Special Issue "Intermetallics 2016"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (30 June 2016)

Special Issue Editor

Guest Editor
Dr. Ana Sofia Ramos

CEMUC®, Department of Mechanical Engineering, University of Coimbra, R.Luís Reis Santos, 3030-788 Coimbra, Portugal
E-Mail
Interests: Nanomaterials; Reactive materials; Titanium and nickel aluminides; Shape memory alloys; Reactive multilayer thin films; Phase transformations; In situ studies using synchrotron radiation; Micromanufacturing; Joining; Self-healing in metallic alloys

Special Issue Information

Dear Colleagues,

The combination of low density, high strength, and good corrosion resistance makes intermetallics promising for structural applications, especially at high temperatures and in severe environments. Intermetallic compounds can be produced from metals that exothermically react with each other, releasing energy that is useful for several applications, including joining. Furthermore, these materials also have potential for functional applications since some intermetallic phases have unique properties, such as shape memory or thermo electric effect. Intermetallic phases of interest include aluminides, silicides, Laves and Heusler phases, among others. As a result of the increasing demand for novel/advanced materials with improved properties, recent years have been marked by the return of intermetallics.

This Special Issue will cover recent progress and new developments regarding all aspects of intermetallic-based materials, including processing, joining, modeling, characterization, testing, and application. From the application perspective, contributions related to intermetallic-based materials intended for structural, as well as for functional, applications are welcome.

Papers focusing on innovative theoretical or experimental approaches to understand the complex relationship between structure, property, and functionality of intermetallic materials or multiphase alloys, where intermetallic compounds are the major constituents, are invited for inclusion in this Special Issue.

Dr. A. S. Ramos
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

 

Keywords

  • ŸSelf-propagating high-temperature synthesis
  • ŸShape memory alloys
  • ŸIntermetallic composites
  • ŸReactive materials
  • ŸModeling and numerical simulations
  • ŸPhase transformations
  • ŸDefects and diffusion mechanisms
  • ŸEnvironmental effects, including oxidation and corrosion
  • ŸMechanical properties
  • ŸFracture and crack growth
  • Medical applications
  • ŸEnergy storage applications
  • ŸNovel structural and functional applications
  • Joining

Published Papers (18 papers)

View options order results:
result details:
Displaying articles 1-18
Export citation of selected articles as:

Editorial

Jump to: Research

Open AccessEditorial Intermetallics
Metals 2017, 7(10), 446; doi:10.3390/met7100446
Received: 10 October 2017 / Revised: 17 October 2017 / Accepted: 18 October 2017 / Published: 20 October 2017
PDF Full-text (165 KB) | HTML Full-text | XML Full-text
Abstract
The combination of low density, high strength, and good corrosion resistance makes intermetallics promising for structural applications, especially at high temperatures and under severe environments [...] Full article
(This article belongs to the Special Issue Intermetallics 2016)

Research

Jump to: Editorial

Open AccessFeature PaperArticle Tribocorrosion Study of Ordinary and Laser-Melted Ti6Al4V Alloy
Metals 2016, 6(10), 253; doi:10.3390/met6100253
Received: 7 August 2016 / Revised: 13 October 2016 / Accepted: 18 October 2016 / Published: 24 October 2016
Cited by 1 | PDF Full-text (8617 KB) | HTML Full-text | XML Full-text
Abstract
Titanium alloys are used in biomedical implants, as well as in other applications, due to the excellent combination of corrosion resistance and mechanical properties. However, the tribocorrosion resistance of titanium alloy is normally not satisfactory. Therefore, surface modification is a way to improve
[...] Read more.
Titanium alloys are used in biomedical implants, as well as in other applications, due to the excellent combination of corrosion resistance and mechanical properties. However, the tribocorrosion resistance of titanium alloy is normally not satisfactory. Therefore, surface modification is a way to improve this specific performance. In the present paper, laser surface-modified samples were tested in corrosion and pin-on-disk tribocorrosion testing in 0.90% NaCl under an average Hertzian pressure of 410 MPa against an alumina sphere. Laser-modified samples of Ti6Al4V were compared with ordinary Ti6Al4V alloy. Electrochemical impedance showed higher modulus for laser-treated samples than for ordinary Ti6Al4V ones. Moreover, atomic force microscopy revealed that laser-treated surfaces presented less wear than ordinary alloy for the initial exposure. For a further exposure to wear, i.e., when the wear depth is beyond the initial laser-affected layer, both materials showed similar corrosion behavior. Microstructure analysis and finite element method simulations revealed that the different behavior between the initial and the extensive rubbing was related to a fine martensite-rich external layer developed on the irradiated surface of the fusion zone. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Figure 1

Open AccessArticle Effect of Welding Parameters on Microstructure and Mechanical Properties of Cast Fe-40Al Alloy
Metals 2016, 6(10), 229; doi:10.3390/met6100229
Received: 27 June 2016 / Revised: 8 September 2016 / Accepted: 20 September 2016 / Published: 23 September 2016
PDF Full-text (3527 KB) | HTML Full-text | XML Full-text
Abstract
Friction welding of cast Fe-40Al alloy was carried out at 1000 rmp for various friction times, friction pressures, and forging pressures. The microstructures of the interface of welded samples were analyzed by optical and scanning electron microscopy (SEM). Micrographs demonstrated that excellent welding
[...] Read more.
Friction welding of cast Fe-40Al alloy was carried out at 1000 rmp for various friction times, friction pressures, and forging pressures. The microstructures of the interface of welded samples were analyzed by optical and scanning electron microscopy (SEM). Micrographs demonstrated that excellent welding formed continuously along the interface, except for samples welded for 3 s. Chemical compositions of the interface of the friction welded samples and of the fractured surface of all the specimens were determined using energy dispersive spectroscopy (EDS). After the welding process, shear tests were applied to the welded samples to determine the shear strength of joints. Test results indicated that the maximum shear strength was 469.5 MPa. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Figure 1

Open AccessArticle Utilization of a Porous Cu Interlayer for the Enhancement of Pb-Free Sn-3.0Ag-0.5Cu Solder Joint
Metals 2016, 6(9), 220; doi:10.3390/met6090220
Received: 29 June 2016 / Revised: 1 September 2016 / Accepted: 5 September 2016 / Published: 15 September 2016
PDF Full-text (5179 KB) | HTML Full-text | XML Full-text
Abstract
The joining of lead-free Sn-3.0Ag-0.5Cu (SAC305) solder alloy to metal substrate with the addition of a porous Cu interlayer was investigated. Two types of porous Cu interlayers, namely 15 ppi—pore per inch (P15) and 25 ppi (P25) were sandwiched in between SAC305/Cu substrate.
[...] Read more.
The joining of lead-free Sn-3.0Ag-0.5Cu (SAC305) solder alloy to metal substrate with the addition of a porous Cu interlayer was investigated. Two types of porous Cu interlayers, namely 15 ppi—pore per inch (P15) and 25 ppi (P25) were sandwiched in between SAC305/Cu substrate. The soldering process was carried out at soldering time of 60, 180, and 300 s at three temperature levels of 267, 287, and 307 °C. The joint strength was evaluated by tensile testing. The highest strength for solder joints with addition of P25 and P15 porous Cu was 51 MPa (at 180 s and 307 °C) and 54 MPa (at 300 s and 307 °C ), respectively. The fractography of the solder joint was analyzed by optical microscope (OM) and scanning electron microscopy (SEM). The results showed that the propagation of fracture during tensile tests for solder with a porous Cu interlayer occurred in three regions: (i) SAC305/Cu interface; (ii) inside SAC305 solder alloy; and (iii) inside porous Cu. Energy dispersive X-ray spectroscopy (EDX) was used to identify intermetallic phases. Cu6Sn5 phase with scallop-liked morphology was observed at the interface of the SAC305/Cu substrate. In contrast, the scallop-liked intermetallic phase together with more uniform but a less defined scallop-liked phase was observed at the interface of porous Cu and solder alloy. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Study of the Isothermal Oxidation Process and Phase Transformations in B2-(Ni,Pt)Al/RENE-N5 System
Metals 2016, 6(9), 208; doi:10.3390/met6090208
Received: 8 June 2016 / Revised: 26 July 2016 / Accepted: 20 August 2016 / Published: 1 September 2016
PDF Full-text (3264 KB) | HTML Full-text | XML Full-text
Abstract
Changes in composition, crystal structure and phase transformations of B2-(Ni,Pt)Al coatings upon isothermal oxidation experiments (natural and scale free oxidation) at 1100 °C, as a function of time beyond their martensitic transformation, are reported. Specifically, the analysis of lattice parameter and composition are
[...] Read more.
Changes in composition, crystal structure and phase transformations of B2-(Ni,Pt)Al coatings upon isothermal oxidation experiments (natural and scale free oxidation) at 1100 °C, as a function of time beyond their martensitic transformation, are reported. Specifically, the analysis of lattice parameter and composition are performed to identify changes in the B2-(Ni,Pt)Al phase upon the chemically-driven L10-(Ni,Pt)Al and L12-(Ni,Pt)3Al transformations. The B2-(Ni,Pt)Al phase was found to disorder and transform the martensite during the heat treatments for both oxidation experiments at approximately 36.3 and 40.9 at. % of Al, 47.7 and 42.9 at. % of Ni, 6.2 and 8.5 at. % of Pt, 4.2 and 2.9 at. % of Cr and 4.4 and 3.8 at. % of Co. The lattice constant and the long-range order parameter of the B2-(Ni,Pt)Al phase decreased linearly as a function of the elemental content irrespective of the nature of the oxidation experiments. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Devising Strain Hardening Models Using Kocks–Mecking Plots—A Comparison of Model Development for Titanium Aluminides and Case Hardening Steel
Metals 2016, 6(9), 204; doi:10.3390/met6090204
Received: 29 June 2016 / Revised: 4 August 2016 / Accepted: 22 August 2016 / Published: 29 August 2016
PDF Full-text (10902 KB) | HTML Full-text | XML Full-text
Abstract
The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a
[...] Read more.
The present study focuses on the development of strain hardening models taking into account the peculiarities of titanium aluminides. In comparison to steels, whose behavior has been studied extensively in the past, titanium aluminides possess a much larger initial work hardening rate, a sharp peak stress and pronounced softening. The work hardening behavior of a TNB-V4 (Ti–44.5Al–6.25Nb–0.8Mo–0.1B) alloy is studied using isothermal hot compression tests conducted on a Gleeble 3500 simulator, and compared to the typical case hardening steel 25MoCrS4. The behavior is analyzed with the help of the Kocks-Mecking plots. In contrast to steel the TNB-V4 alloy shows a non-linear course of θ (i.e., no stage-III hardening) initially and exhibits neither a plateau (stage IV hardening) nor an inflection point at all deformation conditions. The present paper describes the development and application of a methodology for the design of strain hardening models for the TNB-V4 alloy and the 25CrMoS4 steel by taking the course of the Kocks-Mecking plots into account. Both models use different approaches for the hardening and softening mechanisms and accurately predict the flow stress over a wide range of deformation conditions. The methodology may hence assist in further developments of more sophisticated physically-based strain hardening models for TiAl-alloys. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Gas-Solid Reaction Route toward the Production of Intermetallics from Their Corresponding Oxide Mixtures
Metals 2016, 6(8), 190; doi:10.3390/met6080190
Received: 29 June 2016 / Revised: 3 August 2016 / Accepted: 10 August 2016 / Published: 17 August 2016
Cited by 1 | PDF Full-text (8223 KB) | HTML Full-text | XML Full-text
Abstract
Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the “Reduction-Sintering” process. This methodology can
[...] Read more.
Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the “Reduction-Sintering” process. This methodology can be especially effective in producing components containing refractory metals. Additionally, in situ production of metallic powder from complex oxides containing more than one metallic element may result in in situ alloying during reduction, possibly at lower temperatures. With this motivation, in situ reduction of complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction route but also study the reaction kinetics and mechanism. Environmentally friendly gases like H2, CH4 and N2 were used for simultaneous reduction, carburization and nitridation, respectively. Different techniques have been utilized. A thermogravimetric analyzer was used to accurately control the process conditions and obtain reaction kinetics. The fluidized bed technique has been utilized to study the possibility of bulk production of intermetallics compared to milligrams in TGA. Carburization and nitridation of nascent formed intermetallics were successfully carried out. A novel method based on material thermal property was explored to track the reaction progress and estimate the reaction kinetics. This method implies the dynamic measure of thermal diffusivity using laser flash method. These efforts end up with a successful preparation of nanograined intermetallics like Fe-Mo and Ni-W. In addition, it ends up with simultaneous reduction and synthesis of Ni-WN and Ni-WC from their oxide mixtures in single step. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Influence of the Overlapping Factor and Welding Speed on T-Joint Welding of Ti6Al4V and Inconel 600 Using Low-Power Fiber Laser
Metals 2016, 6(6), 134; doi:10.3390/met6060134
Received: 18 February 2016 / Revised: 8 April 2016 / Accepted: 12 April 2016 / Published: 2 June 2016
Cited by 5 | PDF Full-text (5028 KB) | HTML Full-text | XML Full-text
Abstract
Double-sided laser beam welding of skin-stringer joints is an established method for many applications. However, in certain cases with limited accessibility, single-sided laser beam joining is considered. In the present study, single-sided welding of titanium alloy Ti6Al4V and nickel-based
[...] Read more.
Double-sided laser beam welding of skin-stringer joints is an established method for many applications. However, in certain cases with limited accessibility, single-sided laser beam joining is considered. In the present study, single-sided welding of titanium alloy Ti6Al4V and nickel-based alloy Inconel 600 in a T-joint configuration was carried out using continuous-wave (CW), low-power Ytterbium (Yb)-fiber laser. The influence of the overlapping factor and welding speed of the laser beam on weld morphology and properties was investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. XRD analysis revealed the presence of intermetallic layers containing NiTi and NiTi2 at the skin-stringer joint. The strength of the joints was evaluated using pull testing, while the hardness of the joints was analyzed using Vickers hardness measurement at the base metal (BM), fusion zone (FZ) and heat-affected zone (HAZ). The results showed that the highest force needed to break the samples apart was approximately 150 N at a laser welding power of 250 W, welding speed of 40 mm/s and overlapping factor of 50%. During low-power single-sided laser welding, the properties of the T-joints were affected by the overlapping factor and laser welding speed. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle The Effects of Al and Ti Additions on the Structural Stability, Mechanical and Electronic Properties of D8m-Structured Ta5Si3
Metals 2016, 6(6), 127; doi:10.3390/met6060127
Received: 6 January 2016 / Revised: 26 April 2016 / Accepted: 30 April 2016 / Published: 26 May 2016
Cited by 2 | PDF Full-text (3731 KB) | HTML Full-text | XML Full-text
Abstract
In the present study, the influence of substitutional elements (Ti and Al) on the structural stability, mechanical properties, electronic properties and Debye temperature of Ta5Si3 with a D8m structure were investigated by first principle calculations. The Ta5Si
[...] Read more.
In the present study, the influence of substitutional elements (Ti and Al) on the structural stability, mechanical properties, electronic properties and Debye temperature of Ta5Si3 with a D8m structure were investigated by first principle calculations. The Ta5Si3 alloyed with Ti and Al shows negative values of formation enthalpies, indicating that these compounds are energetically stable. Based on the values of formation enthalpies, Ti exhibits a preferential occupying the Ta4b site and Al has a strong site preference for the Si8h site. From the values of the bulk modulus (B), shear modulus (G) and Young’s modulus (E), we determined that both Ti and Al additions decrease both the shear deformation resistance and the elastic stiffness of D8m structured Ta5Si3. Using the shear modulus/bulk modulus ratio (G/B), Poisson’s ratio (υ) and Cauchy’s pressure, the effect of Ti and Al additions on the ductility of D8m-structured Ta5Si3 are explored. The results show that Ti and Al additions reduce the hardness, resulting in solid solution softening, but improve the ductility of D8m-structured Ta5Si3. The electronic calculations reveal that Ti and Al additions change hybridization between Ta-Si and Si-Si atoms for the binary D8m-structured Ta5Si3. The new Ta-Al bond is weaker than the Ta-Si covalent bonds, reducing the covalent property of bonding in D8m-structured Ta5Si3, while the new strong Ti4b-Ti4b anti-bonding enhances the metallic behavior of the binary D8m-structured Ta5Si3. The change in the nature of bonding can well explain the improved ductility of D8m-structured Ta5Si3 doped by Ti and Al. Moreover, the Debye temperatures, ΘD, of D8m-structured Ta5Si3 alloying with Ti and Al are decreased as compared to the binary Ta5Si3. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Enhanced Mechanical Properties of MgZnCa Bulk Metallic Glass Composites with Ti-Particle Dispersion
Metals 2016, 6(5), 116; doi:10.3390/met6050116
Received: 16 February 2016 / Revised: 4 May 2016 / Accepted: 10 May 2016 / Published: 17 May 2016
Cited by 3 | PDF Full-text (5070 KB) | HTML Full-text | XML Full-text
Abstract
Rod samples of Mg60Zn35Ca5 bulk metallic glass composites (BMGCs) dispersed with Ti particles have been successfully fabricated via injection casting. The glass forming ability (GFA) and the mechanical properties of these Mg-based BMGCs have been systematically investigated as
[...] Read more.
Rod samples of Mg60Zn35Ca5 bulk metallic glass composites (BMGCs) dispersed with Ti particles have been successfully fabricated via injection casting. The glass forming ability (GFA) and the mechanical properties of these Mg-based BMGCs have been systematically investigated as a function of the volume fraction (Vf) of Ti particles. The results showed that the compressive ductility increased with Vf. The mechanical performance of these BMGCs, with up to 5.4% compressive failure strain and 1187 MPa fracture strength at room temperature, can be obtained for the Mg-based BMGCs with 50 vol % Ti particles, suggesting that these dispersed Ti particles can absorb the energy of the crack propagations and can induce branches of the primary shear band into multiple secondary shear bands. It follows that further propagation of the shear band is blocked, enhancing the overall plasticity. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Open AccessFeature PaperArticle Joining of TiAl to Steel by Diffusion Bonding with Ni/Ti Reactive Multilayers
Metals 2016, 6(5), 96; doi:10.3390/met6050096
Received: 2 March 2016 / Revised: 14 April 2016 / Accepted: 20 April 2016 / Published: 25 April 2016
Cited by 3 | PDF Full-text (7130 KB) | HTML Full-text | XML Full-text
Abstract
Dissimilar diffusion bonds of TiAl alloy to AISI 310 stainless steel using Ni/Ti reactive multilayers were studied in this investigation. The Ni and Ti alternating layers were deposited by d.c. magnetron sputtering onto the base materials, with a bilayer thickness of 30 and
[...] Read more.
Dissimilar diffusion bonds of TiAl alloy to AISI 310 stainless steel using Ni/Ti reactive multilayers were studied in this investigation. The Ni and Ti alternating layers were deposited by d.c. magnetron sputtering onto the base materials, with a bilayer thickness of 30 and 60 nm. Joining experiments were performed at 700 and 800 °C for 60 min under pressures of 50 and 10 MPa. The effectiveness of using Ni/Ti multilayers to improve the bonding process was assessed by microstructural characterization of the interface and by mechanical tests. Diffusion bonded joints were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), high resolution TEM (HRTEM) and Fast Fourier transform (FFT). The bonding interfaces are thin (approximately 5 µm thick) with a layered microstructure. For all joints, the interface is mainly composed of equiaxed grains of NiTi and NiTi2. The thickness and number of layers depends on the joining conditions and bilayer thickness of the multilayers. Mechanical characterization of the joints was performed by nanoindentation and shear tests. Young´s modulus distribution maps highlight the phase differences across the joint´s interface. The highest shear strength value is obtained for the joint produced at 800 °C for 60 min under a pressure of 10 MPa using Ni/Ti multilayers with 30 nm of bilayer thickness. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Open AccessArticle Intermetallic Reactions during the Solid-Liquid Interdiffusion Bonding of Bi2Te2.55Se0.45 Thermoelectric Material with Cu Electrodes Using a Sn Interlayer
Metals 2016, 6(4), 92; doi:10.3390/met6040092
Received: 26 February 2016 / Revised: 13 April 2016 / Accepted: 19 April 2016 / Published: 22 April 2016
Cited by 1 | PDF Full-text (4463 KB) | HTML Full-text | XML Full-text
Abstract
The intermetallic compounds formed during the diffusion soldering of a Bi2Te2.55Se0.45 thermoelectric material with a Cu electrode are investigated. For this bonding process, Bi2Te2.55Se0.45 was pre-coated with a 1 μm Sn thin film
[...] Read more.
The intermetallic compounds formed during the diffusion soldering of a Bi2Te2.55Se0.45 thermoelectric material with a Cu electrode are investigated. For this bonding process, Bi2Te2.55Se0.45 was pre-coated with a 1 μm Sn thin film on the thermoelectric element and pre-heated at 250 °C for 3 min before being electroplated with a Ni barrier layer and a Ag reaction layer. The pre-treated thermoelectric element was bonded with a Ag-coated Cu electrode using a 4 μm Sn interlayer at temperatures between 250 and 325 °C. The results indicated that a multi-layer of Bi–Te–Se/Sn–Te–Se–Bi/Ni3Sn4 phases formed at the Bi2Te2.55Se0.45/Ni interface, ensuring sound cohesion between the Bi2Te2.55Se0.45 thermoelectric material and Ni barrier. The molten Sn interlayer reacted rapidly with both Ag reaction layers to form an Ag3Sn intermetallic layer until it was completely exhausted and the Ag/Sn/Ag sandwich transformed into a Ag/Ag3Sn/Ag joint. Satisfactory shear strengths ranging from 19.3 and 21.8 MPa were achieved in Bi2Te2.55Se0.45/Cu joints bonded at 250 to 300 °C for 5 to 30 min, dropping to values of about 11 MPa for 60 min, bonding at 275 and 300 °C. In addition, poor strengths of about 7 MPa resulted from bonding at a higher temperature of 325 °C for 5 to 60 min. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Open AccessArticle Structural Origin of the Enhanced Glass-Forming Ability Induced by Microalloying Y in the ZrCuAl Alloy
Metals 2016, 6(4), 67; doi:10.3390/met6040067
Received: 16 January 2016 / Revised: 16 March 2016 / Accepted: 17 March 2016 / Published: 23 March 2016
PDF Full-text (1927 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the structural origin of the enhanced glass-forming ability induced by microalloying Y in a ZrCuAl multicomponent system is studied by performing synchrotron radiation experiments combined with simulations. It is revealed that the addition of Y leads to the optimization of
[...] Read more.
In this work, the structural origin of the enhanced glass-forming ability induced by microalloying Y in a ZrCuAl multicomponent system is studied by performing synchrotron radiation experiments combined with simulations. It is revealed that the addition of Y leads to the optimization of local structures, including: (1) more Zr-centered and Y-centered icosahedral-like clusters occur in the microstructure; (2) the atomic packing efficiency inside clusters and the regularity of clusters are both enhanced. These structural optimizations help to stabilize the amorphous structure in the ZrCuAlY system, and lead to a high glass-forming ability (GFA). The present work provides an understanding of GFAs in multicomponent alloys and will shed light on the development of more metallic glasses with high GFAs. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Simulation and Experimental Investigation for the Homogeneity of Ti49.2Ni50.8 Alloy Processed by Equal Channel Angular Pressing
Metals 2016, 6(3), 45; doi:10.3390/met6030045
Received: 12 January 2016 / Revised: 2 February 2016 / Accepted: 15 February 2016 / Published: 25 February 2016
PDF Full-text (2232 KB) | HTML Full-text | XML Full-text
Abstract
Ti49.2Ni50.8 shape memory alloy (SMA) was processed by equal channel angular pressing (ECAP) for eight passes at 450 °C. The deformation homogeneity was analyzed on various planes across the thickness by Deform-3D software. Strain standard deviation (SSD) was used to
[...] Read more.
Ti49.2Ni50.8 shape memory alloy (SMA) was processed by equal channel angular pressing (ECAP) for eight passes at 450 °C. The deformation homogeneity was analyzed on various planes across the thickness by Deform-3D software. Strain standard deviation (SSD) was used to quantify deformation homogeneity. The simulation result shows that the strain homogeneity is optimized by the third pass. Deformation homogeneity of ECAP was analyzed experimentally using microhardness measurements. Experimental results show that the gradual evolution of hardness with increasing numbers of passes existed and the optimum homogeneity was achieved after three passes. This is in good agreement with simulation results. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Open AccessArticle Effect of Laser Surface Treatment on the Corrosion Behavior of FeCrAl-Coated TZM Alloy
Metals 2016, 6(2), 29; doi:10.3390/met6020029
Received: 6 December 2015 / Revised: 22 January 2016 / Accepted: 27 January 2016 / Published: 29 January 2016
Cited by 5 | PDF Full-text (1227 KB) | HTML Full-text | XML Full-text
Abstract
The current study involves the coating of Titanium-Zirconium-Molybdenum (TZM) alloy with FeCrAl through plasma thermal spraying which proved effective in improving the oxidation resistance of the substrate. A post-laser surface melting treatment further enhanced the surface protection of the TZM alloy. Oxidation tests
[...] Read more.
The current study involves the coating of Titanium-Zirconium-Molybdenum (TZM) alloy with FeCrAl through plasma thermal spraying which proved effective in improving the oxidation resistance of the substrate. A post-laser surface melting treatment further enhanced the surface protection of the TZM alloy. Oxidation tests conducted at 1100 °C in air indicated that some Mo oxides were formed at the surface but a relatively small amount of weight reduction was observed for FeCrAl-coated TZM alloys up to 60 min of treatment. The post-laser surface treatment following the plasma thermal spray process apparently delayed the severe oxidation process and surface spalling of the alloy. It was suggested that the slow reduction in weight in the post-laser-treated specimen was related to fewer defects in the coating layer. It was also found that a surface reaction layer formed through the diffusion of Fe into the Mo alloy substrate at high temperature. The layer mainly consisted of Fe-saturated Mo and FeMo intermetallic compounds. In order to observe the corrosion behavior of the laser-treated alloy in 3.5% NaCl solution, electrochemical characteristics were also investigated. A proposed equivalent circuit model for the specimen indicated localized corrosion of coated alloy with some permeable defects in the coating layer. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Open AccessArticle Modeling of TiAl Alloy Grating by Investment Casting
Metals 2015, 5(4), 2328-2339; doi:10.3390/met5042328
Received: 19 October 2015 / Revised: 3 December 2015 / Accepted: 4 December 2015 / Published: 9 December 2015
PDF Full-text (957 KB) | HTML Full-text | XML Full-text
Abstract
The investment casting of TiAl alloys has become the most promising cost-effective technique for manufacturing TiAl components. This study aimed to investigate a series of problems associated with the investment casting of TiAl alloys. The mold filling and solidification of this casting model
[...] Read more.
The investment casting of TiAl alloys has become the most promising cost-effective technique for manufacturing TiAl components. This study aimed to investigate a series of problems associated with the investment casting of TiAl alloys. The mold filling and solidification of this casting model were numerically simulated using ProCAST. Shrinkage porosity was quantitatively predicted by a built-in feeding criterion. The results obtained from the numerical simulations were compared with experiments, which were carried out on Vacuum Skull Furnace using an investment block mold. The investment casting of TiAl grating was conducted for verifying the correctness and feasibility of the proposed method. The tensile test results indicated that, at room temperature, the tensile strength and elongation were approximately 675 MPa and 1.7%, respectively. The microstructure and mechanical property of the investment cast TiAl alloy were discussed. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Open AccessArticle Effect of Ceramic Content on the Compression Properties of TiB2-Ti2AlC/TiAl Composites
Metals 2015, 5(4), 2200-2209; doi:10.3390/met5042200
Received: 29 September 2015 / Revised: 1 November 2015 / Accepted: 6 November 2015 / Published: 25 November 2015
Cited by 2 | PDF Full-text (737 KB) | HTML Full-text | XML Full-text
Abstract
In situ synthesized TiB2-reinforced TiAl composites usually possess high strength. However, it is very expensive to use B powder to synthesize TiB2 particles. Moreover, the strength enhancement of TiB2/TiAl composite is generally at the cost of plasticity. In
[...] Read more.
In situ synthesized TiB2-reinforced TiAl composites usually possess high strength. However, it is very expensive to use B powder to synthesize TiB2 particles. Moreover, the strength enhancement of TiB2/TiAl composite is generally at the cost of plasticity. In this study, in situ dual reinforcement TiB2-Ti2AlC/TiAl composites were fabricated by using B4C powder as the B and C source, which greatly reduces the potential production cost. The 6 vol. % TiB2-Ti2AlC/TiAl composite fabricated by using the Ti-Al-B4C system shows greatly improved compressive properties, i.e., 316 MPa and 234 MPa higher than those of TiAl alloy and with no sacrifice in plasticity. Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Open AccessArticle Experimental and Numerical Studies on Self-Propagating High-Temperature Synthesis of Ta5Si3 Intermetallics
Metals 2015, 5(3), 1580-1590; doi:10.3390/met5031580
Received: 11 August 2015 / Revised: 21 August 2015 / Accepted: 28 August 2015 / Published: 1 September 2015
Cited by 4 | PDF Full-text (1008 KB) | HTML Full-text | XML Full-text
Abstract
Formation of Ta5Si3 by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion
[...] Read more.
Formation of Ta5Si3 by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of Ta:Si = 5:3 was experimentally and numerically studied. Experimental evidence showed that the increase of either sample density or preheating temperature led to the increase of combustion wave velocity and reaction temperature. The apparent activation energy, Ea ≈ 108 kJ/mol, was determined for the synthesis reaction. Based upon numerical simulation, the Arrhenius factor of the rate function, K0 = 2.5 × 107 s−1, was obtained for the 5Ta + 3Si combustion system. In addition, the influence of sample density on combustion wave kinetics was correlated with the effective thermal conductivity (keff) of the powder compact. By adopting 0.005 ≤ keff/kbulk ≤ 0.016 in the computation model, the calculated combustion velocity and temperature were in good agreement with experimental data of the samples with compaction densities between 35% and 45% theoretical maximum density (TMD). Full article
(This article belongs to the Special Issue Intermetallics 2016)
Figures

Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Homogeneity challenges in SLM manufacturing of Ti-Al intermetallic
Author: Pavel Krakhmalev
Affiliation: Karlstad University, Sweden
Abstract: The investigation of intermetallic layers fabricated by selective laser melting (SLM) of mixtures of Al and Ti elemental powders was carried out to understand a correlation of microstructure, homogeneity and phase constitution with laser processing parameters. 
The results show challenges in manufacturing of homogeneous intermetallic material by means of SLM. The results revealed deviations in chemical composition of tracks compared to nominal mixture, phase constitution was also found different from equilibrium. The findings are discussed in relation to incomplete remixing of elements in the molten pool, possible evaporation of elements due to local melt overheating and rapid cooling preventing ordering processes. Opportunities to improve quality of intermetallic materials manufactured by SLM discussed in terms of optimization of laser parameters.

Title: Laser Welding of Open Cell Foams in Cuznal Shape Memory Alloy
Author: Carlo Biffi
Abstract: Cellular materials in shape memory alloys are very promising smart systems, able to combine functional properties of the material to lightness, stiffness and damping capacity of the cellular structure. The problem of their processing remains an open question with low modification of their properties. In this work the laser weldability of Cu73Zn21Al6 shape memory alloy in the form of open cell foams was studied. It was shown that the cellular structure can be successfully welded in lap joint configuration by using a thin plate of the same alloy. The geometrical characteristics of the joints was correlated to the process speed and the calorimetric properties were found not significantly affected by the laser process.

Title: Gas solid reaction rout toward the production of intermetallic from their corresponding oxide mixtures
Author: Hesham Ahmed, Ricardo Morales, Nurin Viswanathan and Seshadri Seetharaman
Abstract: Near-net shape forming of metallic components from metallic powders produced insitu from reduction of corresponding pure metal oxides has been not been explored to large extent. Such a process can be probably termed in short as “Reduction-Sintering” process. This methodology can be especially effective in producing components containing refractory metals. Additionally, insitu production of metallic powder from complex oxides containing more than one metallic element may result in insitu alloying during reduction, possibly at lower temperatures. With this motivation, In-situ reduction complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction rout but also study the reaction kinetics and mechanism..Friendly environmentally gases like H2, CH4 and N2 were used for simultaneous reduction,carbourizationand nitridation, respectively.
Different techniques have been utilized. Thermogravimetric analyzer to accurately controls the process conditions and reactions kinetics. Fluidized bed technique has been utilized to study the possibility of bulk production of intermetallics compared to milligrams in TGA. Carburization and nitridation of nascent formed intermetallics were successfully carried out. A novel method based on material thermal property was explored to track the reaction progress and estimate the reaction kinetics. This method implies the dynamic measure of thermal diffusivity using laser flash method.
These efforts end up with a successful preparation of nanograinedintermtalics like Fe-Mo and Ni-Wi. Also, it ends up with simultaneous reduction and synthesis of Ni-WN and Ni-WC from their oxide mixtures in single step. This novel method was further developed to produce intermetallic coatings on cupper surfaces.

Back to Top