bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metallurgical modeling of intergranular HAZ liquation cracking during laser welding newly developed crystallography-dependent aerospace materials. Part I: Spontaneous microcrack repair of microstructure development
Authors: Gao Z G 
Published: March 2020

Abstract
Metallurgical modeling of microcrack self-repair during laser welding of nickel-based superalloys has been properly established. Metallurgical mechanism of crystallographic control self-repair intergranular liquation cracking of heat-affected zone (HAZ) through spontaneous feed of interdendrite liquid beneath the surface is proposed. Self-repair of arterial crack network with dendrite substructure of backfill enables crack resistance amelioration and is dependent on alloying element and heat input. Microstructure development and solidification behavior are controlled to minimize the severe liquation cracking near the fusion boundary by optimization of laser welding conditions through numerical analysis. Liquid healing of incipient cracking in the HAZ through available feeding fluid flow due to accessible to weld pool are sensitive to grain size and weld pool geometry to metallurgically suppress liquation crack, stabilize the primary solidification path and improve the weld integrity, simultaneously. It is revealed that optimum low heat input is favored to reduce liquation cracking. Theoretical predictions are in satisfactory agreement with microanalysis of measurement result indirectly. In addition, this metallurgical modeling is also applicable to other nickel-based superalloys with similar metallurgical properties.
Characteristics of Ni/Au/Ni/Au ohmic contact in a p-AlGaN/GaN semiconductor
Authors: Hu Z F , Li X Y , Zhang Y 
Published: March 2020

Abstract
The low-resistance NiAu/Ni/Au ohmic contact in p-type AlGaN/GaN semiconductor was carefully investigated by electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) after two-step annealing at 550 and 750°C. It is shown that complicate double-direction diffusion and reaction occurred in the metal layer and underlying GaN layer. The four metal stacks of Ni/Au/Ni/Au turned into almost one layer and an intimate relationship established at NiAu/GaN boundary, which should play a primary role in ohmic contact to reduce the contact barrier. At the intimate interface, the metal layer close to the contact was enriched with Ga and Au, and the GaN upper layer was metalized by Au and Ni. Numerous Ni atoms were oxidized and formed dispersive NiO nanoclusters in the metal layer, which might have a hindering effect on upward migration of Ga atoms. Dislocations connected with the contact boundary absorbed interstitial atoms of Au or Ni may serve as channels for current carrier transportation. Thus, a low-resistance p-GaN ohmic contact can be obtained by the above combination of these microstructural characteristics.
Steric hindrance effects of phenoxyimine nickel catalysts in ethylene/propylene polymerization
Authors: Xu D , Dai L , Li F Y , Zhu J X , Chai J K , Zhang Y W 
Published: March 2020

Abstract
A new mononuclear phenoxyimine nickel (II) catalyst with a xanthene skeleton was synthesized and applied to polymerization of ethylene/propylene. Higher activities were achieved in comparison with the catalyst lacking the axial steric hindrance and the catalyst with a synergistic effect. Moreover, the synthetic method was easier than that for the bimetallic catalyst.
Effect of prestrain on storage life for HTPB coating in solid rocket motor
Authors: Du Y Q , Zheng J , Yang Y , Yang T C , Tu X 
Published: March 2020

Abstract
The prestrain thermal accelerated aging tests of HTPB coating at 0%, 3%, 6% and 9% levels were carried out. The variation of maximum elongation of HTPB coating at different aging stages was analyzed. The maximum elongation was selected as the performance characterization parameter, and the aging model of HTPB coating was established. According to the time-temperature equivalence principle, the time conversion relationship between prestrain thermal accelerated aging and effective storage at room temperature was obtained, and the storage life of HTPB coating at room temperature was predicted using this model. The results show that the predicted storage life of HTPB coating at room temperature is 18.64a, 18.08a, 9.24a and 7.44a, respectively, under the aging conditions with prestrains of 0, 3, 6, and 9%. The existence of prestrain will have a significant impact on the storage life of HTPB coating, which should be avoided in actual storage.
Synthesis and testing of defected g-C3N4 with improved photocatalytic activity
Authors: Zheng Y , Li C H , Cai Y Y 
Published: March 2020

Abstract
Graphitic carbon nitride samples with defected structure but larger surface areas were synthesized by adding urea as additive to the thermal decomposition (pyrolysis) of melamine. The pyrolysis was carried out at 600°C in ope-air conditions for 2 hours. The as-prepared samples were compared through detailed characterizations such as SEM, BET, XRD, XPS, FTIR and DRS. It was found out that the addition of urea functioned against the perfection of polymerization, and led to defected structure, which were suggested to be g-C3N4 segments in small crystalline domains. As a result, the formation of the defected structure led to blue-shifts in the optical transitions in the UV-Vis spectral range, as well as larger surface areas. In addition, the photocatalytic activities of the samples were measured by degrading Rhodamine B (RhB) with a concentration of 10 mg/L. It was found out that the samples with defected structure exhibited improved photocatalytic activity.
Cyclic deformation behavior of gradient structured austenitic stainless steels
Authors: Zhou W L , Liu K K , Li Y , Ho H S 
Published: March 2020

Abstract
The cyclic deformation behavior of gradient structured 316L austenitic stainless steels produced by shot-peening is investigated. The experimental results show that for all specimens, the cyclic response exhibits a similar fundamental evolutionary character, i.e., first cyclic hardening then followed by cyclic softening. The presence of a gradient structured surface layer is observed to be capable of accelerating the cyclic hardening process but decelerating the cyclic softening process. It is further suggested that the former can be related to the restricted cyclic hardening ability and the latter to the high plastic deformation uniformity.
The Taguchi orthogonal analysis of Ti6Al4V titanium alloy chip morphology in micro-milling
Authors: Zhang X , Pan X D , Wang G L 
Published: March 2020

Abstract
Micro-milling is an efficient machining method, which is suitable for machining miniaturized titanium alloy parts. In this paper, chip morphology in micro-milling of Ti6Al4V titanium alloy was studied experimentally. An orthogonal experiment was established, in which cutting speed, feed per tooth, and axial depth of cut were chosen as the main influencing factors. The effect of milling parameters on chip morphology was analysed via the Taguchi method. The results strongly indicate that the degree of serration of the chip sharply increases with cutting speed, and then is saturated. The calculations of cooling and formation times of adiabatic shear bands under steady-state cutting conditions implied that the dynamic recrystallization occurred in these bands during the Ti6Al4V titanium alloy in micro-milling.
Study on pervious recycled aggregate fiber-reinforced concrete for airfield pavement
Authors: Novak J , Kohoutkova A , Chylik R , Trtik T 
Published: March 2020

Abstract
For the last several years, the attention has been devoted to the development of eco-friendly construction materials with the aim to reduce the environmental impact of construction. The integral part of this development is to find applications for which the recycled materials could be used efficiently. The presented study deals with the development of recycled aggregate fibre reinforced concrete which is going to be used for an innovative precast concrete pavement system. The system is being developed recently at Czech Technical University in Prague with the aim to provide a system for airfield pavement with rapid construction and recycled material utilization. The investigated material is going to be used for construction of a sub-base course which is underneath a surface course of precast concrete elements. Within the scope of the work, standard laboratory tests were conducted with the aim to observe mechanical properties of recycled aggregate fibre reinforced concrete. The obtained findings showed that the material exhibits ductile behaviour likely due to very long polypropylene fibres used for strengthening concrete matrix. On the contrary, the tested material has low modulus of elasticity in comparison with conventional concrete. Subsequently, the pilot construction of the sub-base course was carried out in order to examine both concrete mixture preparation and concrete course installation in practice. The obtained findings showed that a compaction ratio of the material is about 20%. Moreover, a flat surface of the sub-base course was hard to achieve considering the used manufacturing technology.
The compatibilizer content effect on tensile and flexural properties of PC/ABS blends
Authors: Zhu Z F , Chen B , Wen J , Zhang Q , Yuan S , Yin L 
Published: March 2020

Abstract
In this research, the effect of styrene-maleic anhydride (SMA), methyl methacrylate-butadiene–styrene (MBS) and maleic anhydride-grafted ABS (ABS-g-MAH) compatibilizer on thermal and mechanical properties of polycarbonate (PC) and poly(acrylonitrile–butadiene–styrene) (ABS) blends were studied. PC/ABS blends samples with varying contents of compatibilizer were prepared. With the compatibilizer content increases, the results indicated that the effects of these three compatibilizers on PC/ABS blends are not exactly the same. When the SMA content increases from 5 to 20wt%, the impact strength reduced by about 76% from 43.24 kJ/m2 to 10.20 kJ/m2. The SEM picture indicated that when SMA content exceeds 5wt%, SMA resin begins to aggregate and leading to inadequate interfacial bonding between SMA and PC/ABS phases. The results showed that about 5wt% of ABS-g-MAH can improve the impact strength of the blends by about 113% and have little effect on the tensile and flexural properties. Similarly, when the MBS content reaches about 5wt%, the impact strength of PC/ABS blends is increased by about 112%, but as the MBS content increases to 20wt%, the tensile and flexural properties reduced by about 25%.
Microstructural evolution of Super304H stainless steel during high-temperature creep rupture
Authors: Tian X , Yang B X , Ding L L , Xu H , Li Y M 
Published: March 2020

Abstract
This study is aimed to explore the microstructural evolution of Super304H stainless steel during long-term creep. Creep-rupture specimens of this steel are analyzed via microhardness measurement, metallographic structure observation, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that the matrix structure of the steel was stable during high-temperature stress-rupture test without grain growth. Twin boundaries in austenite gradually disappeared with the prolongation of time, which process was accelerated at higher temperatures. The steel hardness sharply increased in the initial stage of high-temperature stress-rupture test due to the second-phase precipitation, and then gradually dropped with time, due to the coarsening of precipitates. The Cu-rich phase and secondary Nb(C,N) with the size less than 50 nm, and M23C6 were the main precipitated phases in the high-temperature stress-rupture test. This allowed the steel under study to retain a high stress-rupture limit due to the precipitation-strengthening effect. The microstructure aging resulted in the formation of M23C6 chain at the grain boundary and coarsening of M23C6 and primary Nb(C,N) in grains. With the coarsening of precipitated phases, hardness and stress-rupture limit of Super304H stainless steel decreased.
Design and experimental study of magnetically controlled shape-memory alloy sensor
Authors: Lu J , Guo Z Y 
Published: March 2020

Abstract
Magnetically controlled shape-memory alloys (MSMA) are smart materials with shape-memory function and such advantages, as large strain, high response speed and high energy conversion efficiency. This lucrative combination provides a theoretical basis for the design of MSMA sensor, which is also experimentally validated in this study. Based on the inverse effect of MSMA, the overall design of MSMA sensor is carried out. The structure of the sensor is optimized by finite element simulation. The input and output characteristics of the sensor are experimentally verified. Finally, the coil excitation power is reduced, and the output induction voltage of the sensor is increased. The correctness of sensor structure and rationality of optimization are verified.
Microstructure and mechanical properties of 25MnB and 25CrMnB steels: a comparative study for track shoe applications
Authors: Feng K , Zhu Y S , Ma X J , Xu G 
Published: March 2020

Abstract
The microstructure and mechanical properties of 25MnB and 25CrMnB track shoes are studied in this paper. The results show that, after proper heat treatment, both 25MnB and 25CrMnB can meet the requirements of mechanical properties for track shoes. The addition of Cr element refines the microstructure of the steel, so that the grain-size number of the plate portion of the track shoe is refined from 8.5 to 9.5. However, it also increases the hardness, strength, and toughness of steel. The impact toughness of 25CrMnB at room temperature and at 40°C is higher by 12.1 and 27.6% than those of 25MnB, Therefore, 25CrMnB steel is preferable for track shoes applications with large sizes, poor working conditions, and high load-bearing requirements.
Antifungal activity and theoretical study of synthesized pyrazole-imidazole hybrids
Authors: Zinad Dhafer S. , Mahal Ahmed , Shareef Omar A. 
Published: March 2020

Abstract
The density functional theory (DFT) and thermodynamic analyses were applied to study the stability and chemical reactivity of the synthesized CMPIP {2-chloro-4-(4-(1-methyl-1H-pyrazole-4-yl)-1H-imidazole-5-yl) pyridine} and MPIMPPA {4-(4-(1-methyl-1H-pyrazole-4-yl)- 1H-imidazole-5-yl)-N-(4-morpholino phenyl) pyridin-2-amine}. The results concluded that the CMPIP compound is more stable than MPIMPPA. The antifungal study was confirmed that the MPIMPPA has a higher inhibition zone against Aspergillus niger (A. niger), as compared to the standard drug used, while the CMPIP compound showed weaker activity than the positive control.
Effect of Ni and Mo contents on microstructure, magnetic and mechanical properties of Ti(C, N)-based cermets
Authors: Xu X Y , Zheng Y , Zhang G T , Yang Z K , Ke Z , Wu H , Zhou W 
Published: March 2020

Abstract
Ti(C,N)-based cermets were prepared by vacuum sintering. The effect of Ni and Mo contents on microstructure, magnetic and mechanical properties of cermets were investigated using XRD, SEM, EDS, and VSM. The results showed that the proportion of ceramic hard phase decreased gradually, and the core-rim structure became incomplete with Ni content. However, with an increase in Mo content from 6 to 18 wt. %, the thickness of rim phase slightly increased. The complete core-rim structure refined the grain size of cermets, and the particles became the finest when Mo content was about 14 wt. %. The magnetization of cermets increased with Ni content, while their magnetization gradually weakened with Mo content. The deterioration of magnetic properties was caused by the high total content of Mo and Ti alloying elements in the binder phase. Meanwhile, the hardness of cermets decreased, while the TRS initially increased, followed by a gradual decrease with content of Ni. With an increase in Mo content, the hardness and TRS of Ti(C,N)-based cermets increased firstly and then decreased. The fracture toughness of cermets increased with Ni content, while the increasing Mo content reduced the fracture toughness. Due to grain refinement and solid-solution strengthening of the binder phase, the optimal composition of cermet was Ti(C,N)-14Mo-25Ni, whose hardness, TRS, and Kic values were ~90.3 HRA, 2340 MPa and 11.7 MPa·m1/2, respectively.
Preparation and performance of binder jetting porous alumina ceramic
Authors: Huang S J , Ye C S 
Published: March 2020

Abstract
This study examines the effects of zirconium basic carbonate (ZBC) added to alumina powders on the mechanical behavior of binder jetting porous alumina ceramic. ZBC powder is easily decomposed to form zirconia particles and then is deposited in the interparticle void spaces. Green alumina samples were obtained with different ZBC contents of 0~8 wt%. The density, linear shrinkage, bending strength, and microstructural evolution of ceramic parts were analyzed and categorized in different ZBC contents. Results showed that the formation of zirconia particles was dominant and improved the performance of sintered samples. Sintering at 1450°C resulted in a denser Al2O3 part with a comparable bending strength of 75.2 MPa and an accessible linear shrinkage of 10% for the ZBC content range of 0 to 6 wt%. At ZBC content of 8 wt%, the gas generated by ZBC decomposition reduced the sintering density. Therefore, adding 6 wt % ZBC content is the optimal choice for binder jetted porous alumina ceramic.
Effect of Mo content on microstructure and mechanical properties of WCoB-TiC based cermets
Authors: Ke Z , Zheng Y , Sun F , Zhang G T , Zhang J J , Xu X Y , Wu H , Dong Z W , Zhou W 
Published: March 2020

Abstract
The effect of Mo content on microstructure and mechanical properties of WCoB-TiC based cermets fabricated by boronizing sintering reaction was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). Results showed that phase compositions of all the WCoB-TiC cermets with 0 to 20 wt% Mo addition were composed of W2CoB2, TiC, TiB2, and the (211) diffraction peak of W2CoB2 phase was continuously shifted towards a high angle with Mo content, indicating that (W, Mo)2CoB2 solid solutions in cermets with 5-20 wt% were formed. Moreover, the cores of W2CoB2 grains were enriched in Mo, while rims of W2CoB2 grains had a relatively lower Mo content, resulting in the formation of a core/rim structure. As Mo content increased, the porosity gradually dropped, while the relative density continuously increased, due to the improved wettability of liquid phase in the hard phase. In addition, average grain sizes dropped initially and then rose gradually with Mo content. An increase in average grain sizes was due to the coalescence and growth of hard-phase particles. The WCoB-TiC cermet with an 10 wt% Mo addition showed excellent comprehensive mechanical properties with a transverse rupture strength of 815 MPa, a Rockwell hardness of 93.4 HRA, and a fracture toughness of 12.5 MPam1/2, respectively.
Stability analysis and numerical simulation of a composite laminated piezoelectric rectangular plate system
Authors: Chen S P 
Published: March 2020

Abstract
This paper investigates the stability behavior in three-degree-freedom composite laminated piezoelectric rectangular plate system based on the Routh-Hurwitz criterion and the normal form theory. Firstly, the stability behavior of the composite laminated piezoelectric rectangular plate is determined by applying the Routh-Hurwitz criterion. Then, the normal forms of the composite laminated piezoelectric rectangular plate systems for the case of one non-semi-simple double zero and two pairs of pure imaginary eigenvalues are obtained by using the normal form theory. Finally, numerical simulations are carried out to illustrate the main results.
Failure analysis of low-carbon steel pipe clamp of pressure pipe
Authors: Huang L Y , Zhang F , Zhong F P , Yuan M 
Published: March 2020

Abstract
A real case of breakage of several pipe clamps used in the pressure pipe hanger is investigated. In order to examine the cause of failure, various techniques, including element analysis, mechanical testing, optical and scanning electron microscopy, component analysis, and impact testing were used. It was found that the fractures of the pipe clamps occurred at the transition zone between a straight and arc segments, the finite element analysis has shown that the transition had the highest stress concentration. The surface deformation during pipe clamp manufacturing process caused hardness rising and toughness descending, resulting in surface cracks, Under the combined effect of lower ambient temperature and service stress, the surface cracks expanded rapidly and the pipe clamps fractured finally. Improvements in the molding process and the use of appropriate quality control measures can eliminate this problem.
Ultra-low temperature effect on electron beam welding process
Authors: Xiao Q S , Han X , Pei Y F 
Published: March 2020

Abstract
In recent years, electron beam welding has become the most important application technology for space welding and plays an important role in the orbital assembly and repair of spacecraft at home and abroad. In this paper, the combination of simulation calculation and experimental verification is used to design the welding deformation control process scheme and related fixtures for ultra-low temperature environment, and the deformation test verification study of welding/repair is carried out. TC4 welding and repairing weld static strength, the tensile strength reaches 90% of the strength of the base metal, and the micro-hardness is basically the same. It provides reference and reference for the future application of electron beam welding technology in space in China.
Pressureless sintering of cordierite ceramics with optimized strength and thermal expansion
Authors: Cao J W , Shi X M , Jiao Y F , Zhang C , Li Z P , Zheng Y , Cheng Y Y , Ren L H 
Published: March 2020

Abstract
In this study, cordierite ceramic samples with very low thermal expansion are prepared by the pressureless sintering technique. The effects of sintering temperature and holding time on their sintering density and elastic modulus are investigated, while their optimal values are assessed as 1420°C and 1 h, respectively. These parameters ensure the elastic modulus of 121GPa, the relative sintering density corresponding to 95% of the theoretical value, and the coefficient of thermal expansion of |4.4|ϗ 10−7 °C.
A method of constitutive experiment for accurate description of tube performance under rotary-draw bending
Authors: Zhu Y X , Chen R , Wang Y , Tu W B , Liu Y L 
Published: March 2020

Abstract
Establishing accurate constitutive relations is an important prerequisite for improving the springback prediction accuracy of rotary-draw bending of tubes. In this paper, the stress loading paths are studied for rectangular tube and composite circular tube in rotary-draw bending processes. It is found that there is reverse loading with tangential/circumferential stress for both the rectangular tube and the base/covered tube of composite circular tube. And the reverse loading is in the plastic deformation range. Two constitutive experimental schemes are designed according to the above research results: (1) The constitutive experiment is designed according to the variation of stress peak points of the tube with the bending process and the yield state of the material. The calculation method of the loading force F is given, too. (2) The displacement of the beam of the tensile tester is determined according to the corresponding strain during stress fluctuations, and an example is given to illustrate how the displacement of the beam is calculated according to the strain corresponding to each trajectory point. The calculation formula of the beam displacement during repeated loading, unloading and reverse loading is developed, too.