14 pages, 8080 KiB  
Article
Predictive Simulation of Plastic Processing of Welded Stainless Steel Pipes
by Riccardo Rufini, Orlando Di Pietro and Andrea Di Schino *
Dipartimento di Ingegneria, Università di Perugia, Via G. Duranti 93, 06125 Perugia, Italy
Metals 2018, 8(7), 519; https://doi.org/10.3390/met8070519 - 5 Jul 2018
Cited by 40 | Viewed by 5614
Abstract
Metal forming is the most used technique to manufacture complex geometry pieces in the most efficient way, and the technological progress related to the various application fields requires increasingly higher quality standards. In order to achieve such a requirement, people are forced to [...] Read more.
Metal forming is the most used technique to manufacture complex geometry pieces in the most efficient way, and the technological progress related to the various application fields requires increasingly higher quality standards. In order to achieve such a requirement, people are forced to perform quality and compliance tests finalized to guarantee that these standards are met; this often implies a waste of material and economic resources. In the case of welded stainless steel pipes, several critical points affecting the general trend of subsequent machining need to be taken into account. In this framework, the aim of the paper is to study the effects of different process parameters and geometrical characteristics on various members of the stainless steel family during finite elements method (FEM) simulations. The analysis of the simulation outputs, such as stress, strain, and thickness, is reported through mappings, in order to evaluate their variation, caused by the variation of the simulation input parameters. The feasibility of the simulated process is evaluated through the use of forming limit diagrams (FLD). An experimental validation of the model is performed by comparison with real cases. Major parameters that mainly guide the outcome of the simulations are highlighted. Full article
(This article belongs to the Special Issue Modelling and Simulation of Sheet Metal Forming Processes)
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14 pages, 6514 KiB  
Article
Effect of Rolling Reduction on Microstructure and Property of Ultrafine Grained Low-Carbon Steel Processed by Cryorolling Martensite
by Qing Yuan, Guang Xu *, Sheng Liu, Man Liu, Haijiang Hu and Guangqiang Li
The State Key Laboratory of Refractories and Metallurgy, Hubei Collaborative Innovation Center for Advanced Steels, Wuhan University of Science and Technology, 947 Heping Avenue, Qingshan District, Wuhan 430081, Hubei, China
Metals 2018, 8(7), 518; https://doi.org/10.3390/met8070518 - 5 Jul 2018
Cited by 28 | Viewed by 4006
Abstract
A novel method of cryorolling martensite for fabricating ultrafine grained low-carbon steel with attractive strength was proposed. The results indicate that ultrafine-grain structured steel could be manufactured by cryorolling and the subsequent annealing of martensite. The mean ferrite size of 132.0 nm and [...] Read more.
A novel method of cryorolling martensite for fabricating ultrafine grained low-carbon steel with attractive strength was proposed. The results indicate that ultrafine-grain structured steel could be manufactured by cryorolling and the subsequent annealing of martensite. The mean ferrite size of 132.0 nm and the tensile strength of 978.1 MPa were obtained in a specimen with a reduction of 70% in thickness. There were peak value and valley value in the strength and grain size of ferrite with the increase of reduction from 50% to 80%, respectively. The further growth of ferrite grain at 80% reduction is attributed to the heavier distortion energy at large reduction, which activates the secondary recrystallization of ferrite. Furthermore, the distribution of ferrite grains became more uniform with increasing of reduction from 50% to 70%. Additionally, the amount of lamellar dislocation cell substructure increased with the reduction at liquid nitrogen temperature. Full article
(This article belongs to the Special Issue Processing-Structure-Property Relationships in Metals)
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15 pages, 3233 KiB  
Article
Calix[4]arene-Based Amino Extractants Containing n-Alkyl Moieties for Separation of Pd(II) and Pt(IV) from Leach Liquors of Automotive Catalysts
by Manabu Yamada 1,*, Yu Kaneta 2, Muniyappan Rajiv Gandhi 3, Uma Maheswara Rao Kunda 1 and Atsushi Shibayama 3
1 Research Center of Advanced Materials for Breakthrough Technology, Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita 010-8502, Japan
2 Graduate School of Engineering Science, Akita University, 1-1 Tegatagakuen-machi, Akita 010-8502, Japan
3 Graduate School of International Resource Sciences, Akita University, 1-1 Tegatagakuen-machi, Akita 010-8502, Japan
Metals 2018, 8(7), 517; https://doi.org/10.3390/met8070517 - 5 Jul 2018
Cited by 11 | Viewed by 4273
Abstract
Pt, Pd, and Rh platinum group metals (PGMs) are utilized in automotive catalytic converters to reduce the level of harmful gas emissions. To evaluate the separation efficiencies of PGMs from the leach liquors of automotive catalysts, their extractabilities from both single-component solutions and [...] Read more.
Pt, Pd, and Rh platinum group metals (PGMs) are utilized in automotive catalytic converters to reduce the level of harmful gas emissions. To evaluate the separation efficiencies of PGMs from the leach liquors of automotive catalysts, their extractabilities from both single-component solutions and leach liquors were determined using three p-dialkylaminomethylcalix[4]arenes (alkyl: n-hexyl~n-octyl; 3–5) as extractants, and the obtained results were compared with the data of acyclic p-di-n-octylaminomethyldimethylphenol (6) and those previously reported for macrocyclic calix[4]arene- and thiacalix[n]arene-based amine and amide extractants. Various extraction parameters, including the contact time, HCl concentration, and concentrations of Pd(II) and Pt(IV) ions, were examined, and the distributions and stoichiometry ratios of the recovered Pd(II) and Pt(IV) species were calculated. All macrocyclic extractants 3–5 exhibited high and selective extractabilities of Pd(II) and Pt(IV) ions contained in the leach liquors of automotive catalysts. The E% values of 3–5 from the leach liquors were 94.2, 93.0, and 97.7 for Pd(II) and 91.7, 94.0, and 92.5 for Pt(IV), respectively. Acyclic compound 6 did not perform well even though higher ratios of extractant used. Furthermore, the results of reusability testing demonstrated relatively large extractability values obtained for these two metals even after five extraction/stripping cycles. Full article
(This article belongs to the Special Issue Solvent Extraction of Critical Metals)
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16 pages, 13287 KiB  
Article
An Efficient Powder Metallurgy Processing Route to Prepare High-Performance β-Ti–Nb Alloys Using Pure Titanium and Titanium Hydride Powders
by Bhupendra Sharma 1,*, Sanjay Kumar Vajpai 2 and Kei Ameyama 3
1 Department SI2M, Microstructures et Contraintes, Institute Jean Lamour, University of Lorraine, 54011 Nancy, France
2 Department of Metallurgical & Materials Engineering, National Institute of Technology Jamshedpur, Jharkhand 831014, India
3 Department of Mechanical Engineering, College of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu-City, Shiga 525-8577, Japan
Metals 2018, 8(7), 516; https://doi.org/10.3390/met8070516 - 4 Jul 2018
Cited by 13 | Viewed by 5412
Abstract
Toward designing a cost-effective advanced powder metallurgy approach, we present a new insight into the efficient utilization of titanium hydride powder, together with pure Ti powder, to prepare high-strength β-titanium alloys. In the present work, Ti–40 mass% Nb alloy was prepared by mechanical [...] Read more.
Toward designing a cost-effective advanced powder metallurgy approach, we present a new insight into the efficient utilization of titanium hydride powder, together with pure Ti powder, to prepare high-strength β-titanium alloys. In the present work, Ti–40 mass% Nb alloy was prepared by mechanical alloying of a mixture of pure Ti, titanium hydride, and Nb elemental powders, followed by a carefully designed two-step spark plasma sintering. The role of relative amounts of titanium hydride and pure Ti powders during mechanical alloying, and their effect on the microstructural and mechanical properties of the Ti–40Nb alloy, have been discussed and elaborated. An increasing amount of titanium hydride results in higher powder yield and smaller resultant powder particle size. Subsequent two-step spark plasma sintering resulted in equiaxed microstructure with primarily β phase, wherein the grain size decreased with increasing amounts of titanium hydride powder. The specimen corresponding to alloys prepared using equal amounts of pure Ti and titanium hydride powders resulted in fine-grained structure, exhibiting the best combination of mechanical properties, that is, a combination of highest hardness, high strength, and high ductility. Full article
(This article belongs to the Special Issue Spark Plasma Sintering-A Key Technology towards the Development of New Materials)
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8 pages, 2330 KiB  
Article
Mn3O4 Octahedral Microparticles Prepared by Facile Dealloying Process as Efficient Sulfur Hosts for Lithium/Sulfur Batteries
by Yan Zhao 1, Yuan Tian 1, Xiaomin Zhang 1, Zhifeng Wang 1,*, Taizhe Tan 2, Zhihong Chen 3,* and Yichao Wang 4
1 School of Materials Science and Engineering, Research Institute for Energy Equipment Materials, Hebei University of Technology, Tianjin 300130, China
2 Synergy Innovation Institute of GDUT, Heyuan 517000, China
3 Shenyang Institute of Automation, Chinese Academy of Sciences, Guangzhou 511458, China
4 School of Life and Environmental Sciences, Deakin University, Waurn Ponds, VIC 3216, Australia
Metals 2018, 8(7), 515; https://doi.org/10.3390/met8070515 - 4 Jul 2018
Cited by 4 | Viewed by 3657
Abstract
A facile and industry-accepted dealloying method was used to synthesize Mn3O4 particles, which were then employed to prepare sulfur/Mn3O4 (S/Mn3O4) composites as cathode materials for lithium-sulfur batteries. The composites delivered initial discharge capacity [...] Read more.
A facile and industry-accepted dealloying method was used to synthesize Mn3O4 particles, which were then employed to prepare sulfur/Mn3O4 (S/Mn3O4) composites as cathode materials for lithium-sulfur batteries. The composites delivered initial discharge capacity reaching up 1184 mAh·g−1 at 0.1 C with capacity retention of 679 mAh·g−1 after 150 cycles. In addition, even at 2 C, the lithium/sulfur battery with S/Mn3O4 cathode delivered high reversible discharge capacity of 540 mAh g−1, demonstrating excellent rate capability. Full article
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11 pages, 4941 KiB  
Article
Thermal Stability of Ru–Al Multilayered Thin Films on Inconel 617
by Yung-I Chen *, Zhi-Ting Zheng and Jia-Wei Jhang
Institute of Materials Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan
Metals 2018, 8(7), 514; https://doi.org/10.3390/met8070514 - 4 Jul 2018
Cited by 8 | Viewed by 3307
Abstract
Ru-riched and equiatomic Ru–Al multilayered thin films were fabricated on Si and Inconel 617 substrates. These thin films exhibited a multilayered structure that is caused by stacking cyclical gradient concentration through cosputtering. X-ray diffraction analysis indicated that the as-deposited Ru–Al multilayers comprised Ru [...] Read more.
Ru-riched and equiatomic Ru–Al multilayered thin films were fabricated on Si and Inconel 617 substrates. These thin films exhibited a multilayered structure that is caused by stacking cyclical gradient concentration through cosputtering. X-ray diffraction analysis indicated that the as-deposited Ru–Al multilayers comprised Ru and RuAl phases. Oxidation that is caused by annealing atmospheres and elements diffused from substrates was investigated. The results indicated that the inward diffusion of O at 600 °C in a 1% O2–99% Ar atmosphere was restricted by the formation of an amorphous Al-oxide sublayer, and inward diffusion of O at 800 °C in air was limited by the formation of a crystalline Al2O3 scale. Additionally, the outward diffusion of elements from Inconel 617 penetrated the unoxidized parts of the 800 °C–annealed Ru–Al multilayers. Full article
(This article belongs to the Special Issue Metal and Metal-Oxide Film Deposition)
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10 pages, 1680 KiB  
Article
Evaluation of Surface Characteristics and Hemocompatibility on the Oxygen Plasma-Modified Biomedical Titanium
by Hsi-Jen Chiang 1,2, Hsin-Hua Chou 2,3, Keng-Liang Ou 4,5,6,7,8,9, Erwan Sugiatno 8, Muhammad Ruslin 10, Rahmat Abd Waris 2,6, Chiung-Fang Huang 4,11, Chung-Ming Liu 12,13,* and Pei-Wen Peng 11,*
1 Graduate Institute of Biomedical Materials and Tissue Engineering, College of Biomedical Engineering, Taipei Medical University, Taipei 110, Taiwan
2 School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan
3 Dental Department of Wan-Fang Hospital, Taipei Medical University, Taipei 116, Taiwan
4 Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan
5 Department of Dentistry, Taipei Medical University-Shuang Ho Hospital, New Taipei City 235, Taiwan
6 Department of Prosthodontic, Faculty of Dentistry, Hasanuddin University, Makassar 90245, Indonesia
7 School of Dentistry, Health Sciences University of Hokkaido, Hokkaido 061-0293, Japan
8 Department of Prosthodontic, Faculty of Dentistry, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia
9 3D Global Biotech Inc., New Taipei City 221, Taiwan
10 Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Hasanuddin University, Makassar 90245, Indonesia
11 School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan
12 School of Dentistry, College of Medicine, China Medical University, Taichung 404, Taiwan
13 Biomedical Technology R & D Center, China Medical University Hospital, Taichung 404, Taiwan
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Metals 2018, 8(7), 513; https://doi.org/10.3390/met8070513 - 3 Jul 2018
Cited by 20 | Viewed by 4383
Abstract
Oxygen plasma with different treatment powers and durations was utilized to modify the biomedical pure titanium (Ti) surface in the present study. The superficial, microstructural and biological properties of the plasma-oxidized samples were investigated using the electron microscopy, X-ray photoemission spectroscopy, grazing incidence [...] Read more.
Oxygen plasma with different treatment powers and durations was utilized to modify the biomedical pure titanium (Ti) surface in the present study. The superficial, microstructural and biological properties of the plasma-oxidized samples were investigated using the electron microscopy, X-ray photoemission spectroscopy, grazing incidence X-ray diffractometer, contact angle goniometer and blood clotting time assay. During different treatment powers and durations, the island-like nanostructural rutile-TiO2 layer and dimple-like nanostructural rutile-TiO2 layer were generated on the surfaces of the plasma-oxidized samples, respectively. It was also found that the plasma-oxidized sample with a rough oxide layer resulted in the formation of a higher wettability. Moreover, the blood clotting time assay indicated that the plasma-oxidized samples exhibited the adhesion behaviors of red blood cells. As the Ti surface underwent plasma oxidation at 280 W for 30 min, it not only generates a rough nanostructural rutile-TiO2 layer, but also presents an excellent hemocompatibility. Therefore, these findings demonstrate that oxygen plasma modification is a potential approach to promote the hemocompatibility of biomedical pure Ti surface. Full article
(This article belongs to the Special Issue Surface Treatment Technology of Metals and Alloys)
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13 pages, 4977 KiB  
Article
Characteristics of Welding and Arc Pressure in the Plasma–TIG Coupled Arc Welding Process
by Bo Wang 1,2, Xun-Ming Zhu 3, Hong-Chang Zhang 4,*, Hong-Tao Zhang 1,2,* and Ji-Cai Feng 1
1 State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China
2 Institute for Shipwelding Technology, Shandong Institute of Shipbuilding Technology, Weihai 264209, China
3 Weihai Wanfeng Magnesium Science and Technology Development Co., Ltd., Weihai 264209, China
4 Department of Electrical Engineering, Harbin University of Science and Technology, Rongcheng, 264300, China
Metals 2018, 8(7), 512; https://doi.org/10.3390/met8070512 - 3 Jul 2018
Cited by 15 | Viewed by 8671
Abstract
In this article, a novel hybrid welding process called plasma-TIG (Tungsten Inert Gas welding) coupled arc welding was proposed to improve the efficiency and quality of welding by utilizing the full advantage of plasma and TIG welding processes. The two arcs of plasma [...] Read more.
In this article, a novel hybrid welding process called plasma-TIG (Tungsten Inert Gas welding) coupled arc welding was proposed to improve the efficiency and quality of welding by utilizing the full advantage of plasma and TIG welding processes. The two arcs of plasma and TIG were pulled into each other into one coupled arc under the effect of Lorentz force and plasma flow force during welding experiments. The arc behavior of coupled arc was studied by means of its arc profile, arc pressure and arc force conditions. The coupled arc pressure distribution measurements were performed. The effects of welding conditions on coupled arc pressure were evaluated and the maximum coupled arc pressure was improved compared with single-plasma arc and single-TIG arc. It was found that the maximum arc pressure was mainly determined by plasma arc current and plasma gas flow. Compared with traditional hybrid welding method, the efficiency was obviously higher and the welding heat-input was lower. The epitaxial solidification of the weld was inhibited, the tensile strength of the welded joints was higher. According to the results, the proposed coupled arc welding process has both advantages of plasma arc and TIG method, and it has a broad application prospect. Full article
(This article belongs to the Special Issue Science, Characterization and Technology of Joining and Welding)
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7 pages, 1635 KiB  
Article
Comparasion of Impact and Tensile Properties of High-Strength Steel
by Željko Alar and Davor Mandić *
Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000 Zagreb, Croatia
Metals 2018, 8(7), 511; https://doi.org/10.3390/met8070511 - 3 Jul 2018
Cited by 6 | Viewed by 6491
Abstract
Tensile and impact properties of API 5L X80 steel were investigated and compared in order to evaluate their relation. Yield and maximum forces under dynamic impact testing were obtained from force-displacement curves. Dynamic yield strength was estimated using the von Mises yield criterion. [...] Read more.
Tensile and impact properties of API 5L X80 steel were investigated and compared in order to evaluate their relation. Yield and maximum forces under dynamic impact testing were obtained from force-displacement curves. Dynamic yield strength was estimated using the von Mises yield criterion. A different approach was taken in order to estimate the dynamic tensile strength; the instrumented RKP 450 Zwick/Roell machine was used for this specific purpose. From the 10-mm-thick steel plate, Charpy V notch (CVN) samples were cut off in longitudinal orientation considering the rolling direction. For this research, CVN specimens were machined according to the ISO 148:2016 standard. Tensile specimens were machined according to the ISO 6892-1:2016 standard. It was found that the results between the tensile and impact properties were very close and within 5%. Full article
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15 pages, 5038 KiB  
Article
Weld Seam Geometry and Electrical Resistance of Laser-Welded, Aluminum-Copper Dissimilar Joints Produced with Spatial Beam Oscillation
by Michael Jarwitz *, Florian Fetzer, Rudolf Weber and Thomas Graf
Institut fuer Strahlwerkzeuge (IFSW), Pfaffenwaldring 43, 70569 Stuttgart, Germany
Metals 2018, 8(7), 510; https://doi.org/10.3390/met8070510 - 3 Jul 2018
Cited by 43 | Viewed by 8379
Abstract
Spatial beam oscillation during laser beam welding of aluminum to copper was investigated. The beam was spatially oscillated perpendicular to the direction of feed in a sinusoidal mode. The influence of the oscillation amplitude and frequency on the weld seam geometry and the [...] Read more.
Spatial beam oscillation during laser beam welding of aluminum to copper was investigated. The beam was spatially oscillated perpendicular to the direction of feed in a sinusoidal mode. The influence of the oscillation amplitude and frequency on the weld seam geometry and the implications on the electrical resistance of the joints was investigated. It was found that spatial beam oscillation allows to set the welding depth and seam width virtually independent of each other. Furthermore, low welding depths into the lower copper sheet in combination with high ratios of seam width at the interface of the two sheets to welding depth into the lower copper sheet result in low electrical resistances of the welds. Low electrical resistances were found to correlate with high mechanical strengths of the welds. Full article
(This article belongs to the Special Issue Dissimilar Metal Welding)
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20 pages, 21062 KiB  
Article
Experimental Study of Surface Characteristic in Electrochemical Machining of 35CrMo Steel
by Hang Zhang, Shuhai Liu *, Weichao Yue, Huaping Xiao and Peng Zhang
College of Mechanical and Transportation Engineering, China University of Petroleum-Beijing, Beijing 102249, China
Metals 2018, 8(7), 509; https://doi.org/10.3390/met8070509 - 3 Jul 2018
Cited by 11 | Viewed by 4037
Abstract
35CrMo steel is a widely used material in machinery equipment for the petroleum industry. With the improvement of exploring technology, some particular complex features cannot be achieved with traditional processing methods. However, electrochemical machining provides a potential solution to such problems, especially in [...] Read more.
35CrMo steel is a widely used material in machinery equipment for the petroleum industry. With the improvement of exploring technology, some particular complex features cannot be achieved with traditional processing methods. However, electrochemical machining provides a potential solution to such problems, especially in the machining of the turbine blades of turbine drilling tools, in which the surface behavior of the workpiece is an important basis for judging the machining effect. To investigate the surface behavior of 35CrMo after electrochemical machining, the electrochemical machining experiment of 35CrMo steel was conducted by a self-made experimental system. Effects of the electrolyte type, concentration, and current density on surface quality were investigated in this study. The surface characteristics of 35CrMo steel were analyzed under different current densities in three different electrolytes—NaCl, NaClO3 and NaNO3—with different concentrations. Based on the obtained results, an optimum machining plan was obtained. The principle of the electrolysis reaction of 35CrMo steel in NaCl, NaClO3 and NaNO3 electrolytes were studied as well. Experimental results showed that the best surface quality of 35CrMo steel was achieved under an NaClO3 electrolyte concentration of 200 g/L and current density of 30 A/cm2. The results in this paper provide a theoretical basis for the effective machining of complex parts such as downhole turbine blades. Full article
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15 pages, 3956 KiB  
Article
Correlation between the Liquid Fraction, Microstructure and Tensile Behaviors of 7075 Aluminum Alloy Processed by Recrystallization and Partial Remelting (RAP)
by Jinlong Fu †, Dong Yang † and Kaikun Wang *
1 School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
† These authors contributed equally to this work.
Metals 2018, 8(7), 508; https://doi.org/10.3390/met8070508 - 2 Jul 2018
Cited by 10 | Viewed by 4120
Abstract
The recrystallization and partial remelting (RAP) method was applied to obtain the semisolid 7075 aluminum alloy with different liquid fractions. The effects of liquid fraction on the microstructure and tensile properties were determined in detail. The results show that during the semisolid isothermal [...] Read more.
The recrystallization and partial remelting (RAP) method was applied to obtain the semisolid 7075 aluminum alloy with different liquid fractions. The effects of liquid fraction on the microstructure and tensile properties were determined in detail. The results show that during the semisolid isothermal treatment, the number of the intra-granular liquid droplets increased initially with the melting of the eutectic phases. Extension of isothermal soaking led to the coarsening and spheroidization of the intra-granular droplets. Finally, these liquid droplets merged and moved towards the grain exterior. The room temperature tensile strength of the RAP-processed AA7075 alloy, which were isothermally soaked at 600 and 610 °C, increased with the holding time from 5 to 15 min and then decreased dramatically from 15 to 25 min, whilst that soaked at 620 °C decreased monotonously. The fracture morphology exhibited intra-granular fracture mode at low liquid fractions. However, it transformed to a completely brittle and inter-granular type at high liquid fractions and the cohesive force of the liquid-solid interfaces at the grain boundaries determined the strength of the alloys. The transfer of the intra-granular liquid droplets into the inter-granular liquid phase played a significant role for the different fracture behaviors of the RAP-processed AA7075 alloy. The paper provides some reference for better controlling the microstructure and mechanical properties in semisolid processing. Full article
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11 pages, 4884 KiB  
Article
Effect of Tempering Temperatures on Tensile Properties and Rotary Bending Fatigue Behaviors of 17Cr2Ni2MoVNb Steel
by Sheng-Guan Qu *, Ya-Long Zhang, Fu-Qiang Lai and Xiao-Qiang Li
School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China
Metals 2018, 8(7), 507; https://doi.org/10.3390/met8070507 - 2 Jul 2018
Cited by 15 | Viewed by 3680
Abstract
With the rapid development of the automotive industry in China, the common gear steels no longer meet the high speed and heavy load requirements of the automotive industry. 17Cr2Ni2MoVNb steel is a new type of gear steel in the automotive industry, but the [...] Read more.
With the rapid development of the automotive industry in China, the common gear steels no longer meet the high speed and heavy load requirements of the automotive industry. 17Cr2Ni2MoVNb steel is a new type of gear steel in the automotive industry, but the mechanical properties of 17Cr2Ni2MoVNb are not well documented. In this study, the tensile properties and rotary bending fatigue behaviors of 17Cr2Ni2MoVNb were investigated, (quenched at 860 °C and tempered at 180, 400, 620 °C); the microstructures and fracture surface were analyzed using an optical microscope, scanning electron microscopy and transmission electron microscopy. The results show that at higher tempering temperatures, the tissue was denser, and the residual austenite transformed into lower bainite or tempered martensite. Dislocation density reduced while tempering temperature increased. Moreover, the samples with a tempering temperature of 180 °C exhibited the highest tensile strength of 1456 MPa, in addition to fatigue limits of 730, 700 and 600 MPa at temperatures of 180, 400, and 620 °C, respectively. Full article
(This article belongs to the Special Issue Fatigue and Wear for Steels)
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41 pages, 8475 KiB  
Review
A Review of Metastable Beta Titanium Alloys
by R. Prakash Kolli 1,* and Arun Devaraj 2
1 Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
2 Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99354, USA
Metals 2018, 8(7), 506; https://doi.org/10.3390/met8070506 - 30 Jun 2018
Cited by 548 | Viewed by 42470
Abstract
In this article, we provide a broad and extensive review of beta titanium alloys. Beta titanium alloys are an important class of alloys that have found use in demanding applications such as aircraft structures and engines, and orthopedic and orthodontic implants. Their high [...] Read more.
In this article, we provide a broad and extensive review of beta titanium alloys. Beta titanium alloys are an important class of alloys that have found use in demanding applications such as aircraft structures and engines, and orthopedic and orthodontic implants. Their high strength, good corrosion resistance, excellent biocompatibility, and ease of fabrication provide significant advantages compared to other high performance alloys. The body-centered cubic (bcc) β-phase is metastable at temperatures below the beta transus temperature, providing these alloys with a wide range of microstructures and mechanical properties through processing and heat treatment. One attribute important for biomedical applications is the ability to adjust the modulus of elasticity through alloying and altering phase volume fractions. Furthermore, since these alloys are metastable, they experience stress-induced transformations in response to deformation. The attributes of these alloys make them the subject of many recent studies. In addition, researchers are pursuing development of new metastable and near-beta Ti alloys for advanced applications. In this article, we review several important topics of these alloys including phase stability, development history, thermo-mechanical processing and heat treatment, and stress-induced transformations. In addition, we address recent developments in new alloys, phase stability, superelasticity, and additive manufacturing. Full article
(This article belongs to the Special Issue Deformation-Induced Phase Transformations in Steels and Non-Ferrous Alloys)
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21 pages, 10424 KiB  
Article
Fatigue Response of As-Built DMLS Maraging Steel and Effects of Aging, Machining, and Peening Treatments
by Dario Croccolo 1, Massimiliano De Agostinis 1, Stefano Fini 1, Giorgio Olmi 1,*, Francesco Robusto 1, Snežana Ćirić Kostić 2, Aleksandar Vranić 2 and Nebojša Bogojević 2
1 Department of Industrial Engineering (DIN), University of Bologna, 40136 Bologna, Italy
2 Faculty of Mechanical and Civil Engineering in Kraljevo, University of Kragujevac, Kraljevo 36000, Serbia
Metals 2018, 8(7), 505; https://doi.org/10.3390/met8070505 - 29 Jun 2018
Cited by 47 | Viewed by 6377
Abstract
The main motivations for this study arise from the need for an assessment of the fatigue performance of DMLS-produced Maraging Steel MS1, when it is used in the “as fabricated” state. The literature indicates a lack of knowledge from this point of view; [...] Read more.
The main motivations for this study arise from the need for an assessment of the fatigue performance of DMLS-produced Maraging Steel MS1, when it is used in the “as fabricated” state. The literature indicates a lack of knowledge from this point of view; moreover, the great potentials of the additive process may be more and more incremented, if an easier and cheaper procedure could be used after the building stage. The topic has been tackled experimentally, investigating the impact of heat treatment, machining, and micro-shot-peening on the fatigue strength with respect to the “as built state”. The results indicate that heat treatment may improve the fatigue response, as an effect of the relaxation of the process-induced tensile residual stresses. Machining can also be effective, but it must be followed (not preceded) by shot-peening, to benefit from the compressive residual stress state generated by the latter. Moreover, heat treatment and machining are related by a strong positive interaction, meaning their effects are synergistically magnified when they are applied together. The experimental study has been completed by fractographic as well as micrographic analyses, investigating the impact of the heat treatment on the actual microstructure induced by the stacking process. Full article
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