bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Tensile Shear Strength for Lap Joint of Dissimilar Steels
Authors: Takashima Yasuhito , Washio Tomo , Minami Fumiyoshi
Published: January 2021

The influence of different thickness combinations was investigated on the strength of the lap joint of dissimilar steels. In this study, lap joints of dissimilar steels were welded by laser welding. The tensile shear test was conducted for the lap joints. Rotational deformation process around the weld bead of the lap joint was observed by a digital video camera during the test. Motion analysis from the video of the tensile shear test indicated that the rotation angle around the weld bead was reduced by overlapping higher strength grade steel. Three-dimensional elastic-plastic finite element analysis was performed for the tensile shear test of the lap joint. The numerically calculated deformation behavior of the lap joint subjected to tensile shear loading showed reasonable agreement with the experimental record. It was found that the rotation angle was reduced and tensile shear strength of the lap joint increase by overlapping higher strength grade steel sheet.
Effect of the Pre-Strain on the Elastic Behavior of a Dual-Phase Steel with Different Martensite Contents
Authors: Wallner Matthias , Schneider Reinhold , Steineder Katharina , Krizan Daniel , Hebesberger Thomas , Larour Patrick
Published: January 2021

The modulus of elasticity is an important parameter for an accurate prediction of the springback in sheet metal forming processes. With increasing plastic deformation, this modulus behaves nonlinearly and declines, which leads to an unpredictable springback behavior. The most cited reason for this nonlinearity is the dislocation movement during plastic deformation that especially occurs with multiphase steels. The present contribution investigates the nonlinear unloading behavior and the resulting decrease of the elastic modulus from a differently heat treated DP980 steel. The heat treatments set five different microstructures with martensite volume fractions in the range of 42 to 95 %. By means of the tensile test, a decline of the elastic modulus according to pre-strain was examined by evaluating the chord-modulus during unloading at different strain levels. In addition, a nano-hardness test was performed. It turned out that in all heat treatment conditions, a pronounced decrease in the modulus of elasticity up to 25% from the initial value occurred. With decreasing annealing temperature and lower martensite volume fraction, respectively, the martensite hardness increased, leading to higher hardness differences between the ferrite and the martensite phase in the microstructure. This led to an increase of strain hardening, i.e. to an increased formation of fresh mobile dislocations in the vicinity of the harder martensite phase during plastic deformation. As a result, the modulus of elasticity decreased more sharply. Thus, in the present contribution, an interplay between the martensite volume fraction and its hardness on the decrease of elastic modulus could be clearly manifested.
Adhesion Properties of Thin Film Multilayers: Comparison of Nanoindentation and Four-Point-Bending Techniques
Authors: Walter Thomas , Zareghomsheh Mohammad , Khatibi Golta , Danninger Herbert
Published: January 2021

In this study, we investigated the adhesion strength of SiO2/SiN/TiW/Cu film stacks on silicon by the use of cross-sectional nanoindentation (CSN) technique. The delamination occurred along the SiN/TiW interface as determined by means of SEM and EDX analysis. The critical energy release rate was determined as a quantitative measure of the adhesion strength by application of analytical models as well as Finite Element Method (FEM). Comparative measurements on samples of the same layer composition using the well-established four-point bending (4PB) technique were performed to validate the results of the CSN measurements. FEM was performed to calculate the loading conditions and stress distribution in the samples. The calculations also allowed separating the contribution of plastic and elastic energy in the metallization layers during delamination testing and thereby estimating the value of the interfacial adhesion energy. The experimental results show the good applicability of both the 4PB and CSN method for determining quantitative values of the fracture toughness of thin-film interfaces found in microelectronic components and indicate a good agreement between the two methods.
Effect of Strain Rate on Compressive Behavior of a ZrCuNiAl Bulk Metallic Glass at Room Temperature
Authors: Guo Zhi Ping , Wang Chuan Ting , He Yong , He Yuan , Guo Lei , Hu Xue Bing , Lan Si
Published: January 2021

In this study, quasi-static and dynamic compression tests were performed on a ZrCuNiAl bulk metallic glass. The results demonstrated that the ZrCuNiAl bulk metallic glass changed from plastic deformation without strain rate effect to brittle fracture with negative strain rate sensitivity. The fracture surface morphology was related to the strain rate and temperature rise. The modified cooperative-shear model was determined to describe the effect of strain rate and temperature rise on the yield stress of ZrCuNiAl bulk metallic glass.
Syngas Production by Dry Methane Reforming over Mg Doped NiO-ZrO2 Catalysts
Authors: Wang Ye , Wang Yan Nan , da Costa Patrick , Hu Chang Wei
Published: January 2021

In producing syngas, which offers environmental benefits, dry reforming of methane (DRM) could promote the installation of the future carbon tax. This reaction has been already extensively studied and nowadays, no stable catalysts are enough efficient to scale up the process to its industrialization. It has been suggested that basic sites can affect the performance of catalyst. It is known that magnesium promotes the performance of catalyst. In order to understand the effect of Mg for dry reforming of methane, NiO-MgO-ZrO2 catalysts were studied. The activity was carried out at 700 °C in a fixed-bed micro-reactor under CH4:CO2:Ar=1:1:8. It was shown that the introduction of Mg led to an unexpected decrease in the activity when compared to non-promoted catalyst. It was also shown that the surface area, pore-volume, pore diameter, and weak basicity decreased when the Mg was introduced into NiO-ZrO2 catalyst. All these properties can cause a decrease in the activity, selectivity, and stability of NiO-MgO-ZrO2 catalyst for DRM.
Study of the Microstructure and Mechanical Properties Obtained by Laser Boost in SLM Process for the Ti-64 Alloy
Authors: Widomski Caroline , Solas Denis , Brisset François , Helbert Anne Laure , Baudin Thierry , Lebel Sébastien
Published: January 2021

Selective laser melting (SLM) is one of the new additive manufacturing techniques in which complex parts can be created directly by selectively melting layers of powder. If the productivity of the process is too fast, defects (porosity, partially melted powder, spatters …) are generated inside the fabricated parts and can deteriorate the mechanical properties of the product. A new Laser Boost strategy with a larger melting area and a productivity of 43.20 cm3/h has been compared to a Linear Classic strategy. Ti-64 alloy samples were elaborated with both strategies to study their influence on microstructure and mechanical properties. Laser Boost strategy leads to the formation of Ti-64 prior β grains that are larger than the Linear Classic strategy. Mechanical properties obtains are similar with both strategies with a maximum strength average around 1250MPa and an elongation at failure between 3 and 9%. A thermal post-processing by Hot Isostatic Pressure have been carried out on samples made by Laser Boost to increase the ductility of the material up to 15%.
Investigation on Surface Roughness in Electron Beam Selective Melting by Mesoscale Model
Authors: Wu Chao Chao , Zafar Muhammad Qasim , Zhao Hai Yan
Published: January 2021

Modeling and simulation in meso-scale have been used to investigate the complicated physics involving powder behaviors during the forming process in electron beam selective melting. But it is difficult to quantitatively predict the forming quality of parts due to the huge calculation amount for multi-layer and multi-pass cases. In this paper, we presented a novel frame for investigating the side surface roughness of fabricated components based on single-track simulation. An integrated model of selective beam melting with considering the random distribution powder particles was developed. The surface morphologies of simulated tracks were used to calculated the surface roughness, and the calculated results were validated by experiment data from independent literature. The effects of heat input were discussed in detail. It reveals that the side roughness increases with a lower heat input. The mechanism behind is the fluctuation of tracks induced by the asymmetry of molten pool, which is related to the coalescence of melting particles and unevenness of powder distribution.
Static Recrystallization in Aluminum/Graphene Composites
Authors: Wu Xiao Dong , Liu Xiao Li , Cao Ling Fei , Huang Guang Jie
Published: January 2021

The aim of this work was to analyze the recrystallization behavior of cold rolled Aluminum/graphene composites during annealing. The Aluminum/graphene composite was cold rolled firstly, and then annealed at different temperature (250°C, 300°C, 350°C, 400°C) and for various time (1 h, 2 h, 8 h, 32 h). Full recrystallization did not occur until the annealing temperature was above 300 °C. With annealing temperature increasing from 250 to 300°C, the hardness of the composites decreased from 49.6 to 27.6 HV. Grain growth were not observed at high annealing temperature and longer annealing time, which suggested that Graphene has strong pinning effect on the grain boundary of Aluminum.
Investigation of the Role of Intermetallic Phases in Microstructure of UFG Titanium VT8M-1 Alloy
Authors: Yakovleva Tatyana Vitalyevna , Dyakonov Grigory , Stotskiy Andrey , Modina Iuliia Mikhailovna , Semenova Irina P.
Published: January 2021

The paper studies the microstructure of two-phase ultrafine-grained titanium VT8M-1 alloy (Ti-5.7Al-3.8Mo-1.2Zr-1.3Sn), which was obtained by rotary swaging (RS). Parameters of the microstructure and the change of the phase elemental / chemical composition were investigated by scanning electron microscopy and transmission electronic microscopy. It was shown that the silicide particles like S2 - (Ti,Zr)6Si3 were precipitated in the process of rotary swaging. The influence of silicide precipitations on the characteristics of high temperature strength of the ultrafine-grained two-phase titanium VT8M-1 alloy was discussed in the paper. The alloy microstructure was analyzed after the creep-rupture tests in the operation temperature range 300-400oС.
Effect of Chemical Composition on Grain Refinement of AlxCoCrFeNi High Entropy Alloys with NiAl Grain Boundary Precipitates
Authors: Yasuda Hiroyuki Y. , Miyamoto Hiroyuki , Inagaki Takuya , Cho Ken , Nagase Takeshi
Published: January 2021

In AlxCoCrFeNi high entropy alloys (x = 0.3–0.5), the NiAl phase with the B2 structure is precipitated rapidly along the fcc grain boundaries. During recrystallization after conventional cold rolling, the NiAl precipitates effectively suppress the grain growth, which results in the ultrafine-grained microstructure. It should be noted that no severe plastic deformation is necessary to obtain the microstructure. The volume fraction of the NiAl precipitates increases with increasing x. As a result, the average grain size of the fcc matrix (dm) after the recrystallization decreases with increasing x, and therefore, a minimum dm of 0.5 μm can be obtained at x = 0.5. The grain refinement by the NiAl precipitates is consistent with the Zener-Smith model. At x = 0.5, the alloy with dm = 0.5 μm exhibits a yield stress of 1163 MPa and an elongation of 24% at room temperature.
Improvement of Mechanical Properties of Laminated Composites by Using Cryogenic Roll Bonding
Authors: Yu Hai Liang , Liu Juan , Wang Lin
Published: January 2021

Laminated metal composites are composed of alternating layers of metals or alloys, bonding together at their interface, which have gained extensive attention because of their advantages such as improved fracture toughness, impact behavior, corrosion, wear and damping capacity. Roll bonding is the most widely used method to process many metallic composites. In this study, we fabricated some kinds of Al/Ti/Al sandwich-like laminated composites by cryogenic roll bonding. We find that cryogenic roll bonding techniques can improve the mechanical properties of laminated composites. Finally, we will discuss the mechanism of improvement in bonding strength and mechanical properties.
Numerical Simulation of Microstructure Evolution during Continuous Hot Rolling Process of GCr15 Steel Rod
Authors: Zhang Liwen , Li Fei , Zhang Chi , Mao Pei Gang , Li Fei
Published: January 2021

In this paper, the microstructure evolution during continuous hot rolling process of GCr15 steel rod was investigated. A series of multi-field coupled finite element models were established based on commercial finite element software MSC.Marc. The kinetics equations of austenite grain size evolution of GCr15 steel were coupled to these models by a designed MSC.Marc subprogram. The field variables, including temperature, equivalent stress, equivalent strain, and equivalent strain rate, were calculated. The distributions of dynamic recrystallization, metadynamic recrystallization, and static recrystallization fractions were investigated. The distribution and evolution of austenite grain size at different stages in the continuous hot rolling process were analyzed. To verify the models, the temperatures of GCr15 steel rod at different stages in the continuous hot rolling process were measured. And the austenite grain sizes at cross section of the rod after the continuous hot rolling process were measured. The simulation results show a good agreement with the experimental results.
Effect of Tempering Time on Microstructure and Mechanical Properties of SA738 Gr.B Steel
Authors: Li Yan Mei , Zhang Shu Zhan , Jiang Zai Wei , Yu Sheng , Ye Qi Bin , Yang Meng Qi , Xi Yan Hong
Published: January 2021

The effect of tempering time on the microstructure and mechanical properties of SA738 Gr.B nuclear power steel was studied using SEM, TEM and thermodynamic software, and its precipitation and microstructure evolution during tempering were clarified. The results showed that SA738 Gr.B nuclear power steel has better comprehensive mechanical properties after tempering at 650 °C for 1h. With the extension of the tempering time, M3C transformed into M23C6 with increasing size, which affected the yield strength and impact energy. When the tempering time is 8h ~ 10h, due to the transformation of M3C to M23C6, the composition of matrix around the carbide changed, causing the temperature of Ac1 dropped, forming twin-martensite which deteriorated the impact toughness of the steel.
The Microstructure and Properties of Low Carbon PM 625 Alloy for Marine-Based Application
Authors: Zheng Liang , Zhang Guo Qing , Xu Xiu Qing , Li Zhou
Published: January 2021

The low carbon content powder metallurgy (PM) 625 alloy were manufactured by vacuum induction gas atomization (VIGA) and hot isostatically pressing (HIP) for marine-based application such as parts in the subsea Xmas tree. Corrosion experiment was performed in simulated deep seawater and subsea oil & gas service environment. The microstructures and properties of low carbon 625 alloy were comparably investigated with that of the as-cast alloy. The results indicated that the dendritic arm spacing (DAS) of the as-cast 625 alloy is 2 orders of magnitude higher than that of the powders, whereas the HIPed alloys possess a fine equiaxed grain structures without dendritic segregation and an average grain size of 14.5μm. No minor phase has been found beside the γ matrix in the original powders with different particle size. The tensile strength of low carbon PM 625 alloy is 26% higher than that of as-cast 625 alloy. PM 625 alloy possesses an excellent corrosion resistant in simulated deep seawater and oil & gas service environment for 30 days.
The Effect of Deformation Strain on Texture Uniformity in Tantalum Sheet during Asymmetric Cross Rolling
Authors: Zhu Jia Lin , Liu Shi Feng , Long Dou Dou , Liu Ya Hui , Zhou Shi Yuan , Zhang Jing
Published: January 2021

Microstructure and crystallographic texture play an important role in the sputtering target properties. The effect of asymmetric cross rolling (ACR) and deformation strain during ACR on texture homogeneity is not clear. Thus, high-purity tantalum (Ta) plates were ACR to 60% and 87% reduction in thickness. Texture of the rolled Ta sheets in the surface and center layer are characterized via X-ray diffraction (XRD). The XRD results indicate that ACR is effective to weaken the texture gradient existing in the as-received Ta plate. Besides, more homogeneous texture distribution along the thickness can be obtained with the increasing strain during ACR process.
Effects of Powder Microscopic Defects on Densification and Mechanical Properties of WC via Spark Plasma Sintering
Authors: Zhu Liu , Wang Jin Fang , Tu Zhi Biao , Xue Na , Li Wei Wei
Published: January 2021

The WC composite powder was synthesized by a new specific chemical activation technique. A large number of lattice defects such as surface humps, dislocations and stacking fault exist in the surface of the WC powder after chemical activation technique. By using such activated WC powder, the binderless WC cemented carbide with high density (15.54 g/cm3), super hardness (average 26.29 GPa) and excellent fracture toughness (8.9 MPa.m1/2) can be fabricated by SPS at 1700 °C and 50 MPa pressure. The improvement in density, hardness and fracture toughness are respectively 4.5%, 15.3% and 17.1% compared to when using the original WC powder. This improvement is because microscopic defects on the surface of the WC powder can greatly improve surface free energy of the powder, which improves the sintering activity and reduces the sintering temperature of the WC powder.
Spark Plasma Sintering of Paper-Derived Ti3AlC2-Based Composites: Influence of Sintering Temperature
Authors: Syrtanov Maxim , Kashkarov Egor , Murashkina Tatyana , Travitzky Nahum
Published: January 2021

This paper describes the influence of sintering temperature on phase composition and microstructure of paper-derived Ti3AlC2 composites fabricated by spark plasma sintering. The composites were sintered at 100 MPa pressure in the temperature range of 1150-1350 °C. Phase composition and microstructure were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The multiphase structure was observed in the sintered composites consisting of Ti3AlC2, Ti2AlC, TiC and Al2O3 phases. The decomposition of the Ti3AlC2 phase into Ti2AlC and TiC carbide phases was observed with temperature rise. The total content of Ti3AlC2 and Ti2AlC phases was reduced from 84.5 vol.% (1150 °C) to 69.5 vol.% (1350 °C). The density of composites affected by both the content of TiC phase and changes in porosity.
The Application of Neutron Diffraction Techniques (NDT) in Measuring Residual Strain-Stresses of Engineering Materials
Authors: Ma Yan Ling , Zhang Shu Yan , Zhang Peng , Paddea Sanjoo , Gong Zhi Feng , Gao Jian Bo , Zhan Xia , Wang Chen , Chu Ming Qiang , Bian Fang , Wang Yao
Published: January 2021

In order to quantitatively understand the residual strain distributions and benefits of engineering components following special technique treatment, such as Autofrettaging, Hot Isostatic Pressing (HIP) and Dissimilar Material Welding (DMW), the Neutron Diffraction Technique (NDT) has been employed recently to measure residual strain and stress distributions on following three cases of (a) Autofrettaged Aluminum 7075 high pressure vessels; (b) Hot Isostatic Pressed (HIPPED) heavy metals of tungsten clad in tantalum plate and (c) Dissimilar Material Welding (DMW) of 316L austenitic stainless steel and ferritic steel AS508 with Alloy 52 weld filler. This paper reports the recent research findings, including (a) NDT can identify optimal Autofrettage pressure level, by which load bearing capacity of the Autofrettaged pressure vessel increased by 215MPa; (b) NDT is able to reveal residual strains within heavy metals of Tungsten clad in Tantalum plate HIPPED and (c) NDT revealed a maximum residual tensile hoop stress value of about 494MPa in the interface between parent material SA508 and the weld seam. This is vital information for the post weld process and subsequent safe use of the dissimilar materials weld. Other researchers’ successful examples of working with NDT are also briefly reviewed. Future prospective of Engineering Materials Diffractometer (EMD) at CSNS is described too with a view to demonstrating the application and importance of NDT in revealing residual strain-stresses that are inevitable within engineering materials and engineering components following any manufacturing process.
Hardness Prediction of AA 2024-T3 FSW Weld
Authors: Galisson Sébastien , Carron Denis , Le Masson Philippe , Stamoulis Georgios , Feulvarch Eric , Surdon Gilles
Published: January 2021

The hardness of AA 2024 is mainly dependent of the precipitation state in the material. This one will vary through the process of friction stir welding (FSW) which generates heat and deformations. The most important effect will be the thermal excursion which greatly affects the nature and the distribution of precipitates and so the mechanical properties of the material. Three Myhr & Grong-type submodels have been used in this study in order to simulate the variation of hardness in AA 2024-T3 FSW welds. These models allowed to simulate the hardening by growth of S-precipitates and the softening by coarsening and dissolution of GPB zones / co-clusters or S-precipitates. Finally, the natural ageing was taken into account following the Robson model. The complete model has been calibrated with isothermal data found in the literature and still has to be optimised. Nevertheless, preliminary results show the coherence of the model when performed on isothermal data. The model has been also applied to predict FSW hardness profiles that are compared to those found in the literature.
Density Functional Theory Study of the Adsorption of Metal Adatoms on Graphene
Authors: Nunomura Norio , Yamashita Jun , Sunada Satoshi
Published: January 2021

In this study, we investigated the influence of the interaction between graphene and other materials as a basis for controlling the electronic structure of nanocarbon materials. First-principles calculations based on density functional theory (DFT) were performed on the optimized structure, adsorption energies and electronic states when copper and aluminum atoms were placed on graphene. As a result, we found that copper and aluminum are stable at the bridge and the hollow site, respectively. It was found that the adsorption energy of aluminum atom on graphene is larger than that of copper atom. It is considered that the difference in adsorption energy is caused by the difference in the dominant electron orbitals of the copper atom and the aluminum atom.
Investigation of CGHAZ Simulations of Low-Carbon Bainitic Steels
Authors: Nyo Tun , Kaijalainen Antti , Hannula Jaakko , Kömi Jukka I.
Published: January 2021

The effect of ten different combinations with various amounts of niobium (0-0.6 wt.%) and chromium (1-4 wt.%) on weldability and mechanical properties of thermomechanically rolled and direct-quenched low-carbon (0.035 wt.%) microalloyed bainitic steel were investigated. Two compositions were alloyed with boron to increase the hardenability, and two with titanium to improve the toughness properties in heat affected zone. The target of the study was to produce steel with 700 MPa yield strength combined with good impact toughness. Coarse grained heat affected zone (CGHAZ) simulations were performed using the Gleeble 3800 thermomechanical simulator to evaluate the weldability of the investigated steels using cooling time from 800 °C to 500 °C (t8/5) of 5 s and 15 s to simulate different heat inputs in actual welding procedure. Microstructures were characterized using light optical microscopy, and hardness profiles of simulated heat affected zones were determined as well as Charpy-V impact toughness at-40 °C and-60 °C. Shorter t8/5 time (5 s) produced generally better impact toughness properties compared to longer t8/5 -time (15 s). Steels with 4 % Cr had the highest impact energies. Generally, more softening occurred with longer t8/5-time (15 s). However, Cr and Nb alloying decreased the amount of softening in the CGHAZ region, especially with longer t8/5 -time. These results indicate that even with higher t8/5 -time, it is possible to achieve strength properties equivalent to the base material in the CGHAZ region by Cr and Nb alloying.
Experimental Characterization and Modelling of the PLC Effect in an AlMg-Alloy
Authors: Xu Jian Bin , Holmedal Bjørn , Hopperstad Odd Sture , Marthinsen Knut
Published: January 2021

In the present work, uniaxial tension tests have been conducted to study the mechanical response of a commercial Al4.5wt%Mg alloy (AA5182). The measurements range from the strain rate of 10-4 to 100 s-1 at room temperature. Digital image correlation (DIC) is also utilized to characterize the heterogeneous deformation of PLC localization. An extremely high camera frame rate (1000Hz) is applied to accurately measure the critical strain of instabilities, especially for tests at high strain rates (>10-1 s-1). The objective of this work has been to evaluate currently existing constitutive and physically based models to see to which extent they can match the experimental findings related to dynamic strain aging, i.e. stress-strain curves, work hardening behavior and critical strain behavior.
Development of New Particle Method Based on MPS and its Applicability for Friction Stir Welding of Dissimilar Joint
Authors: Serizawa Hisashi , Mitsufuji Kenta , Miyasaka Fumikazu
Published: January 2021

Friction stir welding (FSW) is one of the solid-state welding and it has been widely employed for joining aluminum alloys. In addition, as a result of R&D efforts about FSW tool, this method is expected to join the steels and/or various dissimilar materials. In order to examine the thermal and mechanical behavior in FSW, many numerical studies have been conducted and the heat generation behavior near FSW tool is precisely demonstrated by using the moving particle semi-implicit (MPS) method which is one of the particle method. In this research, in order to reduce the computational time, a new parcel method based on MPS is developed and its applicability is examined for simulating the friction stir welded dissimilar joint between V-ally and austenite stainless steel SUS316L. From the serial computational results, it is revealed that the influence of rotational speed on the heat generation during FSW seems to be larger than that of traveling speed. Moreover, the numerical result indicates that the sound dissimilar joint might be fabricated when V-alloy is set to be the retreating side (RS), the FSW tool is inserted in RS and the rotational speed increased appropriately although the two materials have not been joined in this welding condition of FSW experimentally.
PL Properties of (Ba, Ca)2( Si, P)O4: Eu Synthesized by Various Annealing and Cooling Process
Authors: Ando Shota , Nakano Hiromi , Fukuda Koichiro
Published: January 2021

We have been investigating the series of P doped Ca2SiO4 (C2S) using Eu2+ or Eu3+ as activator with various colors. The crystal structure of C2S is particularly easily controlled by heating because the established polymorphs of C2S are, in the order of increasing temperature, γ, β, α’L, α’H, and α. In order to control the crystal structure, the phosphors were synthesized and then annealed at temperatures 1473 K-1773 K. The crystal structures and PL properties were compared between slow cooling and quenching (cooled in water). We found unique phenomena when the phosphors were treated by quenching process. In the case of (Ba1-xCax)2(Si0.94P0.06)O4:Eu3+ ( 0.25 ≤ x ≤ 1), color emission changed from red to blue-white for the phosphor with a high concentration of Ba and quenched at 1773 K. In general, Eu3+ doped phosphors showed the red emission color in any host materials. However, Ba-included and quenched-treatment phosphors emitted a bright white color. The mechanism and relationship between the PL property and crystal structure were characterized carefully using X-ray diffraction, electron microscope and X-ray absorption fine structure.
Microstructural Prediction of Heat Treated Steel Forgings for Severe Applications
Authors: Anelli Ettore , Lucchesi M. , Chugaeva A.
Published: January 2021

An in-house 2D finite volume model, specific for components of simple shape, was developed and applied to predict the thermal and microstructural evolution during heat treatment of steel forgings. The results of the thermal metallurgical modelling, including hardness profiles through the thickness, were compared with the experimental ones. Moreover, the 3D FEM software Deform-HT, able to calculate the thermal and microstructural evolution and the stress field during quenching, was specialized for the cases of interest. Examples of optimal heat treatment to develop the target microstructure and strength and reduce the risk of quenching cracks are discussed.
Thermal and Magnetic Properties of Ternary Fe-B-C and Quaternary Fe-B-C-Si Alloys with High Glass-Forming Ability and High Magnetization
Authors: Bitoh Teruo , Hibino Takafumi , Koshiba Hisato
Published: January 2021

The thermal and magnetic properties of the ternary Fe-B-C and quaternary Fe-B-C-Si amorphous alloys have been investigated. It has been discovered that the ternary Fe-B-C amorphous alloys with compositions close to Fe79.3B14.3C6.4 exhibit a glass transition prior to crystallization on heating. The alloys also have high mass magnetization of 176–178 A m2/kg at room temperature. In addition, the glass-forming ability (GFA) of the alloys is significantly enhanced by the addition of 4 at% Si while maintaining high magnetization of approximately 170 A m2/kg at room temperature. In was found that the Fe23(B, C)6 phase (Cr23C6-type) is formed during crystallization of the quaternary Fe-B-C-Si alloys with the large GFA. It was also confirmed that the amorphous powders of Fe-Cr-B-C-Si alloys could be produced by a conventional water atomization method and exhibit the low core losses of 305–362 kW/m3 at 100 kHz and 100 mT. The quaternary Fe-B-C-Si amorphous alloys with high GFA, high magnetization and low core losses are suitable for a core material of various magnetic components.
High Purity Magnetite Microparticles Directly Derived from Mill Scale via Hydrogen-Reduction Method
Authors: Boontanom Autchariya , Suwanpinij Piyada
Published: January 2021

This study develops a fast and simple way to produce high purity magnetite (Fe3O4) microparticles from mill scale by using hydrogen reduction with the addition of vapour as a retarding agent. By optimising the reduction temperature and gas flow rate, the characterisations by X-ray diffractometry technique shown that the Fe3O4 fraction of over 93 wt.-% is shown at the reduction temperature of 550 – 650 oC with the flow rate of the 4.5-5.5 mol%H2 + Ar gas + H2O gas mixture from 100 – 200 ml/min. The highest Fe3O4 fraction of over 99 wt.-% can be achieved from the reduction with the mixed gas at 650 oC and the flow rate of 200 ml/min for 4 hour.
Multi-Scale Characterization by Neutronography and Electron Diffraction of Ni Coating on Cu-Ni-Al or Cast-Iron Glass Molds after Laser Cladding
Authors: Bourahima Fazati , Helbert Anne Laure , Ott Frédéric , Ji Vincent , Rege Michel , Brisset François , Courteaux Arnaud , Baudin Thierry
Published: January 2021

Laser cladding of a Ni based powder on Cu-Ni-Al or cast iron was performed with a 4kW continuous Nd: YAG laser. The Cu-Ni-Al and cast-iron substrates are used for their thermal properties in glass mold industry. But the issue of these materials is their lack of resistance on corrosion and abrasion. The role of the Ni based alloy is to protect the mold without affecting its thermal properties (Heat Affected Zone (HAZ)). The purpose of this research is to produce a well bonded Ni based melted powder without pores or cracks on a non-planar surface (curvilinear section). An investigation of the impact of the processing parameters, power (1500-3200 W), scanning speed (2.5-10 mm/s) and powder feeding rate (24.5-32.5 g/min) on the bonding quality, the porosity propagation and HAZ appearance is performed. The used methods are neutronography, Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Electron BackScatter Diffraction (EBSD). These multi-scale techniques are obviously complementary. Neutronography is a well-adapted non-destructive method to observe the porosity in the volume thanks to the contrast between materials. EBSD analysis allows us to analyze the microstructural evolution of the coating notably by observing the dendrites growth. This same method also permits to observe the HAZ nature according to the laser cladding parameters. Those methods allowed to optimize the processing parameters in a way to obtain perfect bonding, to avoid porosity propagation and to limit the HAZ emergence.
Effect of Distance along the Built Axis on Mechanical Properties and Microstructure in Al10SiMg SLM Alloy
Authors: Cerri Emanuela , Ghio Emanuele
Published: January 2021

It is know that rapid solidification promotes solid solubility larger than at equilibrium, in association with very fine grains and eutectic microstructures. Consequently, the precipitation behaviour in additive manufacturing alloys can be quite different from that of alloys quenched after a solution treatment and aged. In this study, Al10SiMg samples were produced by Selective Laser Melting (SLM) while keeping the table at 150°C continuously during the job. The effect of temperature on mechanical properties of the samples was investigated as function of time or distance along the built axis (300 mm). The hardness behaviour was measured by micro Vickers indentations and significant inhomogeneities were detected along the built axes. These results were also confirmed by tensile property values. The tensile strength varied of 80 MPa from the bottom to the top of the sample. The microstructure was investigated by optical and scanning electron microscopy; the observations showed variable precipitate distributions that justify the mechanical response along the built axis.
Hot and Cold Deformation Behaviors and Microstructure Evolutions of Mn18Cr18N Austenitic Stainless Steel with High-Nitrogen
Authors: Chen Hui Qin , Tian Ji Hong , Li Fei , Qin Feng Ming , He Wen Wu
Published: January 2021

Hot and cold deformation behavious and microstructure evolutions of Mn18Cr18N were investigated by thermo-mechanical modeling experiments and microstructure analysis. The results show that hot deformation flow stress curves characterized by the same work hardening and subsequent stress softening varied with temperatures and strain rates for both of as-cast and as-forged samples. And flow stresses are sensitive to strain rate. At strain rates lower than 0.01s-1, the flow stresses are lower, and microstructure evolution controlled by dislocation mechanism dynamic recrystallization; At strain rates higher than 0.1s-1, the flow stresses are higher, and microstructure evolution controlled by twinning mechanism dynamic recrystallization. But the dynamic recrystallzed fraction of the as-cast sample was much less than that of the as-forged sample. For cold deformation, the simple uniaxial tensile sample shows that the monotone increasing flow stress curve and monotone decreasing work-hanrdening rate. However, for the uniaxial and biaxial compression-tensile samples with different previous compression, the subsequent tensile yield stress, the maximum tensile stress, the reduction of cross sectional area and the elongation have extremums respectively at the previous compressive deformation of about 25%-30%. Microstructure evolution mechanisms during cold deformation were planar slipping and twinning.
Microstructure Evolution in an Advanced High Strength Steel under Continuous Cooling
Authors: Chen Shang Ping , Mostert Richard , Aarnts Maxim
Published: January 2021

The present work was undertaken to understand the phase transformation behaviour in a third generation steel 0.22C-2.1Mn-1.0Si during continuous cooling. The microstructure at various cooling rates were examined by using different techniques, such as optical microscopy, scanning electron microscopy, dilatation test and X-ray measurement. The results show that the amount of bainite that forms during continuous cooling is limited and there is a bainitic transformation stop temperature for this kind of steels. A continuous cooling transformation diagram of the steel is established.
Thermal Stability of Ultrafine-Grained Pure Titanium Processed by High-Pressure Torsion
Authors: Chen Wan Ji , Xu Jie , Liu De Tong , Shan De Bin , Guo Bin , Langdon Terence G.
Published: January 2021

High-pressure torsion (HPT) was conducted under 6.0 GPa on commercial purity titanium up to 10 turns. An ultrafine-grained (UFG) pure Ti with an average grain size of ~96 nm was obtained. The thermal properties of these samples were studied by using differential scanning calorimeter (DSC) which allowed the quantitative determination of the evolution of stored energy, the recrystallization temperatures, the activation energy involved in the recrystallization of the material and the evolution of the recrystallized fraction with temperature. The results show that the stored energy increases, beyond which the stored energy seems to level off to a saturated value with increase of HPT up to 5 turns. An average activation energy of about 101 kJ/mol for the recrystallization of 5 turns samples was determined. Also, the thermal stability of the grains of the 5 turns samples with subsequent heat treatments were investigated by microstructural analysis and Vickers microhardness measurements. It is shown that the average grain size remains below 246 nm when the annealing temperature is below 500 °C, and the size of the grains increases significantly for samples at the annealing temperature of 600 °C.
Study on the Effect of V Microalloying on Earthquake Resisting High-Strength Reinforcing Bar Steels
Authors: Chung Junho , Kim Taeh Yung , Lee Ju Sang
Published: January 2021

Recently, the frequency of earthquakes has been increasing worldwide. As a result, steel reinforced with seismic performance that can satisfy the social needs to strengthen the existing seismic performance of existing infrastructure facilities and new buildings has become important. In general, to secure the yield strength of reinforcing bars and to reduce the production cost, reinforcing bars are produced by rolling the surface through a facility such as a Tempcore. In Korea, most of them have adopted the Tempcore process to ensure the mechanical requirements of the product. However, the use of a small amount of alloying elements and the application of Tempcore have limitations in producing reinforcing bars that require seismic performance. In recent years, remarkable progress has been made in the production and application of high strength rebars. Microalloying and fine-grain strengthening are the most effective methods in developing high strength rebars. That is, the precipitation of V (C, N) is promoted by the addition of V to improve the strength by precipitation strengthening of V-carbonitride. However, in V-microalloyed reinforcing bars, it was confirmed that the required strength did not increase proportional to the amount of V added. In this study, the effects of vanadium and other alloying elements on the mechanical properties and yield ratio of steel bars were investigated by tensile test results and microstructural evaluation.
Effect of Different Production Processes on Metallic Composite Phase Change Materials for Thermal Energy Storage
Authors: Confalonieri Chiara , Gariboldi Elisabetta
Published: January 2021

Phase Change Materials (PCMs) can be applied in Thermal Energy Storage and Thermal Management systems, exploiting the storage and release of latent heat associated to a phase transition. Among them, metallic PCMs can be used at medium and high temperatures (i.e. above 150°C), storing higher heat per unit volume at higher temperatures with respect to the most widely investigated polymeric and salt-based PCMs. Miscibility Gap Alloys (MGAs) can be used to obtain multiple-phase mixtures in which the active phase (the actual PCM) is mixed to a second, high-melting temperature phase, with negligible interaction between them. These can actually be considered as fully metallic composite materials specifically developed for thermal management. Suitable microstructures can prevent leakage of active phase when the solid-liquid transition occurs, resulting in a form-stable PCM (FS-PCM). However, obtaining these microstructures it is not trivial. The present study focuses on a solid-liquid FS-PCM consisting of a ‘classical’ fully metallic FS-PCM, an Al-Sn based MGAs produced by powder metallurgy. The goal was to evaluate the effect of different production processes on thermal and mechanical behaviour of the PCM. Particularly, powder metallurgy routes including both simple mixing and ball milling were compared and further combined. Moreover, several compression and sintering conditions were considered, also substituting Al powders with Al-alloy powders, in order to optimize the material microstructures in view of suitable thermal and mechanical properties. Finally, the casting route with a rapid solidification approach was investigated for the same alloy.
Challenges in Printing Certified Additive Manufactured Material: Ensuring Process Stability and Material Quality
Authors: de Bruycker Evy , Hautfenne Céline , Thielemans Fabien , Nardone Steve
Published: January 2021

Additive manufacturing (AM) is currently one of the most promising and advanced tools to make high-end components. For industrial acceptance of these components, there is a demand for the delivery of high quality parts, certified under recognized standards. Pre-requisites for such certified parts are the certification of the powder feed-stock and the use of qualified facilities. Such a certification and qualification project encompasses different challenges regarding both powder testing and print process stability. Today there are insufficient quantitative acceptance criteria for AM metal powders in the standards. The main challenge is determining which properties to test and how to define some key indicators that can guarantee consistent quality of the end product. To face this challenge several relevant powder properties were tested in order to link powder performance to the properties of the printed material. To guarantee process stability and repeatability, a good knowledge and control of the different process parameters and their influence on the material quality is needed. Hence, an extensive study on the homogeneity of properties over the 3D printer platform was performed. A qualification testing platform was designed to guarantee and periodically check the quality of the printed AM316L material. The proper procedures and parameter settings were determined and fixed. This methodology finally lead to the qualification of the ENGIE Laborelec Powder Lab and the ENGIE Fabricom AM printing facility and the certification of AM 316L material through a recognized external qualification body. This initiative paves the way to ensure industrial acceptance of the selective laser melting process for high quality applications.
Statistical Errors in X-Ray Triaxial Stress Analysis by Cos α Method
Authors: Ejiri Shoichi , Ohba Hiroaki , Sasaki Toshihiko
Published: January 2021

Currently, the sin2ψ method is established as an effective technique as how to measure the residual stress state of metal materials non-destructively by X-ray diffraction. In recent years, new X-ray stress measurements with two-dimensional detector are developed and spreading in the world. There is the cosα method as one of the new techniques. However, the research about the statistical errors in the method continues. The measurement theory of the cos α method is reviewed on the triaxial stress state. The triaxial stress analysis by the method is examined and discussed from a viewpoint of the derived errors for the determination.
Thermal Stability of Retained Austenite in Advanced TRIP Steel with Bainitic Ferrite Matrix for Automotive Industries
Authors: El-Shenawy Eman , Refaiy Hoda , Nasr El-Din Hoda
Published: January 2021

Multiphase steels consisting of retained austenite and martensite/bainite microstructures such as TRIP, low-temperature-bainite, and Q&P steels are attractive candidates for the new-generation of AHSS. These steels exhibit a remarkable combination of strength and toughness which is essential to meet the objective of weight reduction of engineering-components, while maintaining the compromise of tough-safety requirements. Such good mechanical properties are due to the enhanced work hardening rate caused by austenite-to-martensite transformation during deformation and the strengthening contribution of martensite/bainite. The retained austenite can thermally decompose into more thermodynamically stable phases as a consequence of temperature changes, which is referred to as the thermal stability of retained austenite. TRIP-aided steel is an effective candidate for automotive parts because of safety and weight reduction requirements. The strength–ductility balance of high strength steel sheets can be remarkably improved by using transformation induced plasticity behavior of retained austenite. In manufacturing hot rolled TRIP-aided sheet steels, austenite transforms into bainite during the coiling process. Because black hot coils cool slowly after the coiling process, they are exposed at about 350–450°C for a few hours or days. Therefore, the metastable residual austenite can be decomposed into other phases. This decomposition of residual austenite can produce serious deteriorate of mechanical properties in hot rolled TRIP-aided sheet steels. The present work identified the decomposition behavior and study the thermal stability of retained austenite in the TRIP-aided steel with bainitic/ferrite matrix depending on coiling temperatures and holding times by means of DSC and XRD analysis.
3d Printer Heads for Extrusion of Biologicals Gels
Authors: Engels Andreas , Schlegel Volker , Jacobs Hannes , Großelindemann Niklas , Morshed Md Niaz , Stenglein Antonia , Bonaiuto Vincenzo , Foitzik Andreas H.
Published: January 2021

Processing biological materials with 3-dimensional (3D) printers has attracted increasing interest in several research areas. At the same time, off-the-shelf solutions are increasingly available in a wider variety to meet the current market demand. However, most of the available bioprinters are closed source, thus, modifications are quite challenging or require an avoidable consultation process with the manufacturer. Furthermore, the entry prices for basic machines amount to several thousands of euros. Whereas, high-end 3D bio printers with a vast array of features are available for several hundred thousand euros. Due to the immense potential of this tool in the field of biotechnology it is important to extend the availability of this technology for research purposes in terms of adaptability and price. This ongoing work focuses on open-source 3D printer heads with the ability to extrude biological materials. The print heads include several techniques to process low as well as high viscose biomaterials such as agar and gelatin. Additionally, obstacles such as continuous substrate tempering or integration into existing 3D printers are addressed. The work presented is open source and thus freely adaptable to any user’s specific needs. Our goal is to process a diverse range of biomaterials with different print techniques.