Precipitates In Matrix Research Articles

Evolution of new topologically close-packed phases P and R upon long-term isothermal aging of laser powder bed fusion processed Hastelloy X

The evolution of secondary phases and the microstructure-property relationship of laser powder bed fusion processed Hastelloy X during long-term isothermal aging have been studied. Hastelloy X was subjected to prolonged thermal exposure at two different temperatures, 800 °C and 950 °C, for 500 h in each case to explore the distribution and evolution of secondary phases. A thorough microstructural investigation employing transmission electron microscopy exhibited the evolution of M23C6 carbides along with the topologically close-packed (TCP) phases such as µ, R and P. At 800 °C, the intergranular formation of M23C6 was characterized by a perfect cube-on-cube orientation relationship with the matrix phase. Moreover, at the same temperature, the µ phase is uniformly distributed in the matrix as well as in the intergranular regime. The main finding includes the evolution of P and R phases at 950 °C. At this temperature, the presence of new TCP phases, i.e., R and P (which had not been previously observed in Hastelloy X), evolved at the intergranular regime, whereas no carbides or the µ phase were evident. Also, at this temperature, the matrix region was found to be devoid of any kind of precipitation. All the TCP phases were characterized by planar defects attributed to accommodate the lattice misfit strain. The room temperature and elevated temperature (800 °C) tensile tests demonstrated higher yield strength and lower elongation of the 800 °C specimen compared to the 950 °C specimen, which was attributed to the excessive matrix and intergranular precipitation.

Evolution of microstructure and tensile behavior in an interstitial strengthened high entropy alloy

The microstructural evolution and mechanical properties of Fe61.5Cr17.5Ni11.5Al8C1.5 high-entropy alloys (HEAs) were investigated to establish an optimal set of annealing conditions that would result in reasonable recrystallized fractions across the different temperatures and durations. The evolution of the microstructure was analyzed, tracking the transformation from the rolling texture to the recrystallization texture, as well as any phase transformations that occurred. The grain size distribution, overall microstructural features, and the effects of annealing temperature and time on the tensile properties of the HEAs were examined and discussed. The alloy was subjected to cold rolling and subsequent annealing treatments, revealing a single FCC phase after homogenization at 1260 °C. The cold-rolled samples retained the FCC structure at lower annealing temperatures (400 °C and 500 °C) but underwent a phase transformation to BCC at higher temperatures (600 °C to 900 °C). Microstructural characterization demonstrated that cold rolling introduced a high density of dislocations, while annealing facilitated recrystallization and grain growth. The tensile tests indicated that HEA samples exhibited a yield strength of 570 MPa and ductility of ∼36 % with large grain size after a long annealing at elevated temperature. In contrast, after being heat-treated at 1200 °C for 2 min, HEAs restrict FCC-to-BCC phase transformation and exhibit small grain size (3.2 µm) with M23C6-like carbide precipitation in the FCC matrix. Smaller grains provide additional boundaries, which restrict dislocations to bypass these boundaries. While carbide precipitates at grain boundaries and inside grains, it strengthens the material by pinning grain boundaries and restricting dislocation movement, resulting in a yield strength of 610 MPa and ductility of ∼41 %.

Effect of Cr Additions on the Coarsening Resistance of β′ Precipitates in Ferritic Fe–Ni–Al Alloys

The effect of Cr additions ON the coarsening of β′(NiAl) precipitates in (Fe,Cr)‐α matrix is studied using Fe–10%Ni–15%Al–15%Cr (FAN15Cr) and Fe–10%Ni–15%Al–22%Cr (FAN22Cr) alloys. Specimens are homogenized and subsequently aged at 850, 900, and 950 °C for different periods of time. The characterization is carried out with conventional and high‐resolution scanning electron microscopy, transmission electron microscopy, and Vickers hardness tests. Results indicate that the addition of Cr leads to an increase in the activation energy and the coarsening kinetics at high temperatures. The precipitate morphology during aging evolves from spheres with a random distribution, followed by cuboids aligned in preferential orientations and the formation of clusters. As aging progresses further, the morphology changes to semirounded precipitates with a polyhedral surface as revealed by the etching process. Transmission electron microscopy results reveal the formation of a dislocation network indicating a state of semicoherency in the precipitate–matrix interface. The activation energy for the coarsening process is determined from the coarsening kinetic constants. While the activation energy for the coarsening in FANCr15 is close to similar alloys, the value for FAN22Cr is unusually high and probably related to the dislocation networks observed.

Evolutions on Microstructure and Impact Toughness of G115 Steel after Long-Term Aging at 700 °C

The microstructure and impact toughness evolution of G115 steel after long-term (ranging from 500 h to 10,000 h) aging at 700 °C were investigated in this study. The results showed that the microstructure of the G115 steel evolved from a finer-grained matrix with minor precipitates to a coarse-grained matrix with more precipitate with aging time, presenting a decrease in the local deformation degree in the matrix. The impact toughness of the steel decreased with aging time, presenting the largest decline at the initial aging times. The decrease in impact toughness was attributed to the coarsening of precipitates (M23C6 and Laves phase) in the steel matrix. The stable impact toughness during the whole aging process (from 500 h to 10,000 h) should be related to the comprehensive effects, including the precipitation of the Laves phase, the increase in high-angle grain boundaries, and the softening of the metal matrix.

Microstructural evolution and mechanical behavior of activated tungsten inert gas welded joint between P91 steel and Incoloy 800HT

This study examines the welded joint between P91 steel and Incoloy 800HT using the activated tungsten inert gas (A-TIG) welding process. The focus is on analyzing the microstructure and evaluating the mechanical properties of joints made with different compositions of activating flux. Owing to the reversal of the Marangoni effect in which the conventional direction of molten metal flow in the weld pool is reversed due to the application of oxide-based fluxes, a complete depth of penetration of 8 mm was successfully achieved. Conducting mechanical tests, such as microhardness, tensile, and Charpy impact toughness tests, elucidates the behavior of the welded specimens under different loading conditions. The findings highlight the effects of grain size, dislocations, and the evolution of fine-sized precipitates in the high-temperature matrix. This study highlights the importance of choosing suitable flux compositions to achieve consistent penetration and dilution in the base metals. Insights into different failure modes and the influence of temperature on the tensile strength were evaluated. Beneficial mechanical properties of the joints (meeting the criteria of ISO and ASTM standards) were found: ultimate tensile strength of 585 ± 5 MPa, elongation 38 ± 2%, impact toughness of 96 ± 5 J, and maximum microhardness of 345 ± 5 HV.

Evolution of microstructure and spectral characteristics of silver nanoparticles in photo-thermo-refractive glass

Photo-thermo-refractive (PTR) glass is widely used in volume holographic devices. After photo-thermo treatment, silver nanoparticles (Ag-NPs) and sodium fluoride (NaF) crystals can precipitate in the glass matrix to realize refractive index modulation (RIM). The Ag-NPs are the foundation for subsequent precipitation of NaF crystals and significantly affect the absorption and luminescence characteristics of PTR glass. Within the nucleation temperature range of 440 °C-480 °C, the Ag-NPs formed by photo-thermo-induced nucleation are within 5 nm. Increasing nucleation heat treatment time causes an increase in the average size of Ag-NPs and the thickness of AgBr shell. Increasing the UV exposure dose significantly increases the concentration of Ag-NPs. The long nucleation time and high UV exposure doses can both increase the content of luminescent silver molecular cluster [Agm]n+, while high nucleation temperatures over 500 °C cause fluorescence quenching of PTR glass due to the formation of large Ag-NPs over 10 nm and NaF crystals. The formation of Ag-NPs effectively reduces the crystallization temperature of PTR glass. The refractive index of PTR glass can be effectively controlled by adjusting the parameters of photo-thermo-induced nucleation. Under the condition of crystallization at 550 °C for 30 min, a maximum RIM value of 1500 ppm can be achieved.

Microstructures and compositions of nano-precipitates and reverted austenite in custom 455 stainless steel in over-aged condition studied by transmission electron microscopy and atom probe tomography

The microstructures and nano-scale precipitate phases of Custom 455 stainless steel quenched from 850 °C and over-aged at 480 °C for 256 h have been studied in a quantitative way by using transmission electron microscopy and atom probe tomography. The results show that plate reverted austenite is formed between the martensite laths. In the reverted austenite, a rod-shaped Ni3Ti phase particle of about 40 nm long is precipitated at the interphase interface between martensite and reverted austenite, with an adjacent Cu-rich precipitate with a size of ∼20 nm. In the martensite, spherical G-phase particles with a diameter of about 8.0 ± 1.6 nm are precipitated adjacent to the Cu-rich precipitates with a size of about 10.0 ± 2.0 nm. These Cu-rich precipitates in the martensite are much smaller than those in the reverted austenite, but have a ten times higher number density than that in the latter. The orientation relationships between the martensitic matrix, reverted austenite, Ni3Ti phase, G-phase and Cu-rich precipitates are: (01−1)M//(1−11)γ//(0004)η//(02−2)G//(111)Cu,[111] M //[011]γ//[2−1−10]η//[111]G//[11−2]Cu.

Inhomogeneity and anisotropy of Al-Zn-Mg-Cu alloy manufactured by wire arc additive manufacturing: microstructure, mechanical properties, stress corrosion cracking susceptibility

ABSTRACT In this study, Al-Zn-Mg-Cu alloy components were prepared using wire arc additive manufacturing (WAAM). Through multi-scale characterisation technology, performance testing and slow strain rate tensile (SSRT) testing, the microstructure, mechanical properties and stress corrosion cracking (SCC) susceptibility of WAAM Al-Zn-Mg-Cu components were studied, revealing the generation mechanism of inhomogeneity and anisotropy. The results show that with the increase of WAAM thermal cycles, the matrix precipitates (MPs), grain boundary precipitates (GBPs) and precipitation-free zones (PFZ) evolve in different paths and increase to varying degrees, resulting in performance decrease and increase in stress corrosion susceptibility, so the inhomogeneity is mainly attributed to differences in precipitated phases. The Inter-layer inclined to the scanning direction and the Inner-layer inclined to the building direction led to anisotropy in tensile strength and SCC behaviour, so the anisotropy is mainly attributed to the grain orientation and fracture mode.

Numerical and experimental investigation of the dynamic mechanical behavior of precipitation-strengthed NiCoCrSi0.3C0.048 medium-entropy alloy

An extended crystal plasticity model and an optimized neural network are established to investigate the mechanical behavior of CoCrNiSi0.3C0.048 Medium entropy alloy (MEA) with a three-level hierarchical precipitation structure under dynamic compressive deformation at a variety of ranges of strain rates. The interaction between the matrix and first-level precipitates is described by a presented hybrid representative volume element RVE model, involving the effects of volume fraction (Vf), radius and geometric distribution on heterogeneous deformation. Effects of second- and third-level precipitates are realized through the extended crystal plasticity constitutive model, reflecting the motion mechanism of dislocations near the precipitates in the form of initial slip resistance. Meanwhile, this study investigates the influence of the presence of primary precipitates on the initiation of slip systems within special grains with Goss or S orientations in the matrix. Additionally, it provides a more in-depth explanation of the underlying principles behind the suppression of Goss texture formation by the precipitates from the perspective of slip systems analysis. The changing of volume fractions affects flow stress evolution. Avoiding suffering from expensive computational consumption by the crystal plasticity finite element method, an artificial neural network model optimized through a genetic algorithm, is presented to predict stress-strain responses and texture evolution results under varying compression strain rates. A reliable dataset derived from crystal plasticity finite element models and experimental results is utilized to train, test, and validate the genetic algorithm-based artificial neural network model. This model demonstrates good prediction capability in dynamic mechanical behavior and texture evolution, showcasing the feasibility and efficacy of the proposed neural network model. Compared to the CPFEM method, neural network models can greatly improve computational efficiency.

Research Progress on Fluoride Solution Promoting the Survival of Replanted Teeth

Tooth replantation is an operation in which the lost teeth due to various reasons are treated and replanted in the alveolar socket. The key lies in the regeneration of the alveolar blood vessels and the regeneration of the alveolar bone. Fluoride has been proved to be a substance that promotes the growth of bone cells and has been widely used worldwide. Fluorine is a rare element that mixes with bone minerals during the osteogenic phase. It is a known non hormonal factor that can affect bone formation and has a bidirectional regulatory effect on bone formation. Long term low doses can promote bone formation, while high doses can cause osteoporosis or osteosclerosis. Osteocalcin can regulate bone metabolism, maintain normal bone calcification, inhibit cartilage calcification and irregular crystal precipitation. The mechanism of action of fluoride is that fluoride can stimulate osteoblasts to secrete osteocalcin, allowing more hydroxyapatite crystals to combine with it and precipitate in the bone matrix. Therefore, an appropriate concentration of fluoride solution can promote bone remodeling of alveolar bone and dentin. Through the effect of fluorine on bone cells, fluoride can be applied to tooth replantation surgery in order to improve the success rate of surgery. It was found that fluoride can regulate bone formation by stimulating the proliferation and differentiation of immature osteoblasts, ultimately affecting tooth replantation.

The Effect of Carbide Concentration at Grain Boundaries on Thermal Stresses in Castings for Heat Treatment Furnace Tooling

Austenitic Fe-Ni-Cr alloys are commonly used for the production of castings intended for high-temperature applications. One area where Fe-Ni-Cr castings are widely used is the equipment for heat treatment furnaces. Despite the good heat resistance properties of the materials used for the castings, they tend to develop cracks and deformations over time due to cyclic temperature changes experienced under high temperature operating conditions. In the case of carburizing furnace equipment, thermal stresses induced by the temperature gradient in each operating cycle on rapidly cooled elements have a significant influence on the progressive fatigue changes. In the carburized subsurface zone, also the different thermal expansion of the matrix and non-metallic precipitates plays a significant role in stress distribution. This article presents the results of analyses of thermal stresses in the surface and subsurface layer of carburized alloy during cooling, taking into account the simultaneous effect of both mentioned stress sources. The basis for the stress analyzes were the temperature distribution in the cross-section of the cooled element as a function cooling time, determined numerically using FEM. These distributions were taken as the thermal load of the element. The study presents the results of analyses on the influence of carbide concentration increase on stress distribution changes caused by the temperature gradient. The simultaneous consideration of both thermal stress sources, i.e. temperature gradient and different thermal expansions of phases, allowed for obtaining qualitatively closer results than analyzing the stress sources independently

Effects of yttrium on microstructures and properties of Cu45.12Zr45.12Al5.76Nb4 bulk metallic glass composites

The effects of yttrium on the microstructures and properties of Cu45.12Zr45.12Al5.76Nb4 bulk metallic glass composites were investigated. It was found that yttrium addition could effectively control the distribution and volume fraction of B2-CuZr precipitated phase in the composites by adjusting the glass-forming ability of the alloys, and suppress the eutectoid decomposition of B2-CuZr.Within 2 at.% yttrium addition, the volume fraction of B2-CuZr precipitation in the glassy matrix decreases significantly with the increase of yttrium content. For more than 2 at.% yttrium addition, the volume fraction of B2-CuZr precipitation increases as yttrium content increases. An optimal amount of yttrium (2–3 at.%) enhances glass-forming ability of the alloy, reduces B2-CuZr precipitation, and obviously improves the agglomeration and distribution uniformity of B2-CuZr in the amorphous matrix. The compressive properties of BMG composites with more than 1 at.% yttrium addition drop considerably, which should be mainly attributed to the abundant and various forms of Y2O3 brittle phase formed in the glassy matrix.

One-pot method for preparing DNA, RNA, and protein for multiomics analysis

Typical multiomics studies employ separate methods for DNA, RNA, and protein sample preparation, which is labor intensive, costly, and prone to sampling bias. We describe a method for preparing high-quality, sequencing-ready DNA and RNA, and either intact proteins or mass-spectrometry-ready peptides for whole proteome analysis from a single sample. This method utilizes a reversible protein tagging scheme to covalently link all proteins in a lysate to a bead-based matrix and nucleic acid precipitation and selective solubilization to yield separate pools of protein and nucleic acids. We demonstrate the utility of this method to compare the genomes, transcriptomes, and proteomes of four triple-negative breast cancer cell lines with different degrees of malignancy. These data show the involvement of both RNA and associated proteins, and protein-only dependent pathways that distinguish these cell lines. We also demonstrate the utility of this multiomics workflow for tissue analysis using mouse brain, liver, and lung tissue.

Comments on the Intermediate-Temperature Embrittlement of Metals and Alloys: The Conditions for Transgranular and Intergranular Failure

The intermediate-temperature embrittlement range was examined for Fe, Al, Cu, and Ni alloys. It was found that this embrittlement occurs in many alloys, although the causes are very diverse. Embrittlement can be due to fine matrix precipitation, precipitate free zones, melting of compounds at the grain boundaries, segregation of elements to the boundaries, and, additionally for steel, the presence of the soft ferrite film surrounding the harder austenite matrix. Grain boundary sliding and segregation to the boundaries seem to dominate the failure mode at the base of the trough when intergranular failure takes place. When cracking is due to the presence of hydrogen or liquid films at the boundary, then the dissociation along the boundaries is so easy, it is often independent of the strain rate and is always intergranular. In the other cases when failure occurs, if the deformation is carried out at a high strain rate, it is normally transgranular (e.g., hot rolling giving rise to edge cracking). However, when the strain rate is reduced to that of creep (e.g., bending during continuous casting of steel), failure can also take place by grain boundary sliding, and intergranular failure then becomes the favoured mode.

Evolution from clusters to precipitates in niobium-micro-alloyed ferritic steel: A combined in situ scanning transmission electron microscopy and atomistic study

Nano-sized carbides are essential for strengthening steel. In this study, we examined the evolution of metal carbide (M-C) clusters (M = Ti and Nb) into MC precipitates within a ferrite matrix through a reverse Bain transformation at the atomic level using the first-principles method. Through in situ transmission electron microscopy, the evolution of the Nb-C cluster into an NbC precipitate was observed for the first time. The Nb-C cluster was confirmed to maintain coherence with a limited carbon content, assuming a disc-shaped form that grew in a specific direction owing to misfit strain upon reaching a critical size. Interface dislocations were also formed. The NbC precipitate formation was subsequently completed through additional carbon diffusion. The findings of this study indicate that MC precipitation in a ferrite matrix can be attained through coherent cluster evolution with a specific carbon content.

First-principles study on the high-strength and high-conductivity modification mechanism of C7035 copper alloy by Ni, Si, and Co solid solution

In order to investigate the effects of matrix solid solution, precipitate phases, and microscale interfaces on the mechanical and electrical properties of copper alloys, we employed first-principles calculations based on density functional theory study aimed to understand how alloying elements enhance the strength and conductivity of copper. The results demonstrated that doping Co atoms into the copper matrix using the Dop2 structure model exhibited the most significant improvement in both mechanical and electrical properties. The Young's modulus was doubled compared to pure copper, and the hardness increased several times. The electrical conductivity reached 59.8 % of the International Annealed Copper Standard (IACS), showing a 6.6 % enhancement compared to Si doping. To validate computational results, we conducted experiments that confirmed the accuracy of the predicted mechanical and electrical properties. Furthermore, the introduction of Co effectively reduced electron losses at the interface between the precipitate phase and the copper matrix. The electron transmission rate through the Co2Si (211)/Cu (111) interface reached 78.6 %, representing a 94.1 % improvement compared to the Ni2Si (111)/Cu (111) interface. In conclusion, Co can simultaneously enhance the mechanical and electrical properties of Cu–Ni–Si alloys, providing theoretical guidance for the design and fabrication of high-strength and high-conductivity copper alloys.

Enhanced corrosion performance by controlling grain boundary precipitates in a novel crossover Al-Cu-Zn-Mg alloy by optimizing Zn content

The effect of Zn contents on grain boundary precipitates (GBPs), intergranular corrosion (IGC), and stress corrosion cracking (SCC) of crossover Al–Cu–Zn–Mg alloys was investigated. The increase in Zn contents accelerates the age-hardening response, and both matrix precipitates (MPs) and GBPs are transformed from S phase to S and η phases, while the width of the precipitates free zones (PFZs) first increases and then decreases. The narrowed PFZ width, coarse and discontinuous GBPs were able to inhibit anodic dissolution resulting in enhanced IGC resistance. The η phase inhibits anodic dissolution leading to an enhanced IGC resistance. First-principles calculations demonstrate that the GBPs surface with Mg termination planes shows a lower work function than that of Al leading to preferential anodic dissolution. The evolution of GBPs and PFZ widths changes the mechanism of SCC susceptibility for different Zn contents alloys from anodic dissolution and hydrogen embrittlement to anodic dissolution.

Degradation Mechanism Study for Secondary Degradants in Rosuvastatin Calcium and Determination of Degradant Acetaldehyde Using Static Headspace Gas Chromatography Coupled with Matrix Precipitation

During the development of headspace gas chromatography (HSGC) method for assessing residual solvents in rosuvastatin calcium (RSV) drug substance, acetaldehyde (AA) was detected in obtained chromatograms, with a calculated concentration of up to 226 ppm. After a series of experiments, it was established that acetaldehyde originates from matrix interference due to direct degradation of Imp-C, which is accompanied by the formation of impurity at relative retention time (RRT) 2.18, without the involvement of impurity at RRT 2.31. The thermal instability of Imp-C also results in the formation of impurity at RRT 2.31 through dehydration and decarboxylation. In addition, cyclization reaction of degradant at RRT 2.18 further resulted in the generation of impurity at RRT 2.22. The structure of these three degradants, were confirmed by liquid chromatography-mass spectrometry (LC-MS), 1D and 2D nuclear magnetic resonance (NMR) measurement. In order to minimize the said matrix interference, a simple precipitation procedure was proposed as a pretreatment to mitigate the impact of Imp-C. Subsequently, an HSGC method was developed for the simultaneous determination of the degradant AA and the other five residual solvents used in RSV synthetic process. The final method was validated concerning precision, limit of detection (LOD) and limit of quantitation (LOQ), linearity, and accuracy.

Study on casting simulation and wear properties of honeycomb configuration ZTAp-Fe composite

The primary objective of this research is to develop a honeycomb configuration ZTAp-Fe composite, with varying concentrations of ZTAp (zirconia-toughened alumina particles) at 5 wt%, 10 wt%, and 15 wt%, to address wear-related issues in mining machinery components. A numerical simulation of the casting process to study the temperature field variation in composites and gravity casting was subsequently performed using 30SiMn steel liquid. A comprehensive examination of the composite's characteristics was conducted, employing XRD, SEM, EDS, three-body abrasive wear, and scratch testing. The study revealed a metallurgical bonding between the interface of 30SiMn steel and the iron matrix, characterized by a fusion zone with a width of approximately 182 μm. Furthermore, the honeycomb configuration of the preform was found to enhance heat transfer during the casting process. Both 30SiMn steel and the iron matrix exhibited a room temperature organization of α-Fe, and the micron granular precipitates in the iron matrix are (Fe, Cr)7C3. However, it was observed that when the ZTAp content reached 15 wt%, particle accumulation hindered heat transfer, which led to pore defects, resulting in poor mechanical bonding between ZTAp and the iron matrix. Compared to various three-body abrasive wear loads (50 N, 90 N, and 130 N), the wear properties initially improved with an increase in ZTAp content from 5 wt% to 15 wt% but then weakened. The presence of hard-phase ZTAp was found to play a significant role in blocking scratches, and composites with 10 wt% ZTAp content exhibited excellent wear properties.

Influences of partial substitution of C by N on the microstructure and mechanical properties of 9Cr18Mo martensitic stainless steel

Large eutectic carbides presenting in the matrix deteriorate the mechanical properties of high carbon martensitic stainless steel. In the present work, nitrogen-alloyed martensitic stainless steel with different C/N ratios were designed by partial substitution of C by N of 9Cr18Mo, and their microstructure and mechanical properties were investigated. The results show that, with increasing the content of N up to 0.15 wt% in the experimental steel, the quantity and the size of eutectic carbides decrease； and the net-work eutectic carbides are gradually eliminated. The microstructure of all the steels is composed of lath martensite, twin martensite and M23C6 carbides. With partial substitution of C by N, the morphology of martensite blocks evolves from a lath shape to a blocky one, the quantity of twin martensite increases, and the nano-scaled Cr2N nitrides precipitate in the martensite matrix. The steel containing 0.15 wt% N exhibits the hardness of 60.5 HRC, a fracture strength of 1900 MPa and an elongation rate of 1.6 % due to hot rolling and heat treatment, which is attributed to the refinement of carbides and grains, solid solution of C and N, as well as the dense dislocation.