportunities for energy-efficient lithium recovery pathways where the phase transition and ion exchange can be achieved simultaneously without a high-temperature pre-treatment.