Precipitation Of Phase Research Articles

On the Importance of Precipitation‐Induced Surface Sensible Heat Flux for Diurnal Cycle of Precipitation in the Maritime Continent

AbstractThe Maritime Continent (MC) exhibits a pronounced diurnal cycle in precipitation, with many high‐resolution models overestimating the diurnal peak and predicting earlier precipitation over the islands than observed. We hypothesize that part of this model bias comes from ignoring precipitation‐induced surface sensible heat flux (QP). To test this conjecture, we performed simulations with and without QP for April 2009 and June 2006. The inclusion of QP reduced the bias in diurnal peak precipitation amplitude by 83% in April 2009 and 23% in June 2006. Similarly, the bias in precipitation peak timing decreased by 26% and 15%, respectively. This bias reduction was even more prominent during periods of heavier rainfall. This improvement in both the amplitude and phase of diurnal precipitation also led to a reduction in bias for total precipitation by ∼10%. These findings suggest that QP cannot be neglected over the MC, particularly during heavy precipitation.

Optimization of bobbin tool friction stir welding parameters of AZ31 magnesium alloy based on FEM and its influence mechanism on mechanical properties

Based on the 3D transient heat transfer theory, the finite element model of bobbin tool friction stir welding (BT-FSW) of AZ31 magnesium alloy sheet is established. The effects of different process parameters on the quality of BT-FSW joint of magnesium alloy were discussed using temperature distribution, mechanical properties, fracture morphology analysis, and EDS element distribution analysis. The results show that in the process of BT-FSW, the cross-section temperature of the plate is symmetrically distributed in an hourglass shape, the AS is slightly lower than that of RS, and the transverse temperature is distributed in an ‘M’ shape. When the rotating speed is 700 rpm and the welding speed is 180 mm/min, the weld surface is smooth, and its ultimate tensile strength can reach 81.82% of the base metal strength. The tensile specimen is quasi-cleavage fracture. When the heat input is insufficient, there are a lot of Al8Mn5 Precipitated phases in the TMAZ fracture zone, which increases the fracture brittleness of the joint. When the heat input is enough, the precipitated phase dissolves evenly, the river-like fracture surface of the joint retains the dimple characteristics, and the mechanical properties are improved.

Effect of Microporosity and Precipitation Phases on the Quality Index of AZ Series Magnesium Alloy Castings with Varying Grain Sizes

Effect of Microporosity and Precipitation Phases on the Quality Index of AZ Series Magnesium Alloy Castings with Varying Grain Sizes

Unveiling the mechanical anisotropy and related deformation mechanisms of heterostructured Mg alloy laminate with unique texture feature

In this study, a well-bonded AZ31/ZK60/AZ31 sandwich-structured laminate was prepared using extrusion. Microstructural heterogeneities in grain size, precipitate phases, and texture were evident between the constituent layers. Tensile testing revealed significant mechanical anisotropy in the laminates along the extrusion direction (ED), transverse direction (TD), and 45° directions, with the 45° direction samples exhibiting the highest tensile ductility, while ED and TD samples showed similar high strength. In-situ electron backscatter diffraction and slip trace analysis indicated that the heterogeneities in grain size and precipitates had minimal influence on the mechanical anisotropy of the laminates. Instead, texture emerged as the primary influencing factor, as it affected the initiation difficulty of basal slip and extension twinning mechanisms in various directions, thereby influencing the deformation coordination between the successive layers and resulting in varied mechanical responses in different directions.

Effect of σ Phase Precipitation on the Corrosion Resistance of Fe-Cr-Mn-Al Duplex Stainless Steel

Effect of σ Phase Precipitation on the Corrosion Resistance of Fe-Cr-Mn-Al Duplex Stainless Steel

Effect of deformation and cooling on non-equilibrium microstructure evolution and phase-transition mechanism of Ti–6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si

In the process of non-isothermal deformation of titanium alloy, the microstructure evolution is very complicated, which has direct effect on the properties of the titanium alloy. This study examines the effects of pure cooling and coupled deformation and cooling at the initial temperature of 940 °C and the cooling rate of 5,50 °C/s, and the strain rate of 0.1, 10s−1 respectively, on the microstructure evolution of Ti–6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si alloy (TC6) were investigated. The microstructure after cooling was characterised, and the mechanism of non-isothermal deformation on microstructure evolution and the mechanism of secondary α phase (αs) precipitation were revealed. The results show that the secondary α phase precipitates in large quantities after cooling to a certain temperature, and the secondary precipitated has an obvious inhibiting effect on the diffusion growth of the primary α phase (αp). Secondary α phases can be divided into lamellar and equiaxial types. When the temperature drops sharply, the fine secondary α phase can be precipitated directly from the β matrix. Due to the large number of dislocations generated by the deformation, many small secondary α phases can be generated during the rapid cooling process. The orientation relationship between α phase and β matrix is destroyed by the deformation, resulting in a weakening of the anisotropy, so that the secondary α phase remains equiaxial during the precipitation process.

Effects of sintering temperatures on the thermal conductivity and microstructural evolution of yttrium hydride monoliths by spark plasma sintering

In this study, YHx (where x represents the H/Y ratio) monoliths were fabricated using Spark Plasma Sintering (SPS), employing yttrium hydride powder as the raw material. The effects of different sintering temperatures (800 °C∼1200 °C) on the thermal conductivity and microstructural evolution of the YHx monoliths, including porosity, grain size, precipitated phases, and internal defects, were investigated. The results indicate that the sintering temperature exerts a significant influence on thermal conductivity and microstructural evolution. Notably, the thermal conductivity of these samples initially increases with rising sintering temperature, but subsequently decreases under identical testing conditions. This phenomenon is primarily attributed to the effects of porosity and precipitate phase. Furthermore, the presence of twin crystals also contributes to the reduction in thermal conductivity. The procedures provide an initial framework for understanding the relationship between thermal conductivity and the evolution of microstructure.

Impacts of the alloying elements and thermo-mechanical processing on the phase stability, crystalline structure, microstructure, and selected mechanical properties of Ti-(10-x)Al-xV (x = 0, 2, and 4 wt%) alloys targeted as external prostheses

This study aimed to characterize Ti-Al-V alloys submitted to thermo-mechanical processes and evaluate their impact on the crystalline structure, microstructure, coefficient of thermal expansion (CTE), selected mechanical properties, and cytotoxicity. X-ray diffraction (XRD) analysis revealed a major α phase, with V acting as a β-stabilizer. The cooling rate and the plastic deformation contributed to the formation of minor martensitic αʹ and β phases, with notable variations in cell parameters. The Energy-Dispersive XRD indicated the CTE was dependent on the alloying elements. Ti-10Al and Ti-8Al-2V depicted Widmanstätten laths and basket-weave structures, while Ti-6Al-4V showed typical features of β grain boundaries. Thermodynamic predictions aligned with the observed phase compositions. Vickers micro-hardness tests yielded values surpassing those of commercially pure titanium (CP-Ti), attributed to the synergistic effects of solid solution, phase precipitation, and strain hardening effects. And, elastic modulus approximated that of CP-Ti, largely due to the α phase's predominance. The solution treatment reduced the elastic modulus compared to the hot-rolled samples due to the stress relief and αʹ and β phase precipitation. Preliminary cytotoxicity assays confirmed the non-toxicity of the samples to cell viability. These findings suggest that the solutionized Ti-10Al sample is an economically viable candidate for fabricating external prostheses.

Expansion of thermodynamic calculation principle of multi-component alloy and its application in the study of thermodynamic properties of the Cr-Mo-Nb-V high entropy alloy

In this paper, based on the improved Miedema model and the quaternary alloy calculation model expanded by Chou model, the activity calculation model of the ternary alloy system is extended to the quaternary alloy system through the ternary alloy activity calculation model of Wagner and Ma Zhongting et al.. In addition, a new deviation function is used in the expanded quaternary alloy calculation model to calculate the thermodynamic properties of quaternary alloys, which meets the characteristics of both non-negativity and reducibility. Using the developed model, this paper calculates the thermodynamic data of each sub-binary, sub-ternary, and quaternary system in the Cr-Mo-Nb-V quaternary high entropy alloy system. Subsequently, this paper analyzes the interactions between components, predicts the possible precipitated phases in the alloy system, and explains the possibility of forming a solid solution in the alloy system. The final results are consistent with those shown in the literatures on studying the Cr-Mo-Nb-V quaternary alloy system, which verifies the applicability of the developed model in the miscible alloy system, enriches the thermodynamic database of Cr-Mo-Nb-V alloy, and provides theoretical reference and ideas for the design of multi-component alloys.

Effect of aging state on microstructure and properties of heat affected zone in Al-Mg-Si-Cu alloy welded joints

The softening of the heat affected zone (HAZ) remains a significant challenge in fusion welding of novel Al-Mg-Si-Cu alloy, and the underlying mechanisms vary across different aging states. However, limited research has been conducted on this topic. Therefore, this study investigates the influence of various aging states on the microstructure and mechanical properties within the HAZ of welded joints by selecting extrusions treated with T4, T5, and T6 heat treatments. The results indicate that the increase in hardness of HAZ I is attributed to solid solution strengthening. In the HAZ I, the precipitated phases are mostly dissolved into the matrix under the influence of a peak temperature of 464.6 °C, and no residual precipitated phase is detected in T4 and T5 alloy joints, while some undissolved Q phase is observed in T6 alloy joint. The decrease in hardness of HAZ Ⅱ is attributed to the limited precipitation of coarse β" and Q' phases for the T4 alloy welded joints, which weakens the solid solution strengthening. However, the softening mechanisms in the HAZ Ⅱ of the T5 and T6 alloy joints are ascribed to the dissolution of β" and subsequent precipitation of Q' and Q phases. HAZ Ⅲ, close to the base metal, exhibits a lesser degree of influence and thus experiences a gradual recovery in hardness. This study can provide theoretical guidance for the exploration of high-strength, heat-resistant aluminum alloys.

Influence of Solid Solution Time on Microstructure and Precipitation Strengthening of Novel Maraging Steels

Effective subsequent heat treatment is crucial for achieving the desired microstructure and excellent mechanical properties in laser-deposited high-performance maraging steel. In this paper, we systematically investigate the synergistic relationship and tuning mechanism of different solution treatment times on the microstructure-property synergy of new maraging steels fabricated using laser direct energy deposition (LDED). To determine the optimal heat treatment process, solution treatment was conducted at 840°C for varying durations, followed by aging at 530°C for 2 hours to induce precipitation strengthening. The results indicate that after 2 hours of solution treatment, the alloy exhibits optimal ductility with an elongation of 7.90% ± 0.15%, attributed to the refinement of the martensitic matrix and precipitated phases, along with the formation of a small amount of residual austenite. When the solution treatment time is extended to 4 hours, the alloy achieves its highest tensile strength, reaching 1958 ± 24 MPa. However, the elongation decreases to 7.31% ± 0.12% due to the coarsening of the martensite and secondary phase particles. After 6 hours of solution treatment, significant coarsening and aggregation of the martensite and Fe2Mo intermetallic compounds markedly reduce the hardness, strength, and toughness of the alloy. By adjusting the solution treatment time, the size, morphology, and distribution of the martensitic matrix, Fe2Mo, and nanoscale precipitated phases play a critical role in the strengthening and fracture processes. Therefore, optimizing the precipitation behavior of the martensitic matrix and Fe2Mo intermetallic compounds through rational solution heat treatment is key to enhancing the mechanical properties of laser-deposited new maraging steels.

The Microstructure and Corrosion Characteristic of Al-10 wt.%RE (Re= Ce, Nd, La, Y) binary Aluminum Alloys in Natural Seawater

This study presented a thorough investigation into the microstructure, precipitated phases, and corrosion resistance of Al-10wt%Ce, Al-10wt%Nd, Al-10wt%La, and Al-10wt%Y binary alloys when exposed to natural seawater. The microstructural analysis, conducted using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM), revealed the presence of distinct precipitated phases. The distinct precipitated phases Al3Ce, Al3Nd, Al11La3, and Al3Y, respectively, have different morphologies and are expected to influence the corrosion resistance. The corrosion behavior of these alloys was evaluated through natural seawater immersion tests and electrochemical experiments, which demonstrated varying degrees of corrosion resistance. The average corrosion mass loss rates and average corrosion depths of the alloys in natural seawater were found to follow the order: Al-Y<Al-Ce < Al-La < Al-Nd. Theoretical explanations for the experimental outcomes were provided by analyzing the different types of precipitates, the electronic structures, and the crystallographic structures of the rare earth elements involved. This research contributes valuable theoretical and empirical data, supporting the application of rare earth aluminum alloys in structural materials for marine equipment.

Effect of heat treatment process on microstructure and properties of copper modified 1Cr11MoNiW1VNbN

Abstract The purpose of this study was to investigate the effects of Cu element content and heat treatment process on the microstructure and mechanical properties of 1Cr11MoNiW1VNbN martensitic heat-resistant steel. Microstructure was characterized by optical microscope (OM) and scanning electron microscope (SEM), tensile testing machine and impact testing machine were used to test the mechanical property. The results show that with the increase of Cu content, the precipitation of Cu-rich phase in the steel increases, while the formation of δ-ferrite and coarse carbides decreases, which significantly improves the strength of the material. When the Cu content is 2.14%, the tensile strength at 600 °C reached 542 MPa and the yield strength reached 484 MPa after normalizing at 1000 °C and tempering at 700 °C. With the increase of the normalizing temperature, the strength of the test steel decreases slightly, and the impact energy improved significantly.

Microstructural evolution and mechanical properties of Al2O3/Al joint bonded by Bi2O3-B2O3-SiO2-ZnO-Al2O3 glass

A glass filler of 60Bi2O3-20B2O3-10SiO2-5ZnO-5Al2O3(mol%) was utilized to join 99Al2O3 ceramic and Al alloy 1060 at low temperature, which effectively addressed the negative impact caused by the indelible oxide film on the aluminum surface during the conventional process. Prior to the joining process, the surface morphology and thermophysical properties of the glass filler were investigated. Additionally, the wetting behavior of the glass on both the Al2O3 substrate and Al substrate was confirmed. Subsequently, the interfacial microstructure of the Al2O3/Al joints was analyzed in detail and the mechanical properties of the joints were evaluated under different temperatures and holding times. The shear strength of the joints reached a maximum value of 30.25 ± 1.0 MPa at 460 °C for 30 min. The precipitation and growth of the Bi24B2O39 phase improved the mechanical properties of the joints with increasing temperature and holding time. However, high temperatures and long holding times resulted in the precipitation of a large number of crystals in the joints, leading to embrittlement, which severely reduced the mechanical properties of the joints.

Investigation on effect of L12 and B2 phases on tensile properties and mechanisms of Al0.3CoCrFeNi high entropy alloy through aging treatment

Al0.3CoCrFeNi high entropy alloys (HEAs) have excellent mechanical properties due to the large tunability of microstructures, which makes them one of the most promising candidates for engineering application. In the aspect of enhancing tensile properties, precipitation strengthening was verified effective in this HEA and more studies are needed to deepen relative understanding. In this work, Al0.3CoCrFeNi HEAs with coarse-grained single FCC (A) and fine-grained triplex FCC + B2 + σ (B) structures were aged at different temperatures and times to precipitate second phases, and the tensile properties and mechanisms of aged specimens were studied. The results showed that aging of A resulted in the main precipitation of L12 phases throughout FCC matrix and increasing aging temperature obviously increased L12 size, whereas increasing annealing time had minor effect on phase coarsening. At small L12 size of ~2.0nm, stacking fault shearing mechanism was activated during tension and planar dislocation configurations were formed, leading to simultaneous increase of strength and ductility. With increasing L12 size to ~10.0nm, the deformation mechanism was transformed into anti-phase boundary shearing and Orowan bypassing and wavy dislocation configurations predominated, which resulted in the significant increase of yield strength from ~263MPa to ~433MPa without sacrificing notable ductility. On the other hand, aging of B induced the formation of fine B2 phases at residual dislocations and enhancement of tensile yield strength from ~705MPa to ~759MPa. The ductility decreased slightly from ~32% to ~28%, which was related to the plastic deformation of B2 phases. However, it was found that the tensile strengths could not be continuously increased by further increasing aging temperature or time. These findings provide insights into the development of precipitation strengthened HEAs with good mechanical properties.

Influence of different rolling passes and deformation amounts on the microstructure evolution and strengthening mechanism of Cu-Ni-Si alloy

Under the condition of controlling the total rolling deformation to 80.0%, the effects of multi-pass rolling, the ratio of deformation between the first and second stages in two-stage rolling, and aging parameters on the microstructural evolution and property enhancement of Cu-Ni-Si alloy were investigated. The results showed that the second-stage rolling promotes the formation of high-density dislocations, significantly enhancing dislocation strengthening. Simultaneously, the high-density dislocations facilitate the precipitation of the second phase during aging, and concurrently improving the strength and electrical conductivity of the alloy. In the two-stage rolling and aging process, a ratio of first-stage to second-stage rolling deformation less than 1 yields superior comprehensive properties. Specifically, when the first-stage rolling deformation is 35.0% and the second-stage deformation is 68.8%, the alloy achieves an optimal electrical conductivity of 49.53% IACS, hardness of 272.9 HV0.1, tensile strength of 773.0 MPa, and yield strength of 723.3 MPa. This is because a rolling ratio less than 1 results in higher dislocation density; the δ-Ni2Si precipitates have a coherent relationship with the Cu matrix, the interparticle spacing of precipitates is smaller. The average grain size is refined from 1.29 μm to 1.08 μm, significantly enhancing grain boundary strengthening. Dislocation strengthening and second-phase strengthening are the primary strengthening mechanisms of the alloy, and the calculated alloy strength agrees well with the experimental values, with errors less than 3.4%. Additionally, the Avrami equation in phase transformation kinetics was utilized to study the variation law of the volume fraction of the δ-Ni2Si phase with aging time.

Eco-friendly recovery and preparation of high purity nano silver powders from retired photovoltaic solar cells

With the increasing deployment of photovoltaic modules, recycling of waste photovoltaic has become a topic of great concern. Silver (Ag) represents a significant resource in retired crystalline silicon solar cells (RCSSC). However, conventional methods for the recovery of silver are based on the use of harmful inorganic acids, which give rise to environmental concerns. Furthermore, the use of unsuitable chlorine sources may result in the production of target products with a low level of purity. Herein, we reported a new method featured with eco-friendly mixed organic acid to extract and recycle Ag from retired crystalline silicon wafers. Single-factor experiments and response surface optimization experiments were carried out to find the optimal conditions in the leaching step. A process comprising chlorination precipitation, ammonia dissolution, and liquid phase reduction was constructed for the production of silver powder from the leaching solution. This approach resulted in a high silver leaching yield of 97.38 % and silver purity of 99.85 % before purification with an average particle size of 229.7 nm.

Effect of Ag–Te alloys on pH sensitivity of Ag2O–TeO2 glass/stainless steel enamel

Glass pH sensors are unsuitable for in vivo biomedical, clinical, or food applications because of brittleness of glass, the difficulty in measurement of small volumes and complex matrices, and the need for calibration. Herein, a novel enamel reference electrode for pH sensors is developed using a binary xAg2O·(100–x)TeO2 glass/stainless steel (SUS) electrode. Subsequently, the effects of Ag2O content on the precipitated crystalline phases and pH sensitivity of Ag2O–TeO2 glass/SUS electrodes are examined. The results indicate that the xAg2O·(100–x)TeO2 glass/SUS samples exhibit relatively low pH sensitivity. The pH sensitivities of the samples can be classified into two distinct groups. The first group, comprising samples with an Ag2O content of 25 mol% or more, exhibits a pH sensitivity higher than 10 %. The second group, comprising samples with an Ag2O content of 22 mol% or less, exhibits a pH sensitivity of less than 10 %. The pH sensitivity tends to decrease with increase in stutzite fraction in Ag–Te alloys. Results of X-ray diffraction measurements and transmission electron microscopy observations indicate that the hessite and stutzite Ag–Te alloys, which are minor and conductive, are the primary contributors to the low pH sensitivity observed. Moreover, the pH sensitivity of xAg2O·(100–x)TeO2/SUS is observed to be between those of the Ag–Te alloy and the Ag2O–TeO2 glass matrix. We propose occurrence of an electrical shunt should occur between the Ag–Te alloy and the Ag+-ion conductive Ag2O–TeO2 glass matrix. Regarding xAg2O·(100–x)TeO2 glass/SUS, the 20Ag2O·80TeO2 glass/SUS to 21Ag2O·79TeO2 glass/SUS compositions represent promising candidates as for KCl-leakage-free reference electrodes for pH sensors.

Investigation of the microstructure, electrical and mechanical properties of Al-CNTs-B4C composite prepared by double-step stir casting for power transmission conductor

Abstract Monolithic aluminium alloy is a modern engineering material that is in high demand owing to its excellent performance and versatility. It has a high electrical conductivity, low density, high strength- to- weight ratio, and high resistance to corrosion. However, it lacks adequate resistance to creep, fatigue, stable microstructure, and strength at elevated temperatures. To overcome these deficiencies, aluminium matrix composites are developed. This work focuses on an experimental investigation of the microstructure, mechanical strength, and electrical conductivity of Al-CNTs-B4C composite consolidated by a double-step stir casting technique. An x-ray diffractometer, transmission electron microscopy, and a field-emission scanning electron microscope fitted with energy dispersive x-ray spectroscopy were used to characterize the start-up powders and the cast samples. A Brinell tester was used to measure the microhardness of the cast samples. A four-point probe meter was used to determine the electrical conductivity. The microstructural results revealed formation of Al4C3 and Al3BC intermetallics, B4C phase and amorphous carbon precipitate. Marginally improved electrical conductivity of 33.33 × 107 S m−1 (65.1% IACS) was obtained with Al-5CNTs-15B4C, together with high microhardness of 725.72 MPa. The microhardness improved by 94.7% over monolithic pure Al. The double-step stir casting enhanced the homogenous dispersion of the reinforcements. The improvements in the mechanical properties and electrical conductivity were attributed to the synergy between B4C and CNTs which induced Orowan looping, load transfer effect, plastic deformation and dislocation pinning in the composite. It is recommended that this composite will perform creditably in power transmission.

Roles of Al/Ni ratio and solidification cooling rate in grain boundary engineering of AlxCrFeMnNi(2-x) high entropy alloy

In this work, the roles of Al/Ni ratio and solidification cooling rate in grain size, dendrite morphology and grain boundary characteristic of the AlxCrFeMnNi(2-x) (x = 0.3, 0.7 and1.0) high-entropy alloys (HEAs) were investigated. The results show that the increasing of Al/Ni ratio results in a transition from single-phase FCC to dual-phase BCC + B2 along with the reverse precipitation behavior of BCC phase. While the phase composition is not affected by solidification cooling rate. With the increasing of Al/Ni ratio and solidification cooling rate, a significant columnar-to-equiaxed transition (CET) behavior can be observed. That is, grain refinement and transition from columnar dendrites to equiaxial and cellular dendrites. This is mainly attributed to the constitutional supercooling (CS) caused by the solute interaction effect of Al and Ni, and which can be evaluated by P and Q parameters. In addition, in-situ formation of serrated grain boundaries (SGBs) can be also observed in solidification microstructures, and with the increasing of Al/Ni ratio, the proportion of SGBs increases gradually. Whether the B2 precipitated phase is present or not, the formation mechanism of SGBs is mainly attributed to the lattice strain energy caused by the segregation of Al and Ni. The strategy simultaneously achieving grain refinement, CET and in-situ forming SGBs during solidification by tailoring Al/Ni ratio opens new perspectives for grain boundary engineering.