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Similar Journals
 Metals and Materials InternationalJournal Prestige (SJR): 0.724 Citation Impact (citeScore): 2Number of Followers: 1      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1598-9623 - ISSN (Online) 2005-4149 Published by Springer-Verlag  [2469 journals]
• Matrix Channel Width Evolution of Single Crystal Superalloy Under Creep
and Thermal Mechanical Fatigue: Experimental and Modeling Investigations

Abstract: In this study, in the respect of rafting behavior of Ni-based single crystal (SC) superalloy under creep and thermal mechanical fatigue (TMF), an image processing program is developed to investigate the probability characteristic of γ channel width, and a channel width evolution model considering non-quasi-static modification is proposed. Firstly, the fractured and interrupted tests are conducted on SC superalloy. The channel width evolution behavior under different load conditions is observed via scanning electron microscope. Then, an image processing program based on image binarization is developed to conduct statistics on channel width. The statistical results show that the stress and temperature have significant effects on rafting rate, while the phase difference has a small effect. Meanwhile, the channel width obeys lognormal distribution, and the mean values follow linear relationship with standard deviations. In the modeling part, a static model is established to predict the mean value evolution of channel width under creep condition. To be generalized to TMF condition, the model is modified by considering the non-quasi-static effect. After that, the channel width evolution model is further derived to describe the probability density distribution of channel width. The predicted channel width evolutions are in good agreement with the experimental results. The statistical results and models can provide the basis for multiscale modeling of SC superalloy. Graphic
PubDate: 2022-05-24

• Inclusion Agglomeration on Ultra-Low C Liquid Steel Surface: Roles of Ti
in the Steel and the Oxygen Potential

Abstract: Behavior of inclusions as particles on liquid Ultra-Low C (ULC) steel was investigated both by an in-situ observation and a theoretical analysis. The behavior was examined in view of Ti content in the steel as an alloying component and of oxygen potential exerted on the surface of the steel melt. A confocal scanning laser microscopy with a gold image furnace was used for the observation, and the force exerted between two particles was extracted. It was found that the inclusions showed attraction each other, and agglomerated. When the oxygen potential was low ( $$P_{\mathrm{O}_2} \simeq 10^{-22}$$ bar), the presence of Ti ( $$[\%\ \text{Ti}] = 0.0735$$ ) did not influence on the agglomeration force as well as the acceleration. However, increasing $$P_{\mathrm{O}_2}$$ ( $$\simeq 10^{-15}$$ bar) resulted in slight decrease of the acceleration. When Ti content was very low ( $$[\%\ \text{Ti}] =0.0018$$ ), $$P_{\mathrm{O}_2}$$ did not influence the attraction. A post-mortem analysis of the inclusion composition revealed that the inclusions on the Ti-free steel surface were mostly alumina regardless of the $$P_{\mathrm{O}_2}$$ employed in the present study, while those on the Ti-added steel were composed of $$\text{Fe}_t\text{O}$$ – $$\text{Al}_2\text{O}_3$$ (low $$P_{\mathrm{O}_2}$$ ) or $$\text{Fe}_t\text{O}$$ – $$\text{TiO}_x$$ (– $$\text{Al}_2\text{O}_3$$ ) (high $$P_{\mathrm{O}_2}$$ ). From the analysis using Kralchevski-Paunov model for lateral capillary force between two spherical particles, it is suggested that the formation of $$\text{Fe}_t\text{O}$$ -containing oxidation product lowers the contact angle between the inclusion and the liquid steel, thereby lowering the agglomeration force as well as the acceleration. However, the model generally underestimated the agglomeration force. Graphical abstract
PubDate: 2022-05-21

• Effect of Intercritical Heat Treatment on J-R Fracture Resistance of SA508
Gr.1A Low-Alloy Steels

Abstract: SA508 Gr.1A low-alloy steel is used for main steam line piping in nuclear power plants. The yield strength and J-R fracture resistance of the piping material must be high in order to apply the leak-before-break concept. In this study, intercritical heat treatment (IHT) was applied to two SA508 Gr.1A low-alloy steels having different chemical compositions, namely, samples C and P; the latter containing Mo and V. Their microstructures, tensile properties, impact properties, and J-R fracture resistances were evaluated, and the effects of IHT on the mechanical properties of the steels were analyzed. After IHT, fine grains formed at grain boundaries and coarse cementite decomposed, which greatly improved toughness without reducing the strength. Further, a model to predict the J-R fracture resistance (JIc) of the SA508 Gr.1A low-alloy steel was developed by considering the microstructural and mechanical factors that affect the J-R fracture resistance. According to the JIc results of 12 kinds of SA508 Gr.1A low alloy steel, subjected to different heat treatments, the JIc was linearly proportional to the number of effective grains (N) contained in the plastic zone, which showed that N is the main factor affecting JIc. Furthermore, the yield and tensile strengths were considered to compensate for the strength difference owing to the different chemical compositions. The JIc prediction model was derived considering the effective grain size, plastic zone size, and tensile properties. The predicted JIc values agreed well with the test JIc values. Graphical abstract
PubDate: 2022-05-20

• Texture Evolution of Hot Rolled Al–Cu–Mg–Zr Alloy During
Annealing

Abstract: Texture growth and relative mechanism of Al–Cu–Mg–(Zr) alloy during annealing have been investigated by three dimensional Orientation Distribution Functions (ODFs), Electron Back Scattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM). The results show that Zr addition in Al–Cu–Mg alloy restricts the preferable growth of recrystallized Goss grain, and fails to improve the total intensity of Goss texture. Recrystallized Goss is difficult to nucleate within Brass orientation even after full recrystallization, and Copper and S grains cannot preferably transform into Cube grains in Al–Cu–Mg–Zr alloy. Instead, the growth of random textures is favorable at the expense of deformed Brass, Copper and S textures. These phenomena can be well explained by relating to the disappearance of Σ5, Σ7 and Σ9 boundaries caused by Al3Zr pinning dislocation. In addition, it is found that the Brass texture of Al–Cu–Mg–Zr alloy can be enhanced at specific annealing temperature, which is attributed to the formation of recrystallized Brass grains. Lastly, the deformed Goss of Al–Cu–Mg–Zr alloy is energy-unstable as compared with Brass during annealing, and these deformed Goss grains will subsequently evolve into recrystallized Brass or random orientations. Graphical
PubDate: 2022-05-20

• Thermal Stability of Precipitates in Al-2.8 wt%Cu-1.4 wt%Li
Alloy

Abstract: The microstructures and mechanical properties of Al-2.8 wt%Cu-1.4 wt%Li-T87 alloy after thermal exposure at 125, 150 and 175 °C were measured and characterized by universal testing machine, scanning electron microscope and transmission electron microscope. The thermal stability of microstructures and mechanical properties of T87 heat-treated Al-2.8 wt%Cu-1.4 wt%Li alloy was investigated. The results show that the tensile strength of Al-2.8 wt%Cu-1.4 wt%Li-T87 alloy increased first and then decreased with the increase of thermal exposure temperature, which is due to the change of the number and size of precipitates. After thermal exposure at 125 °C, the alloy exhibited higher strength due to further precipitation of θ′ phase and stable size of T1 phase. After thermal exposure at 175 °C, the mechanical properties of Al-2.8 wt%Cu-1.4 wt%Li-T87 alloy decreased obviously, which was related to the dissolution of θ' phase and thickening of T1 phase. Graphic abstract
PubDate: 2022-05-19

• Influence of Heat Treatment on Microstructure and Mechanical Properties of
TC4 Fabricated by Laser Melting Deposition

Abstract: The phase composition, microstructure, tensile properties of TC4 samples produced by laser melting deposition (LMD) and LMD followed by solution-aging treatment were investigated to explore a simpler approach to improve the mechanical performances and eliminate negative influences by post treatment. The as-deposited TC4 microstructure showed a combination of α΄martensite and α-colony with various shapes, such as acicular, rod-like and lamellar. As a synergistic result of solution and aging treatment, the dispersion strengthening of secondary-α as well as optimization on length-width ratio of primary-α and volume fraction of β-phase cause an increase in the ductility and strength. Meanwhile, there is a difference between microstructure of water-quenched specimens and air-cooled specimens, subsequently playing a key role in properties. The solution with air-cooling and aging is comparatively found to significantly reduce the anisotropy and improve comprehensive performance. Graphical
PubDate: 2022-05-18

• Ti6Al4V/SiC Metal Matrix Composites Additively Manufactured by Direct
Laser Deposition

Abstract: Nowadays, research on additive manufacturing of Ti6Al4V alloy is growing exponentially but there are just a few studies about additive manufacturing of metal matrix composite components. In this work, highly reinforced Ti6Al4V matrix composites with SiC particles have been additively manufactured by direct laser deposition (DLD). Ti6Al4V powder and SiC particles have been deposited layer by layer to form an additive thin wall structure. The geometry, microstructure, and microhardness of the samples are strongly influenced by the laser scanning speed used during de fabrication process. In addition, the effect of the SiC increment in reinforcement concentrations and the influence of SiC particle sizes in the microstructure have been evaluated, and the reaction mechanisms have been established. The percentage of reinforcement measured is lower than expected due to the reinforcement-matrix reactivity that results in partially dissolved SiC particles and the formation of a TiC and Si5Ti3 ring around them. The size and number of particles and reaction products depend on the initial size and percentage of reinforcement and the DLD scanning speed. The higher the size and percentage of SiC particles and reaction products in the matrix, the higher the hardening effect of the composite matrix. Graphic
PubDate: 2022-05-18

• Exploring the Heat Treatment Parameters, Microstructural Evolution, and
Mechanical Properties of Ti–6Al–4V Alloy Fabricated by a Selective
Laser Melting Process

Abstract: The effects of heat treatment parameters on the mechanical properties of a selective laser melting Ti–6Al–4V alloy were studied using an L9 (34) type orthogonal test. Results showed that the solution temperature and aging temperature were the most influential factors relative to the mechanical properties. The optimum heat treatment was then obtained as 920 °C/2 h/water quenching + 550 °C/3 h/air cooling and the corresponding tensile strength was 1045.2 MPa and the elongation was 13.6%. Compared to a solution temperature of 850 °C, more fine secondary α phase (αS) and higher geometrically necessary dislocations (GND) density were obtained when solution temperature was 920 °C, which promoted the increased strength by increasing the interface strengthening effect of αS/β and the dislocation strengthening. However, the microstructure of the continuously coarsening αGB resulted in decreased elongation when the solution was at 920 °C. As the aging temperature increased from 550 to 650 °C, the GND density was reduced and the microstructures of primary α (αP), αS with various crystallographic orientations, lamellar α, and equiaxial αP were coarsened. Therefore, the elongation of the specimen aging at a higher aging temperature increased while the strength decreased. Graphical
PubDate: 2022-05-18

• Experimental Investigation and Modeling of Creep Curve of Zr–2.5Nb Alloy
by Machine Learning Techniques

Abstract: In the present work, creep tests on Zr–2.5Nb alloy at different stresses and temperatures in the two-phase region were carried out. The three creep regions were very distinct at low stresses and temperatures, whereas the secondary creep regions narrowed down considerably at higher temperatures and stresses. Data obtained from these creep tests were used to simulate the creep curves by multiple linear regression (MLR) and artificial neural network (ANN) modeling. The MLR model was able to predict the primary creep region accurately; however, it over-predicted the secondary creep region. ANN model could simulate all the three creep regions with very high accuracy, where 98% of the creep strain could be predicted within a deviation of ± 5%. Two different creep experiments were conducted to verify the predictability of the proposed models. The results indicate that the ANN technique can be used to predict the creep curves of two-phase alloys. Graphical
PubDate: 2022-05-18

• Evaluation of Microstructure, Residual Stress, and Mechanical Properties
in Different Planes of Wire + Arc Additive Manufactured Nickel-Based
Superalloy

Abstract: The present study investigates microstructure, mechanical characteristics, and residual stresses of alloy C-276 thick wall component manufactured by wire arc additive manufacturing technique. The microstructure of the fabricated thick wall part has been analysed in various regions. The microstructure at the top, intermediate, and bottom regions result in equiaxed, cellular, and columnar dendrites. Microsegregation was evaluated in the interdendritic regions of the top, intermediate, and bottom surfaces and in travel and build directions. Further in electron backscatter diffraction investigates the texture and microstructure of materials by utilising the inverse pole figure and grain boundary maps in travel and build directions. Also, as compared to low angle grain boundaries, the fraction of high angle grain boundaries is higher in build direction than travel direction. Further, residual stress analysis exhibits the tensile residual stress in the travel direction compared to build direction and compressive stresses were induced in the top region of the deposited part in the build direction. Also, no substantial deviations of microhardness values were in multiple as-deposited regions. Typically, the tensile properties of the material vary significantly across various direction such as horizontal, vertical and inclined. The higher tensile strength observed in the horizontal direction (745 ± 6.2 MPa) compared to vertical and inclined directions. This study provides better insights into the additively manufactured nickel-based superalloy's microstructure, residual stress and mechanical properties. Graphical
PubDate: 2022-05-17

• A New Digital Image Correlation Method for Measuring Wide Strain Range
True Stress–Strain Curve of Clad Materials

Abstract: Accurate evaluation of the nonlinear hardening behavior (i.e., wide strain range true stress–strain curve) of developed materials as structural materials is essential because it is directly related to user safety and is input data of simulation for plasticity, structural analysis, and sheet forming. However, the conventional methods to measure intrinsic mechanical properties can only characterize homogeneous materials, and the technique to evaluate heterostructured materials such as clad materials is lacking so far. In this study, the nonlinear hardening behavior of the clad material was evaluated using the tensile test and digital image correlation (DIC) to introduce the clad materials into the practical industry. The new method considers the mechanical properties of all layers constituting the clad material by observing the side surface of the specimen, unlike the conventional DIC methods of obtaining the true stress–strain curves from the images of the front surface of the specimen. The reliability of the obtained wide strain range true stress–strain curve calculated using the proposed method was validated using the finite element method simulation. The proposed method can provide trustworthy intrinsic mechanical properties of newly developed clad materials, which are promising next-generation materials. Graphical
PubDate: 2022-05-16

• Effect of Mechanical Alloying and Sintering Behavior on the Microstructure
and Properties of NbMoTaWRe Refractory High Entropy Alloy

Abstract: An equiatomic refractory high-entropy alloy (RHEA) NbMoTaWRe is prepared by mechanical alloying (MA) and spark plasma sintering (SPS). The effects of mechanical alloying and sintering behaviors on the microstructure and properties of the RHEA are investigated. After ball-milling for 30 h, the metastable and supersaturated MA powders with the body-centered cubic (BCC) structure are obtained. Then, the MA powders are sintered using the SPS method under the sintering temperature range of 1700–1900 °C, and the C atoms and WC introduced by the MA process reacts with the metastable and supersaturated Ta/Nb phase of the MA powers to form the face-centered cubic (FCC) structure (Nb, Ta)C particles along the BCC matrix boundaries during the SPS process. The NbMoTaWRe alloy sintered at 1800 °C consisted of BCC matrix and FCC-type (Nb, Ta)C particles has high compactness (porosity fraction is 0.32%), fracture strength (2630 MPa), plastic strain (6.82%), and hardness (992 ± 20 HV). These excellent properties of this RHEA are mainly attributed to the combination of multi-effects, including sintering densification, grain refinement strengthening from the refined sizes (3.80 μm) BCC matrix, precipitation strengthening from the (Nb, Ta)C particles, solid solution strengthening from multi-principal elements and interstitial solid solution strengthening from C atoms dissolving into BCC matrix. Graphical
PubDate: 2022-05-16

• Influence of Hydrogen Absorption on Stacking Fault of Energy of a
Face-Centered Cubic High Entropy Alloy

Abstract: Hydrogen-induced variation of stacking fault energy (SFE) of a CrMnFeCoNi high-entropy alloy (HEA) was quantitatively evaluated by transmission electron microscopy (TEM) using weak-beam dark-field (WBDF) technique. Width of Shockley partial dislocations turned out to increase after hydrogen absorption, which indicates that hydrogen decreases the SFE of the alloy: from 31.5 ± 3.5 to 22.5 ± 2.5 mJm−2 by introduction of hydrogen into the lattice with approximate concentration of 115 wppm. This report provides the first direct observation of stacking faults under the influence of hydrogen in a face-centered cubic metallic structure. Graphical
PubDate: 2022-05-16

• Importance of Microstructural Features in Bimodal Structure–Property

Abstract: The bimodal structure, one of the various heterogeneous microstructures, has been studied in an attempt to induce desirable strength-ductility synergies. We developed a physical-based constitutive model which represents the deformation mechanism well considering the evolution of geometrically necessary dislocations and statistically stored dislocation densities. Even though there are many complex correlations of grain size, volume fraction, and spatial distribution of coarse grain/fine grain in a bimodal structure, the bimodal structure-property linkage can be explored by adopting microstructure-based finite element method simulations. This work demonstrates that the bimodal microstructure-property linkage can be analyzed quantitatively to facilitate finding optimal heterogeneous equiaxed bimodal structures. Graphical
PubDate: 2022-05-15

• Evolution of Phases and their Influence on Shape Memory Effect by Varying
Sintering Parameters of NiTi Alloys

Abstract: NITINOL is the most popular and economic shape memory alloy (SMA) used in various industries. For temperature associated applications, the shape memory effect (SME) is the major phenomenon for the shape and strain recovery of materials after deformation. The machinability and cold working ability of NiTi alloys are poor compared to conventional alloys. So to reduce the post-processing of the finished product with good homogenization of elements, the powder technology route is suitable for making these SMAs. Due to the simplicity and cost-effectiveness, the uniaxial press and sinter process was used for pellet making. In this paper, before sintering 450, 475, 500, 525, 550, 575 and 600 MPa compaction pressures were analysed by their green densities and 600 MPa compacted pellet yielded the better density. Sintering was done at 950, 1000, 1050, 1100 and 1150 °C with the variation of sintering time 0.5, 1, 1.5 and 2 h. The XRD and SEM studies showed that samples sintered at 950 °C have oxide phases with elemental Ni and Ni3Ti phases. For samples sintered at 1000, 1050 and 1100 °C, NiTi and Ti2Ni formed as major phases with minor phases of βTi and Ni4Ti3 precipitates formed inside the NiTi matrix. It was difficult to detect the minor phases for the sample sintered at 1150 °C. Needle shaped martensitic NiTi forms inside the austenitic NiTi matrix and was detected at a very high magnification of 5000× in SEM. From the Differential Scanning Calorimetry study, it was found that an increase in sintering time and sintering temperature results in a faster shape memory response. Graphical
PubDate: 2022-05-14

• Successful Consolidation of Inoculant Alloy by Controlling Brazil Nut
Effect and Capillary Force

Abstract: Novel inoculant alloy (IA) for dispersion of inoculants in molten metal was developed. By mixing powders of inoculant and matrix, 3 combinations of IAs having different inoculants (TiN, Ce2O3) and size of matrix powder (coarse, fine) were produced and added into molten metal the confirm dispersion and refining effect. Also, how these 2 variables can affect to dispersion was investigated. The combination of TiN + coarse matrix powder (T–C) does not melt and failed to disperse because of continuously-networked structure of TiN originated from larger size of matrix powder than the inoculant. The combination of Ce2O3 + fine matrix powder (C–F) made of powders of similar size melted, however, failed because Ce2O3 agglomerated because of capillary force varying with inoculant species. Comparing capillary forces for different inoculants shows that Ce2O3 has stronger agglomeration tendency than TiN. The combination of TiN + fine matrix powder (T–F) made of TiN having weaker agglomeration tendency and fine matrix powder disperse inoculants and refine solidification structure. Graphical
PubDate: 2022-05-14

• Effect of Cooling Rate on Magnetic Properties of Fe-3.3 wt% Si
Non-oriented Electrical Steel

Abstract: In this paper, the effects of solidification cooling rate on the inclusion distribution, magnetic properties, and texture of 3.3 wt% Si non-oriented steel with different carbon and sulfur (C&S) levels are measured and analyzed. Fast and slow cooled strip samples produced using specially designed melt samplers were thermo-mechanically treated by hot rolling (HR), cold rolling (CR), and final annealing. The fully processed fast cooled sample (~ 1700 K/s) exhibited a smaller average grain size compared to the sample produced with a low solidification cooling rate (~ 9 K/s). In addition, under each C&S level, smaller inclusions (in the range 0.15–1.0 μm) were observed in the high solidification cooling rate sample. Differences in Cube {100}〈001〉, S{213}〈364〉, Brass{110}〈112〉, Goss{110}〈001〉, and Copper{112}〈111〉 texture were also documented in the fully processed material. Under each C&S level, the sample with low solidification cooling rate had a lower core loss than the high cooling rate sample. Graphical
PubDate: 2022-05-14

• Orientation Dependent Twinning Behavior in a Twinning-induced Plasticity
Steel Investigated by Nanoindentation

Abstract: The present work focuses on the mechanical behavior of single austenite grain with different orientations in a twinning induced plasticity (TWIP) steel by nanoindentation test. Deformation twins can be found in [0 0 1]-orientated grains after nanoindentation, while they are absent in grains with [1 1 1] orientation. This inconformity can be ascribed to a larger Schmid factor for leading partial dislocations compared to trailing partial dislocations on the primary slip system in [0 0 1]-orientated grains during compression. Different from deformation twins, high-density dislocations can be found in both [0 0 1] and [1 1 1]-orientated grains after nanoindentation. The present work suggests that the density of deformation twins can be enhanced by controlling crystal orientation through texture engineering or by deformation along different directions such as cross-rolling. Graphical abstract
PubDate: 2022-05-14

• Novel Strategy for Reducing Residual Stress in Titanium Alloy Parts

Abstract: The additive manufacturing of titanium alloy parts has important scientific significance and practical value. Controlling the distribution of residual stress caused by the high cooling rate and temperature gradient is the key to regulating the performance of devices obtained from additive manufacturing. In this work, the effects of the interlayer scanning angle on the residual stress in Ti–6Al–4V parts manufactured by selective laser melting were investigated by finite element simulations. We studied how changing the interlayer deflection angle alleviated residual stress under different energy inputs. The results showed that the residual stress in the z-direction was reduced by the deflection angle of 67° and 90°, and the non-uniform distribution of residual stress was reduced by a deflection angle of 67°. The combination of a chessboard pattern and interlayer deflection angle greatly alleviated the generation of residual stress. This work has important guiding significance for the additive manufacturing design of high-quality and high-performance titanium alloy devices. Graphical
PubDate: 2022-05-13

• Assessing the Residual Stresses in Dissimilar Welded Joint: Depth-Sensing
Indentation Testing and Numerical Simulation

Abstract: In this study, both the depth-sensing indentation (DSI) measurements and finite element (FE) simulations were performed to investigate the residual stress distribution in the Super304H/T92 dissimilar welded joint with Ni-based filler metal. To measure the residual stresses using the DSI technique, the stress-relieving annealing method was adapted for the welded joint to obtain the in-situ reference curves corresponding to the as-welded state. The distribution of the residual stress across the welded joint was then obtained using Suresh-Atar model combined with the DSI measured results, and the results were in good agreement with the measured results by XRD. Besides, pile-up and sink-in phenomena were observed in the residual indentation morphologies. It is found that the dispersion of local residual stresses was related to the heterogeneous microstructures. To further understand the formation causes of the measured residual stress distribution, a thermal-metallurgical-mechanical finite element analysis was also performed in this study. It was suggested that the combined effects of structural size and material properties may be responsible for the measured residual stress distribution. The research work of this paper would further extend the applications of the DSI technique in the welding residual stress testing field. Graphical abstract
PubDate: 2022-05-13

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