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  • Simultaneous improvement in strength and plasticity of Ti-24Nb-4Zr-8Sn manufactured by selective laser melting
    Mater. Des. (IF 4.525) Pub Date : 2018-07-17
    C.L. Yang, Z.J. Zhang, S.J. Li, Y.J. Liu, T.B. Sercombe, W.T. Hou, P. Zhang, Y.K. Zhu, Y.L. Hao, Z.F. Zhang, R. Yang

    The strength and plasticity of metallic materials usually exhibit a trade-off relation. This study reports a simultaneous improvement in the ultimate tensile strength (UTS) and uniform elongation (UE) of Ti-24Nb-4Zr-8Sn (Ti2448) fabricated by selective laser melting (SLM), relative to those produced via forging. Detailed microstructural characterization reveals that the outstanding tensile property may result from the bi-model structure that forms during the rapid cooling associated with SLM. Coarse grains are surrounded by fine grains within the melt pool, which causes a back stress during tension. The back stress provides additional strain-hardening capacity, which postpones the initiation of necking and then leads to the simultaneous improvement of the strength and plasticity (SISP) of the Ti2448 alloy. Furthermore, the tensile property of the SLM-fabricated sample is anisotropic which is strongly related to the irregular shape of the melt pool.

    更新日期:2018-07-18
  • HITEMAL-an outer sheath material for MgB2 superconductor wires: The effect of annealing at 595–655 °C on the microstructure and properties
    Mater. Des. (IF 4.525) Pub Date : 2018-07-17
    Martin Balog, Alica Rosova, Bronislava Szundiova, Lubomir Orovcik, Peter Krizik, Peter Svec, Miloslav Kulich, Lubomir Kopera, Pavol Kovac, Imrich Husek, Ahmed Mohamed Hassan Ibrahim

    An aluminum material stabilized with a 1.6 vol% of nanometric Al2O3 dispersoids, named HITEMAL, was fabricated by hot extrusion of a fine atomized Al powder. The Al2O3 dispersoids stemmed from a native Al2O3 films on an aluminum powder surface. An extruded rod of the material was then cold-deformed out into a thin wire by rotatory swaging, hydro extrusion and rolling. Such severely deformed HITEMAL was studied as a prospective outer sheath stabilizer material for MgB2 core superconductor wires. An emphasis was put on the effect of annealing realized at various temperatures close to the melting point of Al, which is typically applied to form an in-situ MgB2 superconductive core, on the mechanical and electrical properties of the HITEMAL wire. A systematic investigation was performed of changes to a severely deformed Al grain structure and Al2O3 dispersoids upon annealing the as-deformed wire from 595 to 655 °C for 30 min. Mechanical and electrical properties of the wire were measured at room and cryogenic temperatures. The results showed that the ultrafine-grained Al + 1.6 vol% Al2O3 wire exhibited advantageous properties, and surface integrity after annealing up to 642 °C. It is thus a lightweight material of choice for outer sheaths of MgB2 superconductors.

    更新日期:2018-07-18
  • Inelastic deformation micromechanism and modified fragmentation model for silicon carbide under dynamic compression
    Mater. Des. (IF 4.525) Pub Date : 2018-07-17
    Zhiyong Wang, Peifeng Li, Weidong Song

    The underlying micromechanism remains to be clarified for the bulk inelastic behaviour of specific ceramics under impact loads. In this study, the silicon carbide materials were subjected to the split-Hopkinson pressure bar compression in which the strain rate was not constant but increased to the dynamic level at high stresses. The inelastic deformation occurs in the high strain rate stage in compression, followed by the final transgranular fracture. The post-test fragments were examined in both the SEM and high resolution TEM. It was found that macroscopic inelastic behaviour is dominated by the dislocation motion and the localised amorphisation that arise at high strain rates. The damage and thus the degraded modulus in the dynamic inelastic deformation were incorporated to modify a dynamic fragmentation model to evaluate the fragment size as a function of strain rates. The modified model more accurately predicts the size of fragments produced at high strain rates.

    更新日期:2018-07-18
  • Coherent diffraction study of calcite crystallization during the hydration of tricalcium silicate
    Mater. Des. (IF 4.525) Pub Date : 2018-07-17
    Xianping Liu, Wei Lin, Bo Chen, Fucai Zhang, Piqi Zhao, Aaron Parsons, Christoph Rau, Ian Robinson

    The aim of this work is using Bragg coherent X-ray diffraction imaging (BCDI) to study the calcite crystallization during carbonation of hydrated tricalcium silicate (C3S). Portland cement is a very complex synthesized product whose 50–70% mass is composed of C3S, which is the most important phase to produce calcium silicate hydrates and calcium hydroxide. Hence, its hydration contributes greatly to the hydration of cement and later to the carbonation of cement products when it reacts with CO2, often from the air, to form calcium carbonates. BCDI has emerged in the last decade as a promising high-resolution lens-less imaging approach for characterization of various samples. It has made significant progress with the development of X-ray sources and phase-retrieval algorithms. BCDI allows for imaging the whole three-dimensional structure of micro- and sub-micro- crystalline materials and can show the strain distribution at the nanometer spatial resolution. Results show that calcite crystallization follows a through-solution reaction and the growth model of the calcite crystal can be explained by using “phase domain” theory. During carbonation, calcite crystals grow by increasing the number of phase domains within them while the domain size remains at about 200–300 nm.

    更新日期:2018-07-18
  • Highly sensitive 4H-SiC pressure sensor at cryogenic and elevated temperatures
    Mater. Des. (IF 4.525) Pub Date : 2018-07-10
    Tuan-Khoa Nguyen, Hoang-Phuong Phan, Toan Dinh, Karen M. Dowling, Abu Riduan Md Foisal, Debbie G. Senesky, Nam-Trung Nguyen, Dzung Viet Dao

    The slow etching rate of conventional micro-machining processes is hindering the use of bulk silicon carbide materials in pressure sensing. This paper presents a 4H-SiC piezoresistive pressure sensor utilising a laser scribing approach for fast prototyping a bulk SiC pressure sensor. The sensor is able to operate at a temperature range from cryogenic to elevated temperatures with an excellent linearity and repeatability with a pressure of up to 270 kPa. The good optical transparency of SiC material allows the direct alignment between the pre-fabricated piezoresistors and the scribing process to form a diaphragm from the back side. The sensitivities of the sensor were obtained as 10.83 mV/V/bar at 198 K and 6.72 mV/V/bar at 473 K, which are at least a two-fold increment in comparison with other SiC pressure sensors. The high sensitivity and good reliability at either cryogenic and elevated temperatures are attributed to the profound piezoresistive effect in p-type 4H-SiC and the robust p-n junction which prevents the current from leaking to the substrate. This indicates the potential of utilising the laser scribing approach to fabricate highly sensitive bulk-SiC pressure sensors for harsh environment applications.

    更新日期:2018-07-12
  • Determination of the hyper-viscoelastic model parameters of open-cell polymer foams and rubber-like materials with high accuracy
    Mater. Des. (IF 4.525) Pub Date : 2018-07-10
    Balint Fazekas, Tibor J. Goda

    This paper focuses on a newly-developed method for the extraction of the accurate hyper-viscoelastic model parameters of open-cell polymer foams and rubber-like materials. Although the parameter identification method is developed for strain-controlled uniaxial tension/compression, the finite time increment-based approach used can be extended to other experimental loading modes, such as simple and pure shear, biaxial tension/compression, confined compression, etc. Furthermore, the method makes it possible to use any hyperelastic material model and to extract the constitutive model parameters of both compressible and incompressible hyper-viscoelastic solids subjected to arbitrary strain (stretch) history. The applicability of the method and the reliability of the constitutive model parameters determined from the numerical prediction of the stress response are proved through the comparison of finite element and measurement results. Finally, the material model parameters of an incompressible isoprene rubber and a compressible polyurethane foam extracted with the proposed method and those determined with the two-step and the direct (closed-form) method are used to compare the accuracy of the predicted behaviours. It clearly revealed that the constitutive constants extracted using the proposed direct (numerical) method result in the best agreement between the measurement and the simulation.

    更新日期:2018-07-12
  • Improving the Mode-II Interlaminar Fracture Toughness of Polymeric Matrix Composites through Additive Manufacturing
    Mater. Des. (IF 4.525) Pub Date : 2018-07-10
    V. Damodaran, A.G. Castellanos, M. Milostan, P. Prabhakar

    Delamination is a common failure mode observed in fiber reinforced polymeric composites subjected to thermo-mechanical loads. Reinforcements at the interlaminar regions or in the through-thickness direction have been previously shown to improve the damage resistance and durability of these composites. In particular additive manufacturing (AM), also called 3D printing, has been shown to increase the interlaminar shear strength when used for custom printing of polymer reinforcements over carbon fiber prepreg prior to the layup process of layered composites. In this paper, printing of interlaminar polymer reinforcements using fused deposition modeling (FDM) technique within AM is proposed for improving the interlaminar fracture toughness of carbon fiber laminates. The rationale behind this improvement in the interlaminar fracture toughness values due to printed polymer reinforcements (PPR) is investigated by elucidating the influence of varying the process parameters, such as print speed, spacing, and dimensions. An in-depth understanding of the bond quality between the prepregs and the printed polymers as well as the interlaminar fracture surfaces formed on the Mode-II fracture toughness values are established by developing an experimentally validated thermo-chemical finite element modeling framework.

    更新日期:2018-07-12
  • Optimizing the performance of the bulk heterojunction organic solar cells based on DFT simulations of their interfacial properties
    Mater. Des. (IF 4.525) Pub Date : 2018-07-10
    Sarah A. Ayoub, Jolanta B. Lagowski

    Experimental studies suggest that the intermolecular interactions between polymers and fullerenes are critical to the design of efficient bulk heterojunction organic photovoltaic cells. However, a detailed understanding of these intermolecular interactions is still lacking. In this work, by correlating simulation data with experimentally determined efficiencies, we identify interfacial factors that can be used to enhance the performance of BHJ organic solar cells (OSCs). We employ dispersion corrected density functional theory method (B97D3) to investigate the properties of the interfacial region in various promising combinations of monomers (P3HT, PTB7, PCDTBT, PBDTTPD, PNT4T, PffBT4T, and PBTff4T) and fullerenes (PCBM and PC71BM) used in OSCs. We analyze the conformational structures and binding energies of these combinations, and obtain the electronic offsets of gas phase and interacting monomers and fullerenes. Our findings indicate that monomer/fullerene pairs that exhibit the highest experimentally determined PCEs (i.e. those containing PNT4T, Pff4TBT, and PBTff4T) have the following common characteristics: the lowest interfacial LUMO offset, the largest ratio of Voc (as determined by interfacial band gap) to monomer's energy gap, Eg, and a relatively high binding energy. We believe that selecting materials with these interfacial properties will lead to a development of OSCs with higher efficiencies.

    更新日期:2018-07-12
  • Compressive properties of hollow lattice truss reinforced honeycombs (Honeytubes) by additive manufacturing: Patterning and tube alignment effects
    Mater. Des. (IF 4.525) Pub Date : 2018-07-11
    Jun Xu, Yaobo Wu, Lubing Wang, Jiani Li, Yuwei Yang, Yuli Tian, Zizheng Gong, Pinliang Zhang, Steven Nutt, Sha Yin

    Honeytubes, a novel type of honeycomb formed by reinforcement with lattice trusses, were reported to exhibit enhanced buckling resistance. However, an in-depth analysis for the compressive performance and energy absorption capacity was lacking. In this paper, the effects of microstructure and tube alignment on compressive properties were studied. Four types of honeytubes were designed based on different topologies, geometries and tube patterns, and fabricated by selective laser sintering (SLS). Out-of-plane compression tests and finite element simulation were performed for the analysis. Results indicated that incorporation of lattice in honeycombs resulted in greater local strain in tubes and tube-rib connections. However, honeytubes exhibited superior energy absorption capability, even surpassing that of some metallic lattices. Balancing the configuration of tubes in honeytubes could ensure enhanced mechanical performance. This work demonstrates that materials designed by capitalizing on micro-topologies can regulate mechanical properties and provide insights for guiding the development of new materials.

    更新日期:2018-07-12
  • Crashworthiness multi-objective optimization of the thin-walled tubes under probabilistic 3D oblique load
    Mater. Des. (IF 4.525) Pub Date : 2018-07-11
    Mohammad Arjomandi Rad, Abolfazl Khalkhali

    In a real-world loading case (e.g., car crash accidents), energy-absorbing components are subject to oblique loads at various uncertain angles. This paper aims to investigate the behavior of such components under three-dimensional (3D) oblique loads in deterministic and probabilistic loading conditions. In this way, some square tubes are tested experimentally, and results are utilized to validate numerical models. To apply the 3D oblique load, a special test setup is designed, constructed, and installed on a universal tensile testing machine. Hammersley method is employed to design sample points. ABAQUS software is used for the finite element modeling and analysis. GEvoM software is implemented for mapping design variables onto crashworthiness characteristics including energy absorption (EA) and peak crush force (PCF). Both deterministic and reliability-based robust design (RBRD) optimizations are performed, and their results are compared with each other. The primary outcome of this research is the effect of incidence angles on the energy-absorbing characteristics, as well as some remarkable trade-off design points obtained from various multiple-criteria decision-making (MCDM) methods. It was discovered that the obtained design points of probabilistic study, which satisfied the reliability constraint, were roughly 60% more robust than deterministic points.

    更新日期:2018-07-12
  • Design of alumina monoliths by emulsion-gel casting: Understanding the monolith structure from a rheological approach
    Mater. Des. (IF 4.525) Pub Date : 2018-07-09
    Nayan Nayak, Nuno Vitorino, Jorge R. Frade, Andrei V. Kovalevsky, Vitor D. Alves, João G. Crespo, Carla A.M. Portugal

    Multimodal porous cellular alumina structures (monoliths) were prepared by an emulsion-gel casting technique using eco-friendly and inexpensive lipids such as corn oil, castor oil, margarine and their mixtures as the dispersed phase. The monoliths obtained showed a good mechanical stability, exhibiting compressive strengths in the range of 8–50 N·mm−2. Mercury intrusion porosimetry analysis showed that the monoliths produced presented porosities ranging from 28% to 60% and average pore sizes within 0.2–3.2 μm. The formation of the porous networks was interpreted based on combined droplet coalescence, flocculation and Ostwald ripening effects. The presence of such effects along the emulsion storage time led to changes in their viscoelastic and morphological properties, which were found to correlate with structural descriptors of monoliths after sintering (e.g. average pore sizes and porosity). These correlations open up the possibility to anticipate the final structure of the monoliths and adjust emulsion-gel conditions to produce customized cellular structures with fine-tuned porosities and pore sizes, envisaging their application in membrane processes or chromatography.

    更新日期:2018-07-10
  • 3D printing of materials with spatially non-linearly varying properties
    Mater. Des. (IF 4.525) Pub Date : 2018-07-09
    Luquan Ren, Zhengyi Song, Huili Liu, Qinghe Han, Che Zhao, Brian Derby, Qingping Liu, Lei Ren

    Functionally graded materials (FGMs) with spatially varying material properties in 3D space are highly desired for a wide range of applications. Although FGMs are ubiquitous in biological materials, the fabrication of FGMs with continuous non-linear spatial variation of material properties remains a great challenge. Here we present a self-developed extrusion-based additive manufacturing system capable of fabricating FGMs with sophisticated material property distributions. The workflow involves property function modeling, gray-scale representation and control codes generation, digital material feeding and active multi-material mixing. The effectiveness of the technology is demonstrated by the successful printing of a diverse range of objects with complex spatial variations in color and Al2O3 concentration. In addition, by controlling the dynamic change of the different components during reactive 3D printing process, we can fabricate polyurethane (PU) objects with various gradient patterns in material mechanical properties. The results of the cantilever bending test and simulation show that the material gradient can effectively relieve the stress concentration. The proposed gradient 3D printing system opens a new avenue for manufacturing FGMs with exquisite material property distributions thus far only accessible by biological materials grown in nature.

    更新日期:2018-07-10
  • Carbon nanotube reinforced HVOF sprayed WC-Co coating
    Mater. Des. (IF 4.525) Pub Date : 2018-07-05
    Deviprasanna Mohanty, Simanchal Kar, Soumitra Paul, P.P. Bandyopadhyay

    This investigation deals with the study of 1 wt% carbon nanotube (CNT) reinforced high velocity oxy-fuel sprayed conventional and nanostructured WC-Co coatings deposited on Ti-6Al-4V coupons. Coatings were also prepared from the as-received powders for comparison purpose. The reinforced coatings exhibited up to 30%, 10% and 33% increase in hardness, elastic modulus and cohesive strength, respectively. The graphene structure of the CNT was retained in the coating. The reinforced coatings demonstrated a significant reduction in specific wear rate during ball-on-disc tribometry. The forces and specific energy recorded during surface grinding of the reinforced coatings were substantially higher than those of the coatings produced from the as-received powders. The residual stress of the as-sprayed coatings was compressive in nature. The magnitude of this stress increased further on surface grinding.

    更新日期:2018-07-08
  • The printability, microstructure, crystallographic features and microhardness of selective laser melted Inconel 718 thin wall
    Mater. Des. (IF 4.525) Pub Date : 2018-07-05
    Huihui Yang, Jingjing Yang, Wenpu Huang, Zemin Wang, Xiaoyan Zeng

    The thin plate is a promising light-weight structure to broaden applications of Inconel 718 superalloy in aerospace and transportation industries. In the present work, selective laser melting (SLM) technology was applied to manufacture a series of Inconel 718 thin walls (ultra-thin plates) to explore their printability, microstructures, crystallographic features and microhardness under keyhole and conduction modes. Results show that it is feasible to manufacture Inconel 718 thin walls with a thickness of ~0.2 mm by SLM. Keyhole mode is favorable for a better printability, finer dendrites, the precipitation of strengthening phases of γ′/γ″, a stronger 〈001〉 texture intensity and a higher microhardness in the center zone of the SLMed thin wall. Conduction mode contributes to the uniform microstructures and microhardness in the marginal and center zones of the thin wall. Also, the decrease of area fraction in strengthening phases and the increase of Laves phase result in a decreasing trend of microhardness along the deposition direction. Finally, microstructural formation and evolution mechanisms of SLMed thin walls under two modes are proposed based on the solidification conditions and vertical thermal cycles.

    更新日期:2018-07-08
  • ANN prediction of corrosion behaviour of uncoated and biopolymers coated cp-Titanium substrates
    Mater. Des. (IF 4.525) Pub Date : 2018-07-06
    Suman Kumari, Hanuma Reddy Tiyyagura, Timothy E.L. Douglas, Elbeshary A.A. Mohammed, Annemie Adriaens, Regina Fuchs-Godec, M.K. Mohan, Andre Skiratch

    The present study focuses on biopolymer surface modification of cp-Titanium with Chitosan, Gelatin, and Sodium Alginate. The biopolymers were spin coated onto a cp-Titanium substrate and further subjected to Electrochemical Impedance Spectroscopic (EIS) characterization. Artificial Neural Network (ANN) was developed to predict the Open Circuit Potential (OCP) values and Nyquist plot for bare and biopolymer coated cp-Titanium substrate. The experimental data obtained was utilized for ANN training. Two input parameters, i.e., substrate condition (coated or uncoated) and time period were considered to predict the OCP values. Backpropagation Levenberg-Marquardt training algorithm was utilized in order to train ANN and to fit the model. For Nyquist plot, the network was trained to predict the imaginary impedance based on real impedance as a function of immersion periods using the Back Propagation Bayesian algorithm. The biopolymer coated cp-Titanium substrate shows the enhanced corrosion resistance compared to uncoated substrates. The ANN model exhibits excellent comparison with the experimental results in both the cases indicating that the developed model is very accurate and efficiently predicts the OCP values and Nyquist plot.

    更新日期:2018-07-08
  • Ultra-low shrinkage chitosan aerogels trussed with polyvinyl alcohol
    Mater. Des. (IF 4.525) Pub Date : 2018-07-06
    Sizhao Zhang, Junzong Feng, Jian Feng, Yonggang Jiang, Liangjun Li

    Naturally-derived materials have attracted numerous attention owing to a unique native set of properties, but the significant shrinkage of biomass aerogel, from its final wet gel to aerogel, remains a formidable challenge. Here we explore a strategy based on supramolecular interaction and covalent crosslinking to overcome the inherent large shrinkage of chitosan aerogel, by reinforcing its molecular-level structure. The introduction of linear polyvinyl alcohol (PVA) chains can adequately interpenetrate with crosslinked chitosan chains to form strong intermolecular network architecture. Chitosan aerogel trussed with PVA enables to be readily fine-tuned, simultaneously giving rise to nano-sized cellular voids inside the aerogel. Chitosan aerogel obtained shows good heat insulation, applicable compressive property and exceptional processing feature of special-shaped components. We also find an emergent phenomenon that the addition of PVA may steer desirable orientation shrinkage, and linear elasticity at low strain in terms of chitosan aerogel.

    更新日期:2018-07-08
  • Development of flexible particle-laden elastomeric textiles with improved penetration resistance to hypodermic needles
    Mater. Des. (IF 4.525) Pub Date : 2018-07-07
    Dariush Firouzi, Mohammed K. Russel, Syed N. Rizvi, Chan Y. Ching, Ponnambalam R. Selvaganapathy

    Needle stick injuries are a major concern for workers in hospitals, service and hospitality sectors. Current prevention strategies include double/triple gloving reduce flexibility significantly and also do not provide a significant reduction in injuries as desired. Here, we develop a new particle-laden elastomer using colloidal silica (CS) and polydimethylsiloxane (PDMS) which when coated onto high-density polyethylene (HDPE) woven fabric shows a remarkable 90% increase in specific penetration resistance force (SPRF) to hypodermic needles as compared to the neat fabric. We show that the resistance to penetration is dependent on the concentration of the hard silica particles and hypothesize that a percolation network of connected particles form upon impact that distributes the load and provides high resistance. We term this phenomenon as elastic jamming. Furthermore, we also show that by adding silicon carbide nanoparticles to CS increases the SPRF to 110% of neat fabric. A two-layer stack of the same treated fabric was able to completely prevent the penetration of a 21 G needle at a speed of 50 cm/min in about one-third of the performed experiments. These results demonstrate that impregnation of textiles with these nanocomposites can be an attractive method for the manufacture of needle stick penetration resistant garments.

    更新日期:2018-07-08
  • Biomimetic hydroxyapatite/gelatin composites for bone tissue regeneration: Fabrication, characterization, and osteogenic differentiation in vitro
    Mater. Des. (IF 4.525) Pub Date : 2018-07-07
    He Lian, Liping Zhang, Zhaoxu Meng

    Herein, we prepared a series of novel hydroxyapatite (HA) nanowire and gelatin composite films with varying HA to gelatin ratios, attempting to simulate the major features of the natural extracellular matrix of bone. The results showed that the ratio of HA nanowires to gelatin had a great influence on the physicochemical and biological properties of the composites. The morphology of the HA/gelatin 7/3 composite film had a fibrous and porous architecture, while the 5/5 and 3/7 samples led to the formation of non-porous rough surfaces. Additionally, an increase in HA content enhanced the composite mechanical properties, with a maximum tensile strength of 114 ± 8 MPa, respectively. The HA/gelatin composite films exhibited good cell adhesion and proliferation. Osteogenic differentiation of mouse bone marrow mesenchymal stem cells on the 7/3 composite film was superior to that of the remaining films, as evident by alkaline phosphatase activity, calcium deposition, and gene expression. Thus, the HA/gelatin 7/3 composite film prepared herein has potential as a bone substitute for bone repair and regeneration.

    更新日期:2018-07-08
  • Local chemical ordering within the incubation period as a trigger for nanocrystallization of a highly supercooled Ti-based liquid
    Mater. Des. (IF 4.525) Pub Date : 2018-07-07
    Zhi Wang, Chunlin Chen, Sergey V. Ketov, Kazuto Akagi, Andrey A. Tsarkov, Yuichi Ikuhara, Dmitri V. Louzguine-Luzgin

    In the present work we study nanocrystallization of the Ti50Ni23Cu22Sn5 alloy within the supercooled liquid region by using a state-of-the-art experimental technique with elemental mapping at near-atomic resolution especially focusing on the incubation period which is still poorly understood from both the theoretical and experimental viewpoint. Molecular dynamics (MD) simulation results performed for the Ti55Ni45 liquid acting as a simplified model system of the (Ti,Sn)55(Ni,Cu)45 alloy illustrate the process of nucleation and provide some additional suggestions. The experiment and MD results indicate formation of nanometer-range chemical rearrangements which are supposed to reduce the energy barrier in the complex energy landscape finally leading to a high density of homogeneously nucleating crystallites after the completion of a macroscopically observed incubation period.

    更新日期:2018-07-08
  • Effect of heat treatments on microstructural evolution of additively manufactured and wrought 17-4PH stainless steel
    Mater. Des. (IF 4.525) Pub Date : 2018-07-07
    Yu Sun, Rainer J. Hebert, Mark Aindow

    Additively manufactured (AM) components usually have nonequilibrium microstructures. Post-built heat treatments are recommended for AM components to achieve homogenous microstructures. In this study, the effects were investigated of conventional solutionizing and precipitation hardening (H-900) heat treatments on the microstructure evolution of 17-4PH AM and wrought components. Microstructural characterization techniques including SEM, TEM and EBSD analysis were used on 17-4PH AM and wrought components to obtain quantitative information about the microstructure and phase evolution during these heat treatments. These microstructural studies demonstrate that 17-4PH AM components can achieve microstructures and hardnesses similar to those of wrought samples by post-built heat treatments.

    更新日期:2018-07-08
  • Interlayer adhesion and fracture resistance of polymers printed through melt extrusion additive manufacturing process
    Mater. Des. (IF 4.525) Pub Date : 2018-07-04
    Nahal Aliheidari, Josef Christ, Rajasekhar Tripuraneni, Siva Nadimpalli, Amir Ameli

    This study aims to establish the relationships between the process parameters, mesostructural features (interlayer neck and void sizes), and the fracture resistance of 3D printed parts. The proposed method enables the decoupling of bond quality and mesostructure effects on the overall fracture behavior. Double cantilever beam specimens of acrylonitrile butadiene styrene (ABS) were designed, printed, and fracture tested. The apparent fracture resistance (Jc,a), the interlayer fracture resistance (Jc,i), and the microstructure were characterized. The fracture results and the microscopic examinations indicate that Jc,a is strongly correlated with the process parameters through both the interlayer adhesion as well as the mesostructure. Nozzle and bed temperatures and layer height were found to have significant effects on the fracture behavior. For instance, the Jc,a increased by 38% with a 20 °C increase in the nozzle temperature. This originated from 15% increase in the interlayer fracture resistance and 23% increase in the actual fracture surface area (interlayer neck size). The quality of interlayer bond was explained in terms of temperature, pressure, and time of the process. This work quantifies the relationships between the printing process and the fracture behavior and provides novel tools and insights in the design and analysis of printed materials.

    更新日期:2018-07-05
  • Development of novel Cu-Cr-Nb-Zr alloys with the aid of computational thermodynamics
    Mater. Des. (IF 4.525) Pub Date : 2018-07-04
    Ying Yang, Ling Wang, Lance Snead, Steven J. Zinkle

    Multi-modal precipitate distribution in the microstructure, with coarse precipitates pinning the grain boundaries and finer precipitates strengthening the matrix, is beneficial to suppress grain boundary sliding and dislocation creep, respectively, of structural materials. However, achievement of a multi-modal precipitate distribution remains a challenge in developing creep-resistant advanced Cu alloys while retaining high strength and high conductivity at elevated temperature. This work overcame this challenge with the aid of computational thermodynamics. Thermodynamic models for Gibbs energy functions of phases in the Cu-Cr-Nb-Zr system have been developed in this study. These models were then used to calculate solidification paths and phase equilibria at different temperatures, guiding the design of chemical composition and heat treatment parameters of novel copper alloys with a target multi-modal distribution of precipitates. The new alloy, fabricated through traditional ingot metallurgy method, has achieved the desired microstructure as validated by optical and transmission electron microscopy. Electrical conductivity and mechanical properties were screened and compared with the existing commercial Cu alloys.

    更新日期:2018-07-05
  • Extraction and evaluation of melt pool, plume and spatter information for powder-bed fusion AM process monitoring
    Mater. Des. (IF 4.525) Pub Date : 2018-07-03
    Yingjie Zhang, Geok Soon Hong, Dongsen Ye, Kunpeng Zhu, Jerry Y.H. Fuh

    With the continuous development of additive manufacturing technique, the issue on built quality has caught increasing attentions. To improve the quality of built parts, the process monitoring and control has been emphasized as a promising solution. Despite a large number of studies on the development of sensors and instrumentations, the investigation on statistical analysis, modelling and automatic anomalies detection is still at an infant stage. To advance the related research, the intelligent classification methods, support vector machines (SVM) and convolutional neural network (CNN), were proposed for quality level identification in this work. A vision system with high speed camera was used for process images acquisition. The features of different objects including melt pool, plume and spatter were extracted based on the AM process understanding. The corresponding feature vectors were used as the input for the SVM classification. The results indicated the information from different objects is sensitive to different types of quality anomalies. Moreover, the combination of features from these three objects can significantly improve the classification accuracy to 90.1%. Additionally, the comparison between SVM and CNN was also conducted, the high accuracy of 92.7% for the CNN model demonstrated that it is a promising method for quality level identification by using the vision system.

    更新日期:2018-07-04
  • Inconel 625 lattice structures manufactured by selective laser melting (SLM): Mechanical properties, deformation and failure modes
    Mater. Des. (IF 4.525) Pub Date : 2018-07-03
    Martin Leary, Maciej Mazur, Hugh Williams, Eric Yang, Ahmad Alghamdi, Bill Lozanovski, Xuezhe Zhang, Darpan Shidid, Lena Farahbod-Sternahl, Gerd Witt, Ingomar Kelbassa, Peter Choong, Ma Qian, Milan Brandt

    Additive Manufacture enables the fabrication of highly complex lattice structures with exceptional engineering properties. Inconel is a technically useful material in that it provides high resistance to oxidisation, creep and loss of mechanical properties at elevated temperatures. The combination of Inconel material properties and the geometric freedom of AM provides a unique opportunity for the fabrication of engineered structures with exceptional strength and stiffness at elevated temperatures, as for example is required for high temperature turbomachinery. Despite the associated technical opportunities, there exists no design data on the mechanical response, deformation characteristics and failure modes of AM Inconel 625 lattice structures. This research provides a comprehensive reference for the mechanical response of Inconel 625 lattice structures fabricated by Selective Laser Melting (SLM). Furthermore, the high ductility of inconel 625 lattice enables novel insight into the structural mechanics of AM lattice, and the associated deformation photography provides a reference for the validation and verification of numerical models of AM lattice behaviour.

    更新日期:2018-07-04
  • Mechanism of porosity formation and influence on mechanical properties in selective laser melting of Ti-6Al-4V parts
    Mater. Des. (IF 4.525) Pub Date : 2018-07-03
    Jonathan Stef, Angéline Poulon-Quintin, Abdelkrim Redjaimia, Jaafar Ghanbaja, Olivier Ferry, Matthias De Sousa, Mohamed Gouné

    An original approach based on 2D fracture surface and 3D X-ray tomography analysis is proposed in this paper. Its application in selective laser melting of Ti-6Al-4V provides substantive clarifications regarding both mechanisms of porosity formation and their influence on mechanical properties. Unambiguously, a one-to-one relationship between the scanning strategy pattern and the 3D spatial distribution of porosities is highlighted. In an original manner, the 3D location of porosities, their morphology and their orientation are analyzed with respect to the laser spot path. The results show that pores are mainly localized on the overlay zones and support the lack of energy induced by the lower energy at the periphery of the laser spot as the main mechanism of porosity formation. Finally, both tensile properties and crack path are shown to be influenced by the presence and 3D distribution of porosities.

    更新日期:2018-07-04
  • Processing, structure and thermal conductivity correlation in carbon fibre reinforced aluminium metal matrix composites
    Mater. Des. (IF 4.525) Pub Date : 2018-07-03
    Alberto Torres Miranda, Leandro Bolzoni, Nilam Barekar, Yan Huang, Jesik Shin, Se-Hyun Ko, Brian John McKay

    Al matrix composites reinforced with Cu-coated pitch-based carbon fibres (Al/Cu-CFs) were fabricated, using a novel combination of rheocasting and equal channel angular extrusion (ECAE) techniques, in order to exploit the thermal conductivity (K) of the material. Rheocasting allowed the introduction and dispersion of Cu-CFs within the Al3Mg matrix. The subsequent ECAE processing reduced the porosity of the composites from 3 to 0.03% and induced a high degree of fibre alignment within the matrix, although considerable damage to the fibres occurred during this processing step. After 6 ECAE passes, in which the billet orientation remained constant, the composite with the highest degree of fibre alignment show a thermal conductivity (K) improvement of ~20% with respect to the rheocast composite. The improvement is due to porosity reduction, improved fibre alignment and forced intimate contact of clean CF surfaces with the matrix.

    更新日期:2018-07-04
  • Light-based additive manufacturing of PolyHIPEs: Controlling the surface porosity for 3D cell culture applications
    Mater. Des. (IF 4.525) Pub Date : 2018-07-04
    Colin Sherborne, Robert Owen, Gwendolen C. Reilly, Frederik Claeyssens

    Using stereolithography (vat photopolymerisation) to polymerise High Internal Phase Emulsions (PolyHIPEs) is a potent additive manufacturing route to produce materials with a hierarchical porosity. These multiscale porous materials have a microporosity (1–50 μm) dictated by emulsion templating and a macroporosity (100 μm upwards) controlled by additive manufacturing. The interconnected, hierarchical porosity of these structures is particularly desirable in the field of bone tissue engineering as it promotes tissue formation and allows efficient mass transport. However, due to the high light-scattering nature of the HIPEs, the achievable feature resolution is poor in comparison to other photocurable polymers, and they are prone to the formation of a closed porosity ‘skin layer’ at the surface. This study focuses on different methods of both improving the resolution of structures fabricated from HIPEs via stereolithography and minimising skin formation. The inclusion of 2-(2H-Benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (commercially UV-234 or Tinuvin®234), a UV light-absorber, was found to significantly improve the achievable resolution of PolyHIPE structures fabricated via stereolithography with no cytotoxic effects and reduce the skin formation. Furthermore, in direct comparison with a non-microporous scaffold of the same architecture, the inclusion of a microporosity significantly promoted the proliferation of MLO-A5 murine osteoblasts and permitted superior bone-matrix deposition.

    更新日期:2018-07-04
  • Thermo-mechanical post-treatment: A strategic approach to improve microstructure and mechanical properties of cold spray additively manufactured composites
    Mater. Des. (IF 4.525) Pub Date : 2018-07-02
    N.H. Tariq, L. Gyansah, X. Qiu, H. Du, J.Q. Wang, B. Feng, D.S. Yan, T.Y. Xiong
    更新日期:2018-07-02
  • Fabrication of robust and scalable superhydrophobic surfaces and investigation of their anti-icing properties
    Mater. Des. (IF 4.525) Pub Date : 2018-07-02
    Nan Wang, Lingling Tang, Wei Tong, Dangsheng Xiong
    更新日期:2018-07-02
  • Temperature dependence of strain rate sensitivity, indentation size effects and pile-up in polycrystalline tungsten from 25 to 950 °C
    Mater. Des. (IF 4.525) Pub Date : 2018-07-02
    Ben D. Beake, Adrian J. Harris, Jonathan Moghal, David E.J. Armstrong
    更新日期:2018-07-02
  • Zn2SnO4-carbon cloth freestanding flexible anodes for high-performance lithium-ion batteries
    Mater. Des. (IF 4.525) Pub Date : 2018-06-30
    Ji Xia, Ran Tian, Yiping Guo, Qi Du, Wen Dong, Runjiang Guo, Xiuwu Fu, Lin Guan, Hezhou Liu
    更新日期:2018-07-01
  • Study on the embrittlement of flash annealed Fe85.2B9.5P4Cu0.8Si0.5 metallic glass ribbons
    Mater. Des. (IF 4.525) Pub Date : 2018-06-30
    Christian Minnert, Markus Kuhnt, Sebastian Bruns, Amalraj Marshal, Konda Gokuldoss Pradeep, Mie Marsilius, Enrico Bruder, Karsten Durst
    更新日期:2018-07-01
  • Optimization analysis of novel foam-filled elliptical columns under multiple oblique impact loading
    Mater. Des. (IF 4.525) Pub Date : 2018-06-30
    Feng Xiong, Dengfeng Wang, Shengwen Yin
    更新日期:2018-07-01
  • Dissolution mechanisms and kinetics of δ phase in an aged Ni-based superalloy in hot deformation process
    Mater. Des. (IF 4.525) Pub Date : 2018-06-30
    Dao-Guang He, Y.C. Lin, Xing-You Jiang, Liang-Xing Yin, Li-Hua Wang, Qiao Wu
    更新日期:2018-07-01
  • 更新日期:2018-07-01
  • Integration of plasmonic Au nanoparticles in TiO2 hierarchical structures in a single-step pulsed laser co-deposition
    Mater. Des. (IF 4.525) Pub Date : 2018-06-30
    Beatrice Roberta Bricchi, Matteo Ghidelli, Luca Mascaretti, Andrea Zapelli, Valeria Russo, Carlo Spartaco Casari, Giancarlo Terraneo, Ivano Alessandri, Caterina Ducati, Andrea Li Bassi
    更新日期:2018-07-01
  • Creep of closed-cell aluminum foams: Effects of imperfections and predictive modeling
    Mater. Des. (IF 4.525) Pub Date : 2018-06-30
    Bin Han, Run-Pei Yu, Qian-Cheng Zhang, Hua-Jian Gao, Qi Zhang, Tian Jian Lu, Bing-Heng Lu
    更新日期:2018-07-01
  • Hybrid nanomaterials designed for volatile organic compounds sensors: A review
    Mater. Des. (IF 4.525) Pub Date : 2018-06-27
    Rafaela S. Andre, Rafaela C. Sanfelice, Adriana Pavinatto, Luiz H.C. Mattoso, Daniel S. Correa
    更新日期:2018-06-28
  • 更新日期:2018-06-28
  • 更新日期:2018-06-28
  • Role of graphite on microstructural evolution and mechanical properties of ternary TiAl alloy prepared by arc melting method
    Mater. Des. (IF 4.525) Pub Date : 2018-06-28
    Hongze Fang, Ruirun Chen, Yong Yang, Yanqing Su, Hongsheng Ding, Jingjie Guo, Hengzhi Fu
    更新日期:2018-06-28
  • Effect of thermal annealing on stress relaxation and crystallisation of ion beam sputtered amorphous Si1-xGex thin films
    Mater. Des. (IF 4.525) Pub Date : 2018-06-28
    F. Guo, M. Martyniuk, D. Silva, Y. Liu, K. Brookshire, L. Faraone
    更新日期:2018-06-28
  • Thermal modelling of linear friction welding
    Mater. Des. (IF 4.525) Pub Date : 2018-06-23
    P. Jedrasiak, H.R. Shercliff, A.R. McAndrew, P.A. Colegrove
    更新日期:2018-06-25
  • 更新日期:2018-06-25
  • Novel insight into evolution mechanism of second liquid-liquid phase separation in metastable immiscible Cu-Fe alloy
    Mater. Des. (IF 4.525) Pub Date : 2018-06-24
    Shichao Liu, Jinchuan Jie, Bowen Dong, Zhongkai Guo, Tongmin Wang, Tingju Li
    更新日期:2018-06-25
  • Mapping of axial plastic zone for roller bearing overloads using neutron transmission imaging
    Mater. Des. (IF 4.525) Pub Date : 2018-06-24
    A. Reid, I. Martinez, M. Marshall, T. Minniti, S. Kabra, W. Kockelmann, T. Connolley, M. Mostafavi
    更新日期:2018-06-25
  • Enhancement of hardness, modulus and fracture toughness of the tetragonal (Fe,Cr)2B and orthorhombic (Cr,Fe)2B phases with addition of Cr
    Mater. Des. (IF 4.525) Pub Date : 2018-06-22
    Jonathan Lentz, Arne Röttger, Felix Großwendt, Werner Theisen
    更新日期:2018-06-22
  • 更新日期:2018-06-22
  • Robust multi objective optimization of anisotropic yield function coefficients
    Mater. Des. (IF 4.525) Pub Date : 2018-06-19
    Kaushik Bandyopadhyay, Krishnaswami Hariharan, Myoung-Gyu Lee, Qi Zhang
    更新日期:2018-06-22
  • Highly filled elastomeric matrix composites: Structure and property evolution at low temperature carbonization
    Mater. Des. (IF 4.525) Pub Date : 2018-06-19
    D.I. Chukov, A.A. Stepashkin, A.I. Salimon, S.D. Kaloshkin
    更新日期:2018-06-22
  • Sinter structure analysis of titanium structures fabricated via binder jetting additive manufacturing ☆
    Mater. Des. (IF 4.525) Pub Date : 2018-06-21
    Evan Wheat, Mihaela Vlasea, James Hinebaugh, Craig Metcalfe
    更新日期:2018-06-22
  • Polymer-metal-polymer (PMP) multilayer transparent electrode for organic optoelectronics
    Mater. Des. (IF 4.525) Pub Date : 2018-06-21
    Vikas Sharma, Himanshu Sharma, Rishi Vyas, Kanupriya Sachdev
    更新日期:2018-06-22
  • Electroluminescent materials: Metal complexes of 8-hydroxyquinoline - A review
    Mater. Des. (IF 4.525) Pub Date : 2018-06-21
    Devender Singh, Vandna Nishal, Shri Bhagwan, Raman Kumar Saini, Ishwar Singh
    更新日期:2018-06-22
  • 更新日期:2018-06-22
  • Bilayer-rich graphene suspension from electrochemical exfoliation of graphite
    Mater. Des. (IF 4.525) Pub Date : 2018-06-19
    Afkham Mir, Anupam Shukla
    更新日期:2018-06-20
  • Highly sensitive pressure sensors employing 3C-SiC nanowires fabricated on a free standing structure
    Mater. Des. (IF 4.525) Pub Date : 2018-06-19
    Hoang-Phuong Phan, Karen M. Dowling, Tuan Khoa Nguyen, Toan Dinh, Debbie G. Senesky, Takahiro Namazu, Dzung Viet Dao, Nam-Trung Nguyen
    更新日期:2018-06-19
  • Programmable morphing composites with embedded continuous fibers by 4D printing
    Mater. Des. (IF 4.525) Pub Date : 2018-06-18
    Qingrui Wang, Xiaoyong Tian, Lan Huang, Dichen Li, Andrei V. Malakhov, Alexander N. Polilov
    更新日期:2018-06-18
  • Study on design and performance of metal-bonded diamond grinding wheels fabricated by selective laser melting (SLM)
    Mater. Des. (IF 4.525) Pub Date : 2018-06-18
    Chenchen Tian, Xuekun Li, Shubo Zhang, Guoqiang Guo, Liping Wang, Yiming Rong
    更新日期:2018-06-18
  • 更新日期:2018-06-18
  • 3D printing high density ceramics using binder jetting with nanoparticle densifiers
    Mater. Des. (IF 4.525) Pub Date : 2018-06-15
    Pragnya Kunchala, Keerti Kappagantula
    更新日期:2018-06-15
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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