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Abstract

In this work studies of barrier height local values are presented. Distribution of the gate-oxide EBG(x, y) and semiconductor-oxide EBS(x, y) barrier height local values have been determined using the photoelectric measurement methods. Two methods were used to obtain the local values of the barrier heights: modified Powell-Berglund method and modified Fowler method. Both methods were modified in such a way as to allow determination of the EBG(x, y) and EBS(x, y) distribution over the gate area using a focused UV light beam of a small diameter d = 0.3 mm. Measurements have been made on a series of Al-SiO2-Si(n+) MOS structures with semitransparent (tAl = 35 nm) square aluminum gate (1 x 1 mm2). It has been found that the EBG(x, y) distribution has a characteristic dome-like shape, with highest values at the center of the gate, lower at the gate edges and still lower at gate corners. On the contrary, the EBS(x, y) distribution is of a random character. Also, in this paper, both barrier height measurements have been compared with the photoelectric effective contact potential difference fMS(x, y) measurements. These results show good agreement between distribution of the barrier heights EBG(x, y) and EBS(x, y) measurements and independently determined shape of the effective contact potential difference fMS(x, y) distribution.

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Authors and Affiliations

K. Piskorski
H.M. Przewlocki
Keywords Mo2C MoO3 CO NaCl
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Abstract

In this work, influence of NaCl additive on the transformation process of MoO3 to Mo2C under pure CO atmosphere in the range of room temperature to 1170 K was investigated. The results showed that transformation of MoO3 to Mo2C can be roughly divided into two stages: the reduction of MoO3 to MoO2 (the first stage) and the carburization of MoO2 to Mo2C (the second stage). As to the first stage, it was found that increasing the content of NaCl (from 0 to 0.5 wt.%) was beneficial for the increase of reaction rate due to the nucleation effect; while when the content of NaCl increased to 2 wt.%, the reaction rate will be decreased in turn. As to the second stage, the results showed that reaction rate was decreased with the increase of NaCl, which may be due to the formation of low-melting point eutectic. The work also found that morphology of as-prepared Mo2C was irregular and particle size of it was gradually increased with increasing the NaCl content. According to the results, the possible reaction mechanism was proposed.
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Authors and Affiliations

Biao-Hua Que
1
ORCID: ORCID
Lu Wang
1 2
ORCID: ORCID
Bao Wang
3
ORCID: ORCID
Yi Chen
3
ORCID: ORCID
Zheng-Liang Xue
3
ORCID: ORCID

  1. Wuhan University of Science And Technology, Hubei Provincial Key Laboratory For New Processes of Ironmaking and Steelmaking, Wuhan 430081, China
  2. Foshan (Southern China) Institute For New Materials, Foshan 528200, Guangdong, China
  3. Wuhan University of Science and Technology, The State Key Laboratory of Refractories and Metallurgy, Wuhan 430081, China
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Abstract

The addition of hard ceramic particles of nc-(Ti,Mo)C in carbon network into Ti matrix has been proved to be an efficient way to enhance their properties. The purpose of this work was to analyze the corrosion, tribological, mechanical and morphological effects of combining nc-(Ti,Mo)C/C with titanium metal, to create a unique composite via selective laser melting technique (SLM). Composites with different weight percentage (5, 10 and 20 wt %) of ceramic phase were produced. The samples of pure Ti and Ti-6Al-4V alloy were also tested, as a reference. These composites were examined for corrosion resistance in body fluid (artificial saliva solution). Moreover, the properties of titanium composites reinforced with nc-TiC powders were compared. It was stated that mechanical properties were significantly improved with increasing amount of nc-(Ti,Mo)C/C in Ti matrix. In terms of corrosion resistance, the composites showed worse properties compared to pure titanium and Ti-6Al-4V alloy, but better than TiC-reinforced composites.

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Authors and Affiliations

P. Figiel
A. Biedunkiewicz
W. Biedunkiewicz
D. Grzesiak
M. Pawlyta
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Abstract

The paper presents the results of research and analysis of voice data transmission quality in IP packet networks. It analyses mechanisms allowing for the assessment of packet telephony data transmission quality. Possible transmission quality levels and adequate quality metrics, applicable in the recommendations of standardisation organisations, as well as suggested limit values conditioning acceptable voice data transmission quality were indicated and discussed. A packet network model was designed and tested, taking into account VoIP architecture supporting various audio codecs used for voice compression. Transmission mechanisms based on audio codecs G.711, G.723, G.726, G.728 and G.729 were investigated. It was shown that for delay-sensitive traffic which fluctuates beyond its nominal rate, selected codecs have an advantage over others and allow for better transmission quality of VoIP traffic with guaranteed bandwidth and delay.
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Bibliography

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Authors and Affiliations

Dariusz Strzęciwilk
1

  1. Institute of Information Technology, University of Life Sciences, Warsaw, Poland
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Abstract

Code Excited Linear Prediction (CELP) algorithms are proposed for compression of speech in 8 kHz band at switched or variable bit rate and algorithmic delay not exceeding 2 msec. Two structures of Low-Delay CELP coders are analyzed: Low-delay sparse excitation and mixed excitation CELP. Sparse excitation is based on MP-MLQ and multilayer models. Mixed excitation CELP algorithm stems from the narrowband G.728 standard. As opposed to G.728 LD-CELP coder, mixed excitation codebook consists of pseudorandom vectors and sequences obtained with Long-Term Prediction (LTP). Variable rate coding consists in maximizing vector dimension while keeping the required speech quality. Good speech quality (MOS=3.9 according to PESQ algorithm) is obtained at average bit rate 33.5 kbit/sec.

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Authors and Affiliations

Przemysław Dymarski
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Abstract

This paper presents the results of diagnostic examinations conducted on the coils of super-heaters made of 10CrMo9‒10 steel that were operated in industrial conditions at 480°C for 130 thousand hours. The tube was exposed in a coal-fired boiler. The chemical and phase composition of the oxide/deposit layers formed on both sides of the tube walls (outside – flue-gas side and inside – steam side) and their sequence was examined using optical microscopy, scanning electron microscopy with electron backscatter diffraction and energy-dispersive X-ray spectroscopy, and X-ray diffraction. The changes in the mechanical properties caused by corrosion and aging processes were concluded from the hardness measurements. In addition, the nature of cracks in the oxide layers caused by pressing a Vickers indenter was determined. The results of these examinations have shown a high degradation of steel on the flue-gas inflow side and identified the main corrosion products and mechanisms.
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Authors and Affiliations

Monika Gwoździk
1
Christiane Ullrich
2
Christian Schimpf
2
David Rafaja
2
Sławomir Kulesza
3
Mirosław Bramowicz
3

  1. Czestochowa University of Technology, ul. Dabrowskiego 69, 42-201 Czestochowa, Poland
  2. TU Bergakademie Freiberg, Akademiestraße 6, 09599 Freiberg, Germany
  3. University of Warmia and Mazury in Olsztyn, ul. Michała Oczapowskiego 2, 10-719 Olsztyn, Poland
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Abstract

The report presents research efforts on the synthesis of Zn/MoS2 composite coatings by electrochemical reduction from a sulphate-borate bath containing MoS2 powder as a dispersion phase at various concentrations. The structure of the Zn/MoS2 composite coatings was characterised and the effect of MoS2 particles embedded on their microhardness was evaluated. The coatings produced are characterized by a compact, homogeneous structure and a good connection to a steel substrate. The incorporation of MoS2 particles into the zinc matrix has an influence on the structure and morphology of the Zn/MoS2 composite coatings. It was found that the presence of MoS2 particles increases surface roughness along with coating hardness. The incorporation of the MoS2 particles into the zinc matrix slightly improves the corrosion resistance compared to Zn coatings, making the corrosion potential shift towards more electropositive values.

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Authors and Affiliations

K. Szmigielska
M. Trzaska
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Abstract

MoO3 thick film was manufactured by using a thermal spray process (Atmospheric Plasma Spray, or APS) and its microstructure, phase composition and properties of the coating layer were investigated. Initial powder feedstock was composed of an orthorhombic α-MoO3 phase, and the average powder particle size was 6.7 μm. As a result of the APS coating process, a MoO3 coating layer with a thickness of about 90 μm was obtained. Phase transformation occurred during the process, and the coating layer consisted of not only α-MoO3 but also β-MoO3, MoO2. Phase transformation could be due to the rapid cooling that occurred during the process. The properties of the coating layer were evaluated using a nano indentation test. Hardness and reduced modulus were obtained as 0.47 GPa and 1.4 GPa, respectively. Based on the above results, the possibility of manufacturing a MoO3 thick coating layer using thermal spray is presented.
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Authors and Affiliations

Yu-Jin Hwang
1
ORCID: ORCID
Kyu-Sik Kim
1 2
ORCID: ORCID
Jae-Sung Park
3
Kee-Ahn Lee
1
ORCID: ORCID

  1. Inha University, Department of Materials Science and Engineering, Incheon, Korea
  2. Agency for Defense Development, Daejeon, Korea
  3. LT Metal, Seoul, Korea
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Abstract

The objective of this paper is to develop a Non Destructive Testing (NDT) method for the detection and classification of defects in composite materials at a micro level and to devise methodologies to analyse the corrosion resistance behavior using Scanned Electron Microscope (SEM) imagery. The defects on the Stainless Steel – Molybdenum (SS-Mo) Nanocomposite coating is estimated from their Scanning Electron Micrographs by using Image Processing algorithms. For this, the SS-Mo Nano Composite coatings are fabricated using a DC magnetron sputtering process using an indigenously prepared sputtering target. Depositions are carried out on Glass substrate for the evaluation of structural, morphological, chemical composition and corrosion resistance of the coatings prepared under different conditions (deposition of SS at 300°C and RT (Room Temperature); deposition of SS + Mo at 300°C and RT). The structural and compositional analysis performed with X-ray Diffraction (XRD) and Energy-Dispersive X-ray spectroscopy (EDX) has confirmed the formation of Stainless Steel Molybdenum Composite, when the deposition is at 300°C. The SS-Mo composite deposited at 300°C is also observed to yield high corrosion resistance of the order 0.058 mm/year. A novel texture – morphology based image feature descriptor has been proposed for corrosion resistance to evaluate the composite material in a Non-destructive manner. The analysis of SEM image of the developed coatings using the proposed feature along with machine learning algorithm reveals the superior property for SS-Mo coatings deposited at 300°C which is also demonstrated by the laboratory experiments.
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Authors and Affiliations

M.C. Pravin
1
ORCID: ORCID
S. Karthikeyan
2
ORCID: ORCID
S. Sathyabama
3
ORCID: ORCID
Sivaramakrishnan Balaji
4
ORCID: ORCID

  1. Bannari Amman Institute Of Technology, Mechatr Onics, India
  2. Thiagarajar College of Engineering, Mechanical Engineering, India
  3. Thiagarajar College of Engineering, Electronics and Communication Engineering, India
  4. Thiagarajar College of Engineering, Chemistry, India
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Abstract

Thermodynamic optimizations of the ternary Fe-B-Mo system and its binary sub-system B-Mo are presented. The Fe-B-Mo description is then extended to the quaternary Fe-B-Cr-Mo system by assessing the ternary B-Cr-Mo system. The thermodynamic descriptions of the other binaries (Fe-B, Fe-Cr, Fe-Mo, B-Cr, and Cr-Mo) and the other ternaries (Fe-B-Cr and Fe-Cr-Mo) are taken from earlier studies. In this study, the adjustable parameters of the B-Mo, Fe-B-Mo, and B-Cr-Mo systems were optimized using the experimental thermodynamic and the phase equilibrium data from the literature. The solution phases of the system (liquid, bcc and fcc) are described with the substitutional solution model, and most borides are treated as stoichiometric phases or semistoichiometric phases, using a simple two-sublattice model for the latter. The system’s intermetallic phases, Chi, Mu, R, and Sigma (not dissolving boron) as well as boride M3B2, based on a formulation of (Cr,Fe)(Cr,Fe,Mo)2(B)2, are described with a three-sublattice model. Reasonable agreement is obtained between the calculated and measured phase equilibria in all four systems: B-Mo; ­Fe-B-Mo; B-Cr-Mo; and Fe-B-Cr-Mo.

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Authors and Affiliations

Jyrki Miettinen
Ville-Valtteri Visuri
Timo Fabritius
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Abstract

The study investigated the primary structure of the new generation of superalloys based on Co-10Al-5Mo-2Nb and Co-20Ni- 10Al-5Mo-2Nb cobalt. Research on a group of cobalt-based materials was initiated in 2006 by J. Sato [1]. These materials may replace nickel-based superalloys in the future due to their excellent properties at elevated temperatures relative to nickel-based superalloys. The primary microstructure characterisation of the Co-10Al-5Mo-2Nb and Co-20Ni-10Al-5Mo-2Nb alloy are the basic subject of this article. The Co-10Al-5Mo-2Nb and Co-20Ni-10Al-5Mo-2Nb alloy are tungsten free alloys of a new type with the final microstructure based on the Co-based solid solution L12 phase of the Co3(Al,Mo,Nb) type as a strengthened structural element. The analysed alloys were investigated in an as-cast state after a vacuum casting process applied on graphite moulds. The primary microstructure of the alloys and the chemical constituent of dendritic and interdendritic areas were analysed using light, scanning electron and transmission microscopy. Currently, nickel-strengthened γ’ phase steels are still unrivalled in aerospace applications, however, cobalt based superalloys are a response to their existing limitations, which do not allow maintaining the current rate of development of aircraft engines.
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Authors and Affiliations

M. Kierat
1 2
ORCID: ORCID
G. Moskal
1 3
ORCID: ORCID
A. Zieliński
2
ORCID: ORCID
T. Jung
2
ORCID: ORCID

  1. Silesian University of Technology, Institute of Materials Science, 8 Krasińskiego Str., 40-019 Katowice, Poland
  2. Łukasiewicz Research Network – Institute for Ferrous Metallurgy, K. Miarki 12-14, 44-100 Gliwice, Poland
  3. Silesian University of Technology, University Zone of Material Innovation, 8 Krasińskiego Str., 40-019 Katowice, Poland
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Abstract

Liquid Phase Exfoliation (LPE) is a common route to produce two-dimensional MoS2 nanosheets. In this research, MoS2 powder is exfoliated by an ultrasonic probe (sonicator) in a water-ethanol solution. It is reported that MoS2 as a prototype 2D Transition Metal Dichalcogenide, has a band gap that increases with a decreasing number of layers. There are some factors that affect the average band gap energy value and the thickness of the exfoliated flakes. We varied different parameters of the ultrasonic probe like power, pulse percentage and time duration of sonication to investigate the effects on the number of MoS2 layers. Our findings from the UV-Visible spectra, SEM, FESEM and TEM images indicate that the minimum thickness for these samples was acquired at 50% of the input power of the sonicator we used (65 W) and the optimum pulse percentage is 50%. The current study also found that the average amount of band gap increased with an increase in sonication time, and then remained unchanged after 60 minutes.
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Authors and Affiliations

Najme Sadat Taghavi
1
Reza Afzalzadeh
1

  1. Faculty of Physics K.N. Toosi University of Technology Tehran 15418-49611, Iran
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Abstract

The paper presents results of investigation of microstructure and micro-hardness for material of ZnO varistors applied to 110 kV surge arrester and surge arrester counter. The research combined two pairs of varistors, each consisted of one varistor subjected before to operation, while the other one was brand new unit and constituted a reference. All varistors were made of the same material by the reputable manufacture. The tests revealed a different degree of the material degradation for varistors subjected before to operation. This also refers to different degradation mechanism observed for the material of these varistors, if typical effects of degradation of aged ZnO varistors were considered as a reference. Physical state of spinel in the microstructure had a significant impact on the material degradation, however a considerable loosening of the microstructure associated with bismuth oxide was observed too. It was surprising, since the precipitates of the bismuth oxide phase most often showed very good binding to the ZnO matrix and high resistance to associated electrical, thermal and mechanical effects. The degradation effects in the ZnO matrix proved to be limited only.

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Authors and Affiliations

P. Papliński
J. Wańkowicz
H. Śmietanka
P. Ranachowski
Z. Ranachowski
ORCID: ORCID
S. Kudela Jr
M. Aleksiejuk
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Abstract

This study fabricated a WC/T-800 cermet coating layer with Co-Mo-Cr (T-800) powder and WC powder using laser cladding, and analyzed its microstructure, hardness and wear properties. For comparison, casted bulk T-800 was used. Laser cladded ­WC/T-800 cermet coating layer showed circular WC phases in the Co matrix, and dendritic laves phases. The average laves phase size in the cermet coating layer and bulk T-800 measured as 7.9 µm and 60.6 µm, respectively, indicating that the cermet coating layer had a relatively finer laves phase. Upon conducting a wear test, the cermet coating layer added with WC showed better wear resistance. In the case of laser cladded WC/T-800 cermet coating layer, abrasion wear was observed; on the contrary, the bulk T-800 showed pulled out laves phases. Based on the above findings, the WC/T-800 cermet coating layer using laser cladding and the relationship between its microstructure and wear behavior were discussed.
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Bibliography

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Authors and Affiliations

Kyoung-Wook Kim
1
Young-Kyun Kim
1
ORCID: ORCID
Sun-Hong Park
2
Kee-Ahn Lee
1
ORCID: ORCID

  1. Inha University, Dept. Mater. Sci. Eng., Incheon 22212, Republic of Korea
  2. POSCO Technical Research Laboratories, Gwangyang 57807, Republic of Korea
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Abstract

In this study, the effect of the addition of ZrO2 and Al2O3 ceramic powders to Cu-Mo-Cr alloy was studied by examining the physical properties of the composite material. The ceramic additives were selected based on the thermodynamic stability calculation of the Cu-Mo-Cr alloys. Elemental powders, in the ratio Cu:Mo:Cr = 60:30:10 (wt.%), and approximately 0-1.2 wt.% of ZrO2 and Al2O3 were mixed, and a green compact was formed by pressing the mixture under 186 MPa pressure and sintering at 1250°C for 5 h. The raw powders were evenly dispersed in the mixed powder, as observed by scanning electron microscopy. After sintering, the microstructures, densities, electrical conductivities, and hardness of the composites were evaluated. We found that the addition of ZrO2 and Al2O3 increased the hardness and decreased the electrical conductivity and density of the composites.
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Authors and Affiliations

Yeong-Woo Cho
1 2
ORCID: ORCID
Jae-Jin Sim
1 2
ORCID: ORCID
Sung-Gue Heo
1 3
ORCID: ORCID
Hyun-Chul Kim
1 3
Yong-Kwan Lee
1 2
ORCID: ORCID
Jong-Soo Byeon
1 2
ORCID: ORCID
Yong-Tak Lee
1 2
ORCID: ORCID
Kee-Ahn Lee
2
ORCID: ORCID
Seok-Jun Seo
1
ORCID: ORCID
Kyoung-Tae Park
1
ORCID: ORCID

  1. Korea Institute for Rare Metals, Korea Institute of Industrial Technology, 7-50 Songdo-dong Yeonsoo-gu, Incheon 21999, Korea
  2. Inha University, Department of Advanced Materials Engineering, Incheon 22212, Korea
  3. Korea University, Department of Materials Science and Engineering, Seoul 02841, Korea
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Abstract

The electronic, optical and thermoelectric properties of MoS2 nano-sheet in presence of the Ru impurity have been calculated by density functional theory framework with Generalized Gradient approximation. The MoRuS2 nano-sheet electronic structure was changed to the n-type semiconductor by 1.3 eV energy gap. The optical coefficients were shown that the loosing optical energy occurred in the higher ultraviolet region, so this compound is a promising candidate for optical sensing in the infrared and visible range. The thermoelectric behaviors were implied to the good merit parameter in the 100K range and room temperatures and also has high amount of power factor in 600K which made it for power generators applications.
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Authors and Affiliations

Firouzeh Motamad Dezfuli
1
ORCID: ORCID
Arash Boochani
2
ORCID: ORCID
Sara Sadat Parhizgar
1
ORCID: ORCID
Elham Darabi
1
ORCID: ORCID

  1. Department of Physics, Faculty of Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran
  2. Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
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Abstract

This study utilizes Ti-8Nb-4Co alloys added to different proportions of Mo2C powders (1, 3, and 5 mass%) by the vacuum sintering process of powder metallurgy and simultaneously vacuum sinters the alloys at 1240, 1270, 1300, and 1330°C for 1 h, respectively. The experimental results indicate that when 3 mass% Mo2C powders were added to the Ti-8Nb-4Co alloys, the specimens possessed the optimal mechanical properties after sintering at 1300°C for 1 h. The relative density was 98.02%, and the hardness and TRS were enhanced to 69.6 HRA and 1816.7 MPa, respectively. In addition, the microstructure of vacuum sintered Ti-8Nb-4Co-3Mo2C alloys has both α and β-phase structures, as well as TiC precipitates. EBSD results confirm that the Mo 2C in situ produced TiC during the sintering process and was uniformly dispersed in the grain boundary. Moreover, the reduced molybdenum atom acted as a β-phase stabilizing element and solid-solution in the titanium matrix.
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Authors and Affiliations

Shih-Hsien Chang
1
ORCID: ORCID
Kun Jie Liao
1
ORCID: ORCID
Kuo-Tsung Huang
2
ORCID: ORCID
Cheng Liang
1
ORCID: ORCID

  1. National Taipei University of Technology, Department of Materials and Miner al Resources Engineering, Taipei 10608, Taiwan, ROC
  2. National Kangshan Agricultural Industrial Senior High School, Department of Auto-Mechanics, Kaohsiung 82049, Taiwan, ROC
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Abstract

The application of titanium alloys is limited due to their low surface hardness and wear resistance, especially for parts operating under friction and contact loads. One of the most widely used technologies for the thermochemical treatment of titanium alloys is gas nitriding. A new method in this direction is surface plasma gas nitriding using indirect arc plasmatrons operating in a chamber with a controlled nitrogen atmosphere. In the present work, the changes in the phase transformations, microstructure, and surface hardness of titanium alloy Ti-8Al-1Mo-1V after plasma gas nitriding at the power of 18 kW, and 25 kW for a time between 5 and 30 minutes are studied. The plasma gas nitriding with the indirect plasmatron of the titanium alloy produced continuous surface layers. Analysis of the surface showed the presence of TiN and TiO2. The thickness of the plasma gas nitrided layers ranges between 100 μm and 350 μm, depending on the technological parameters.
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Authors and Affiliations

Radostina Yankova
1
ORCID: ORCID
Ludmil Drenchev
1
ORCID: ORCID

  1. Bulgarian Academy of Sciences, Institute of Metal Science, Equipment and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski”, Sofia, Bulgaria
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Abstract

The aim of this paper is to present the procedure test for calibration and validation of the numerical model for X22CrMoV12-1 steel multilayer welding. On the real multilayer weld was described how to arrange the whole experiment in order to obtain not only relevant input data but also verification data. Tests on a specially prepared specimen, welded with 8 beads in 4 layers, allows to determine the actual geometry of the single welded beads, registration of welding thermal cycles and the hardness distribution in successively deposited beads together with determining the heat influence of subsequent layers. The results of the real welding tests were compared with the results obtained from the numerical simulations and extended by the calculated stresses and distortions distributions of the tested specimen. A new, improved hardness prediction algorithm for high-alloy martensitic and bainitic steels was also proposed.

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Authors and Affiliations

T. Kik
ORCID: ORCID
J. Moravec
I. Novakova
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Abstract

In this study, microstructural and crystallographic properties of phase transformations occurring with thermal effect in Fe-XMn-Mo-Si (X = 15.14wt.% ve 18.45wt.%) alloys have been investigated. The effects of (wt.%) Mn rates in the alloy on the characteristics of phase transformations were investigated by using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). SEM and TEM investigations was observed that two different martensite (ε and α') structures were formed in austenite grain. In addition, in TEM observations, the interface regions were selected over the bright field image. Crystallographic orientation relationships were obtained by the analyses of electron diffraction patterns from the interface regions. γ → α' type transformation was observed for α' particle formation, and orientation relationship was found as (1–11)γ // (011)α', [101]γ // [1–11–]α' and, γ → ε type transformation was observed for ε martensite plate formation, and the orientation relationship was found as (1–11–)γ // (0002–)ε, [1–1–0]γ // [2–110]ε. It was noticed that this orientation relationships were compatible with the literature (Kurdjumov-Sachs and Shoji-Nishiyama orientation relationship). Precipitation phase (carbide) formation was observed in microstructure analyses. The changes in the magnetic properties of the alloys having different rates of Mn as a consequence of thermal effect phase transformations was investigated by using Mössbauer Spectroscopy. The internal magnetic field, volume fractions (transformation rates), isomer shift values and magnetic characteristics of the main and product phases were revealed by Mössbauer Spectroscopy. In the Mössbauer Spectrum, it was noticed that ε-martensite and γ-austenite structures showed paramagnetic single-peak, and α'-martensite showed ferromagnetic six-peaks.

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Authors and Affiliations

Osman Armağan
Talip Kirindi
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Abstract

This study investigates the microstructures and the mechanical properties of equiatomic Ti20Mo20Ta20Nb20V20 and non-equiatomic Ti40Mo15Ta15Nb15V15 and Ti60Mo10Ta10Nb10V10 HEAs using X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FE-SEM), and micro-Vickers hardness test. The specimens were fabricated using the vacuum arc remelting (VAR) process and homogenized at a temperature of 1300°C for 4 h in a vacuum atmosphere. The determined thermodynamic parameters, Ω ≥ 1.1, δ ≤ 6.6%, and VEC < 6.87, suggested that the HEAs consisted of BCC solid solutions. XRD patterns of all the HEAs displayed single BCC phases. The difference in the solidification rate led to the micro-segregation associated with the elements Ta and Mo enriched in the dendrite arms and the elements V and Ti in the inter-dendritic regions. The HEA specimens showed a decrease in hardness with higher concentration of Ti element because the intrinsic hardness of Ti is lower as compared to the intrinsic hardness of Nb and Mo.

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Authors and Affiliations

Seongi Lee
Kwangmin Lee
ORCID: ORCID
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Abstract

Co-Cr-Mo based sheet I-WP lattice was fabricated via laser powder bed fusion. The effect of microstructure and the I-WP shape on compressive mechanical response was investigated. Results of compression test showed that yield strength of the sheet I-WP was 176.3 MPa and that of bulk Co-Cr-Mo (reference material) was 810.4 MPa. By applying Gibson-Ashby analytical model, the yield strength of the lattice was reversely estimated from that of the bulk specimen. The calculated strength of the lattice obtained was 150.7 MPa. The shape of deformed lattice showed collective failure mode, and its microstructure showed that strain-induced martensitic transformation occurred in the overall lattice. The deformation behavior of additively manufactured sheet I-WP lattice was also discussed.
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Authors and Affiliations

So-Yeon Park
1
ORCID: ORCID
Kyu-Sik Kim
2
ORCID: ORCID
Bandar Almangour
3
ORCID: ORCID
Kee-Ahn Lee
1
ORCID: ORCID

  1. Inha University, Department of Materials Science and Engineering, Incheon, Korea
  2. Agency for Defense Development, Daejeon, Korea
  3. Interdisciplinary Research Center for Intelligent Manufacturing & Robotics, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabi
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Abstract

In this study, a simple and effective way to fabricate highly porous scaffolds with controlled porosity and pore size is demonstrated. Ti-7Zr-6Sn-3Mo shape memory alloy fibers were prepared through a melt overflow process. The scaffolds with porosity of 65-85% and large pores of 100-700 μm in size were fabricated by sintering the as-solidified fibers. Microstructures and transformation behaviors of the porous scaffolds were investigated by means of SEM, DSC and XRD. The scaffolds were composed of β phase at room temperature. Superelasticity with the superelastic recovery strain of 7.4% was achieved by β↔α” phase transformation. An effect of porosity on mechanical properties of porous scaffolds was investigated by using compressive test. As the porosity increased from 65% to 85%, elastic modulus and compressive strength decreased from 0.95 to 0.06 GPa and from 27 to 2 MPa, respectively.

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Authors and Affiliations

Yeon-Wook Kim
Bagus D. Erlangga
Dalhyun Do
Seong-Min Lee
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Abstract

The present study investigated various thermodynamic parameters, microstructures and electrochemical behaviors of TiMoVCrZr and Ti-rich TiMoVCrZr high-entropy alloys (HEAs) prepared by vacuum arc remelting. The microstructures of the alloys were analyzed using X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM), and potentiodynamic polarization tests. The determined thermodynamic values of the Ω-parameter and the atomic size difference (δ) for the HEAs were determined to be in the range of Ω ≥ 1.1, and δ ≤ 6.6% with valance electron configuration (VEC) ≤ 5.0, suggesting the HEAs were effective at forming solid solutions. XRD patterns of the equiatomic Ti20Mo20V20Cr20Zr20 HEA revealed four phases consisting of the body centered cubic1 (BCC1), BCC2, hexagonal close-packed (HCP), and intermetallic compound Cr2Zr phases. Three phases were observed in the XRD patterns of Ti-rich Ti40Mo15V15Cr15Zr15 (BCC, HCP, and Cr2Zr) and a single BCC phase was observed in Ti-rich Ti60Mo10V10Cr10Zr10 HEAs. The backscattered-electron (BSE) images on the equiatomic Ti20Mo20V20Cr20Zr20 HEA revealed BCC and HCP phases with Cr2Zr precipitates, suggesting precipitation from the HCP solid solution during the cooling. The micro-segregation of Ti-rich Ti60Mo10V10Cr10Zr10 HEAs appeared to decrease remarkably. The alloying elements in the HEAs were locally present and no phase changes occurred even after additional HIP treatment. The lowest current density obtained in the polarization potential test of Ti-rich Ti40Mo15V15Cr15Zr15 HEA was 7.12×10–4 mA/cm2 was obtained. The studied TiMoVCrZr HEAs showed improved corrosion characteristics as compared to currently available joint replacement material such as ASTM F75 alloy.

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Authors and Affiliations

Hocheol Song
Seongi Lee
Kwangmin Lee
ORCID: ORCID

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