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At least 145 records · Page 8

Effect of Solution Treatment on the Microstructure, Micromechanical Properties, and Kinetic Parameters of the β → α Phase Transformation during Continuous Cooling of Ti-6Al-4V Titanium Alloy

The aim of this study is to examine the effect of solution treatment temperature (STT) on the microstructure, the micromechanical properties, and the kinetic parameters of the β → α phase transformation during continuous cooling of the dual phase titanium alloy Ti-6Al-4V. Increasing the STT from 1050 to 1200 °C delays the formation of the α phase during cooling and increases the value of its activation energy. The microstructural analysis reveals the emergence of α{sub W} platelets from protuberances on the α{sub GB}/α{sub W} interface. The investigation of the morphology of the α{sub W} platelets reveals the presence of ledges on their longest side showing a sharp extremity. The micromechanical properties determined by nanoindentation and microhardness tests are almost insensitive to the cooling rate but are strongly affected by the STT; the higher the STT, the lower the overall microhardness of the Ti-6Al-4V alloy. In addition, the STT affects the microhardness and the Young’s modulus of both α and β phases differently; when the STT increases, the microhardness and the Young’s modulus of the α phase decrease, whereas those of the β phase increases.

36 MATERIALS SCIENCE↗

Predicting melt pool depth and grain length using multiple signatures from in-situ single camera two-wavelength imaging pyrometry for laser powder bed fusion

In laser powder bed fusion (LPBF), the in-situ process signatures are known to have a direct correlation with the microstructural properties of the solidified melt pool (MP). It is known that the MP cooling and heating rates, and laser processing parameters can critically determine the grain structure and thereby affect the part properties. The objective of this work is to study the feasibility of using in-process, high-speed imaging pyrometry for evaluating the solidified MP properties “below” the surface, such as depth and microstructural properties. To accomplish this, we employ an in-house single camera-based two-wavelength imaging pyrometry (STWIP) system for monitoring the printing of single-scan tracks with Inconel 718 on a commercial LPBF printer (EOS M290). Further, the lab designed STWIP system is a coaxial high-speed (>10,000 fps) imaging system capable of monitoring MP temperature, morphology, and intensity profiles. The temperature measurements from STWIP are emissivity independent. The STWIP measured MP signatures of the printed tracks are correlated with the ex-situ microscopy characterized MP depth and the average grain lengths. From the data analysis, using support vector machine (SVM)-based regression models, we found that the MP temperature signatures are crucial for an accurate prediction of MP depth and the grain length, thus validating the novelty and necessity of the developed in-situ monitoring methods and analysis.

36 MATERIALS SCIENCE↗

High-Temperature Properties and Microstructural Stability of the AISI H13 Hot-Work Tool Steel Processed by Selective Laser Melting

The microstructural stabilities, softening resistance, and high-temperature tensile properties of the H13 hot-work tool steel by selective laser melting (SLM) were systematically studied. A series of tempering procedures were performed on the as-SLMed specimens. Afterwards, the mechanism of softening resistance behavior was discussed based on the XRD, SEM, EBSD observations, hardness measurements, and high-temperature tensile tests. It was found that the as-SLMed H13 consisted of α-iron and γ-iron. The carbide-stabilizing elements aggregated as the cell-like substructures for the rapid solidification of the SLM process. After the softening resistance treatment, the retained austenite transformed to ferrite and carbide mixtures. The cell-like substructures dissolved slowly into the matrix when the temperature was below 550 °C. These factors increased the hardness and retarded the softening of the material. When the temperature was 600 °C, the microstructural constituents transformed to soft ferrite and globular carbides, which lead to a considerable decrease of the hardness. Due to the grain refinement, solid solution strengthening, and residual stress, the as-SLMed H13 exhibited better mechanical properties than that of the wrought counterparts.

36 MATERIALS SCIENCE↗

Fracture properties and microstructure formation of hardened alkali-activated slag/fly ash pastes

This study presents a comprehensive experimental investigation on the fracture properties of hardened alkali-activated slag/fly ash (AASF) pastes in relation to the microstructure formation and reaction product composition. The main reaction product in AASF is C-(N-)A-S-H gel along with minor hydrotalcite phase, with the polymerization of C-(N-)A-S-H gel substantially governed by its Ca/Si ratio. Strong positive correlations are identified between the Ca/Si ratios of C-(N-)A-S-H gel and the fracture properties K{sub Ic} (J{sub tip}), whereas, the compressive strength of AASF pastes is primarily determined by its capillary porosity (>0.01 μm). The disagreements between the Ca/Si ratios and corresponding intrinsic mechanical properties of C-(N-)A-S-H gel as proof by contradiction indicate that the fracture properties K{sub Ic} (J{sub tip}) of AASF pastes could be dominated by a cohesion/adhesion-based mechanism. These findings provide promising guidance for fine-tuning the fracture properties of AASF and also advise on the tailoring strategies for high-performance composite such as strain-hardening geopolymer composite.

36 MATERIALS SCIENCE↗

ML-based Micro-CT SOFC Microstructure Models (from Kent 2026 Microstructural Augmentation paper)

Overview -------------------------- This repository contains datasets from the manuscript **"Enhanced Generalizability to Deep-Learning Quantification of 3D Microstructural Characteristics through Microstructurally Aware Augmentation of Scarce Data"** (*William F. Kent, Rochan Bajpai, Rachel C. Kurchin, William K. Epting, Harry W. Abernathy, Paul A. Salvador. Submitted 2026*). The methods are also described in the dissertation **Data Intensive Analysis of Solid Oxide Cell Microstructures** (*Doctoral dissertation, Carnegie Mellon University, 2025*). The datasets here are trained convolutional neural network (CNN) models for predicting key microstructural properties of solid oxide cell (SOC) electrodes from low-res, 2-channel 3D images, as well as some helpful code. The parameters for input images are provided in the paper. Sample data is provided in the file `Combined_anode_aug_dual_1k_examples` - that particular data was used to train `anode_all_aug.pth` and will work most accurately with that model. Please familiarize yourself with all caveats on accuracy and applicability, as detailed in the associated paper. Usage -------------------------- The basic usage is as follows, assuming `model_fn` is the path to the .pth file, and `X` is 2-channel input image(s) of the proper dimensions (either one image of shape `[2,12,24,24]`, or a batch of N input images of shape `[N,2,12,24,24]`): from CNN_inferencer import load_model_for_inference model = load_model_for_inference(model_fn) y_predicted = model(X) The model object automatically handles input scaling and output de-scaling based on the way the models were trained - in other words, pass in a 2-channel micro-CT image, and it will output microstructural property values in real units. ## Other model object attributes Note that model has useful attributes other than its forward pass model(X). * `model.output_descaler` - returns the output descaler object. Model does the de-scaling when generating inferences, but you may want to re-use this de-scaler on other values to e.g. compare predictions to ground truth from already-scaled training data. * `model.prop_names` - Gives the property names of the predicted y values, in order. Only exists if there's an output scaler as part of the model object, which there will be in the models provided here. ## Usage with sample data Here is a short script to use with the included sample data. from CNN_inferencer import display_predictions, load_model_for_inference, calculate_mape, parity_plot import h5py import numpy as np model_fn = 'anode_all_aug.pth' data_fn = 'Combined_anode_aug_dual_1k_examples.h5' N_samples = 200 figure_outdir = '.' model = load_model_for_inference(model_fn) with h5py.File(data_fn,'r') as f: XX = f['X'] #These are the 2-channel 3D images yy = f['y'] #These are the ground-truth microstructural properties, but they have been scaled for training - need to de-scale below N = XX.shape[0] #How many images total in the input data file #Run inferences on N_samples random samples from XX. #Run in a batch, much more efficient than one at a time. ii = np.random.choice(N,N_samples,replace=False) ii.sort() y_pred = model(XX[ii]) #Get the original/true (but normalized/scaled) values from the training dataset... #Because they were normalized, they are not in real units yet. So let's also de-scale them using model.output_scaler. y_true = model.output_scaler.transform(yy[ii]) #Let's display actual values for just 5 random ones for i in np.random.choice(N_samples,5,replace=False): display_predictions(y_true[i], y_pred[i], model.prop_names) #Make parity plots for each property (ground truth vs predicted values) #Also label each plot with the mean abs. percent error (MAPE) of the predicted values for i,key in enumerate(model.prop_names): mape = calculate_mape(y_true[:,i], y_pred[:,i]) parity_plot(y_true[:,i], y_pred[:,i], figure_outdir, key, extra_title=f' ({mape:.2f}% MAPE)')

3D microstructure↗

Tensile Properties and Microstructural Characterization of Hi-Nicalon SiC/RBSN Composites

The room temperature physical and mechanical properties of silicon carbide fiber-reinforced reaction-bonded silicon nitride matrix composites (SiC/RBSN) were measured, and the composite microstructure was analyzed. The composites consist of nearly 24 vol% of aligned Hi-Nicalon SiC fiber yarns in a approx. 30 vol% porous silicon nitride matrix. The fiber yarns were coated by chemical vapor deposition with a 0.8 mm layer of boron nitride (BN) followed by a 0.2 mm layer of SiC. In the as-fabricated condition, both 1-D and 2-D composites exhibited high strength and graceful failure, and showed improved properties w en compared with unreinforced matrix of comparable density. No indication of reaction between the SiC fiber and BN coating was noticed, but the outer SiC layer reacted locally with the nitridation enhancing additive in the RBSN matrix. A comparison is made between the predicted and measured values of matrix cracking strength.

Bhatt, Ramakrishna T.↗

Tensile Properties and Microstructural Characterization of Hi-Nicalon SiC/RBSN Composites

The room temperature physical and mechanical properties of silicon carbide fiber-reinforced reaction-bonded silicon nitride matrix composites (SiC/RBSN) were measured, and the composite microstructure was analyzed. The composites consist of nearly 24 vol% of aligned Hi-Nicalon SiC fiber yarns in a approx. 30 vo1% porous silicon nitride matrix. The fiber yarns were coated by chemical vapor deposition with a 0.8 micron layer of boron nitride (BN) followed by a 0.2 micron layer of SiC. In the as-fabricated condition, both 1-D and 2-D composites exhibited high strength and graceful failure, and showed improved properties when compared with unreinforced matrix of comparable density. No indication of reaction between the SiC fiber and BN coating was noticed, but the outer SiC layer reacted locally with the nitridation enhancing additive in the RBSN matrix. A comparison is made between the predicted and measured values of matrix cracking strength.

Bhatt, Ramakrishna T.↗

A Study on the Microstructures and Properties of Selective Laser Melted Babbitt Metals

Babbitt metal cubes were prepared by means of selected laser melting (SLM) process using Sn—11% Sb—6% Cu alloy powders; their microstructures were studied using optical microscope (OM), SEM, EDS, XRD and DSC; and their mechanical properties were tested using Vickers hardness and tensile methods. The results show that fully dense Babbitt metal components can be prepared by using appropriate SLM process parameters and an interlayer staggered laser scanning strategy. Anisotropy characteristics appear in both the microstructure and mechanical properties of SLM-Babbitt cubic specimens. The average hardness was in the range of 32.5 HV0.05 to 35.3 HV0.05. Both tensile strength and elongation were somewhat higher in a direction parallel to the laser scanning speed (Y axis) than in a direction perpendicular to the laser scanning speed (X axis). The strengthening mechanism is suggested to include solid solution strengthening of oversaturated Sb in the Sn matrix, as well as dispersion strengthening of finely dispersed SnSb and Cu{sub 6}Sn{sub 5} particles. The overgrown acicular Cu{sub 6}Sn{sub 5} phases at low laser scanning speeds and void formation at higher laser scanning speeds seriously deteriorate the mechanical properties of the SLM-Babbitt specimens.

36 MATERIALS SCIENCE↗

Property and microstructural nonuniformity in the yttrium-barium-copper-oxide superconductor determined from electrical, magnetic, and ultrasonic measurements

The purpose of this dissertation was the following: (1) to characterize the effect of pore fraction on a comprehensive set of electrical and magnetic properties for the yttrium-barium-copper-oxide (YBCO) high temperature ceramic superconductor; and (2) to determine the viability of using a room-temperature, nondestructive characterization method to aid in the prediction of superconducting (cryogenic) properties. The latter involved correlating ultrasonic velocity measurements at room temperature with property-affecting pore fraction and oxygen content variations. The use of ultrasonic velocity for estimating pore fraction in YBCO is presented, and other polycrystalline materials are reviewed, modeled, and statistically analyzed. This provides the basis for using ultrasonic velocity to interrogate microstructure. The effect of pore fraction (0.10-0.25) on superconductor properties of YBCO samples was characterized. Spatial (within-sample) variations in microstructure and superconductor properties were investigated, and the effect of oxygen content on elastic behavior was examined. Experimental methods used included a.c. susceptibility, electrical, and ultrasonic velocity measurements. Superconductor properties measured included transition temperature, magnetic transition width, transport and magnetic critical current density, magnetic shielding, a.c. loss, and sharpness of the voltage-current characteristics. An ultrasonic velocity image constructed from measurements at 1mm increments across a YBCO sample revealed microstructural variations that correlated with variations in magnetic shielding and a.c. loss behavior. Destructive examination using quantitative image analysis revealed pore fraction to be the varying microstructural feature.

Roth, Don J.↗

Influence of Thermal Treatment on the Microstructure, Mechanical Properties, and Corrosion Resistance of Newly Developed Ti20Nb13Zr Biomedical Alloy in a Simulated Body Environment

The effect of thermal treatments on the microstructure, hardness, and electrochemical performance in a simulated body fluid were studied for the newly developed (β + α) Ti20Nb13Zr alloy (TNZ) for biomedical applications. The alloy was heat-treated for 1 h at 900 °C and then cooled at different cooling rates. Then, the solution-treated samples were aged at 400, 500, or 600 °C for 5 h. The phase evolution and microstructure of the treated alloy were examined using XRD and SEM/EDX analysis. The mechanical properties were assessed using microindentation. The surface protection performance against corrosion was assessed by potentiodynamic polarization and electrochemical impedance spectroscopic analysis. The obtained results showed that the wide range of microstructure with varied volume fraction and morphology of β and α were obtained with different heat treatment conditions. The different phases’ sizes and distributions influenced the microstructure obtained during the heat treatment, thereby affecting the mechanical properties. The corrosion performance significantly altered with variations in the microstructure of the TNZ alloy as a result of the different thermal treatments. The heat treatment of TNZ conferred enhanced combination of mechanical and corrosion protection compared to that of the commercial Ti6Al4V alloy.

36 MATERIALS SCIENCE↗

Effect of the Laser Scan Rate on the Microstructure, Magnetic Properties, and Microhardness of Selective Laser-Melted FeSiB

FeSiB alloys have been fabricated by selective laser melting (SLM) using a laser scan rate of 0.1–1.5 m/s, laser power of 90 W, scan line spacing of 40 μ m, and layer thickness of 50 μ m. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, profilometer, microdurometer, and vibrating sample magnetometer have been used to investigate the structural, microstructural, roughness, microhardness, and magnetic property changes during the laser melting process. The produced samples exhibit a nanocomposite structure consisting of nanocrystalline α-Fe{sub 0.95}Si{sub 0.05} and Fe{sub 2}B phases embedded into an amorphous ε-FeSi-type matrix. The selective laser-melted samples show high density, low surface roughness, higher microhardness values (1654–2273 Hv), and soft magnetic properties (M{sub s} = 188.6–199 emu/g and H{sub c} = 43.8–73 Oe).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Processing, Microstructure, and Properties of Bimetallic Steel-Ni Alloy Powder HIP

This work explores technical feasibility in hot isostatic pressing (HIP) manufacturing of an integral bimetallic component using steel and Ni alloy powder for supercritical carbon dioxide (sCO2) turbomachinery. Lab-scale bimetallic HIP specimens using HAYNES® 282® and SS316L or SS415 powder are investigated in powder configuration, heat treatment, microstructure, and tensile properties up to 400 °C. Interdiffusion profiles at dissimilar alloy interfaces caused by HIP cycle is predicted by DICTRA simulations and validated by electron probe microanalysis (EPMA). The interdiffusion distance of most elements is around 100 μm, while C and N have a higher interdiffusion distance. Dense distribution of Ti-rich carbonitrides and alumina particles are found to decorate prior particle boundaries near joining interface on the 282 side, affecting tensile strength across interface as well as tensile failure location. A higher amount of excessive carbonitride formation near interface is observed in SS316L/282 than in SS415/282, which is consistent with the predicted greater degree of interdiffusion effect in SS316L/282. Typical HAYNES® 282® heat treatment condition is applicable to 282/SS316L and 282/SS415 combinations, resulting in a higher strength than cast CF8M and CA6NM. A pilot-scale bimetallic SS415/282 pipe is then demonstrated to show the promise of scaleup.

36 MATERIALS SCIENCE↗

Alloying effects on the microstructure and properties of laser additively manufactured tungsten materials

A large body of literature within the additive manufacturing (AM) community has focused on successfully creating stable tungsten (W) microstructures due to significant interest in their application for extreme environments. However, cracking and additional embrittling features at grain boundaries have resulted in poorly performing materials, stymying the application of AM as a manufacturing technique for W. Several alloying strategies, such as ceramic particles and ductile elements, have emerged with the promise to eliminate cracking while simultaneously enhancing stability against recrystallization. Here, in this work, we provide new insights regarding the defects and microstructural features that result from the introduction of ZrC for grain refinement and NiFe as a ductile reinforcement phase – in addition to the resulting thermophysical and mechanical properties. ZrC is shown to promote microstructural stability with increased hardness due to the formation of ZrO 2 dispersoids. Conversely, NiFe forms into micron-scale FCC phase regions within a BCC W matrix, producing enhanced toughness relative to pure AM W. A combination of these effects is realized in the WNiFe + ZrC system and demonstrates that complex chemical environments coupled with the tuning of AM microstructures provides an effective pathway for enabling laser AM W materials with enhanced stability and performance.

36 MATERIALS SCIENCE↗

Effect of LID (Registered) processing on the microstructure and mechanical properties of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo titanium foil-gauge materials

A study was undertaken to determine the mechanical properties and microstructures resulting from Liquid Interface Diffusion (LID -Registered) processing of foil-gauge specimens of Ti-6Al-4V and Ti-6Al-2Sn-4Zr-2Mo coated with varying amounts of LID material. In addition, the effects of various elevated temperature exposures on the concentration profiles of the LID alloying elements were investigated, using specimens with a narrow strip of LID material applied to the surface. Room and elevated temperature tensile properties were determined for both coated and uncoated specimens. Optical microscopy was used to examine alloy microstructures, and scanning electron microscopy to examine fracture surface morphologies. The chemical concentration profiles of the strip-coated specimens were determined with an electron microprobe.

Balckburn, Linda B.↗

Effects of Heat Treatment Parameters on the Microstructure and Properties of Bainitic Steel

The results obtained in the present study demonstrate the effects of various types of heat treatment processes on the microstructure and hardness of new trip-assisted carbide-free bainitic steel. The steel was subjected to three variants of heat treatment processing with an isothermal bainitic transformation temperature in a range from 350 to 480 °C. Changes of temperature and time of isothermal holding caused changes in the values of retained austenite (RA) volume fraction and carbon content. Reduction in the isothermal holding temperature resulted in the increased concentration of carbon in austenite. Also, the investigations of the microstructure showed that size and morphology of the austenite evolved during heat treatment. The SEM observations revealed that the steel subjected to heat treatment is composed of the carbide-free bainite with ferrite plates and a high volume fraction of retained austenite in the form of thin layers or islands. With the lower isothermal holding temperature and the higher degree of bainitic transformation, the more the RA morphology changed from island to layer type. The application of the lowest isothermal temperature resulted in a significant refinement of the microstructure components: the bainitic ferrite plates and the RA layers. Also, the mechanical properties obtained from the tensile testing and hardness measurements were correlated to the microstructure of the investigated steel after different isothermal holdings.

36 MATERIALS SCIENCE↗

Microstructure and Properties of A356 Alloy Wheels Fabricated by Low-Pressure Die Casting with Local Squeeze

The low-pressure die-casting process (LPDC) is widely used in fabricating aluminum alloy automotive wheels. With good castability and mechanical properties, A356 alloys are important and common materials for LPDC wheels. However, in practical casting process, defects often appear, especially porosities in the wheel thick-walled parts (i.e., spoke) due to inadequate interdendritic feeding, which greatly decreases the mechanical properties. In this investigation, to deal with this problem, local squeeze (LS) was added in conventional LPDC to enhance the interdendritic feeding. The practical A356 alloy wheel castings were fabricated with different LS velocities and times. The quantitative characteristics of α-Al cells, Si particles, and porosities with and without the LS analyzed by optical microscope, scanning electron microscope, and 3D x-ray computed tomography were compared. Their effects on the tensile and impact properties were discussed. The results have shown that the LS can increase the cooling rate and feed shrinkage of spoke parts, hence resulting in finer grains and denser microstructure. In result, the properties of spoke parts were improved with the LS.

36 MATERIALS SCIENCE↗

Microstructure and Properties of Inconel 718 Fabricated by Directed Energy Deposition with In-Situ Ultrasonic Impact Peening

Many inherent issues, such as the detrimental residual stress, columnar grains with anisotropy, and weak mechanical properties, have severely impeded the adoption of metal additive manufacturing (AM) techniques including powder bed fusion and directed energy deposition (DED) processes. In this study, a hybrid AM process that consists of layer-wise laser metal deposition (i.e., a DED process) and in-situ ultrasonic impact peening (UIP) was applied to obtain Inconel 718 superalloy workpieces. Also, for further property enhancement, a post-heat treatment was applied to the deposited material obtained by the hybrid AM process. Scanning electron microscopy and transmission electron microscope were used to investigate the microstructure morphology and reveal the underlying strengthening mechanism. Electron backscatter diffraction was employed to quantitatively study the microstructure resulted from the hybrid AM process and the post-heat treatment. The profile of residual stress along the depth direction was obtained through X-ray diffraction. The results demonstrate that this hybrid AM process is capable of producing high-quality metal parts with significantly refined microstructure, and beneficial compressive residual stress along the depth into surface. Severe plastic strains are introduced by UIP, and the resulted mechanical twinning and dynamic recrystallization play an important role in refining microstructure. The material microstructure is further refined down to 100 µm, and the texture anisotropy is significantly diminished after solution treatment at 980 °C for 1 hour. Under the as-built condition, in-situ ultrasonic peening alters the residual stress component from a tensile state to an overall compressive state with a maximum value of − 190 MPa within the range of measurement depth.

36 MATERIALS SCIENCE↗

Microstructure and Mechanical Properties of Spray-Formed 7075 Alloy During Retrogression

The mechanical properties, conductivity, microstructure, precipitation behavior and evolution process of elements and phases of spray-formed 7075 alloy during retrogression are studied by the tensile test, electric test, hardness test, transmission electron microscope (TEM), x-ray diffraction (XRD) analysis, electron-dispersive spectroscopy (EDS) and lattice parameter measurements. The results show that the mechanical properties and conductivity of the alloy can be effectively improved when treated at a suitable retrogression temperature and time. According to the TEM observations, XRD analysis, EDS and an accurate measurement of the lattice parameter, the redissolution of elements and precipitated phases can be readily observed. From the optimization selection of the RRA treatment for the 7075 alloy, the regularity of redissolution and precipitation of the elements and phases are evaluated. The ultimate tensile strength, yield strength, hardness, elongation and conductivity of the spray-formed 7075 alloy after preaging at 120 °C for 16 h, retrogression at 200 °C for 8 min and reaging at 120 °C for 24 h are 791, 736 MPa, 181 HBW, 8.5% and 22.6 MS/m, respectively.

36 MATERIALS SCIENCE↗