Microstructure and Properties of Intermetallics

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 5488

Special Issue Editors

Department of Materials Science and Engineering, Guangdong Technion Israel Institute of Technology, Shantou 515063, China
Interests: characterization; intermetallics; interface; films
Department of Mechanics, College of Engineering, Lishui University, Lishui 323000, China
Interests: microstructure and mechanical properties of TiAl alloy; powder metallurgy; ingot metallurgy method

Special Issue Information

Dear Colleagues,

Intermetallic compounds can exhibit many excellent properties vastly different from those of pure metals or their alloys—for example, high melting points; high thermal conductivity; low densities; great strength; good oxidation resistance; low ductility; and brittle fracture at room temperature. Moreover, intermetallics possess strong stability at high temperatures. Therefore, they can compete with and surpass conventional metallic materials in highly demanding structural applications in such key fields as the automotive, aeronautic, energy, and transport sectors.

A deeper and more fundamental understanding of the microstructure evolution mechanism would accelerate the improvement of mechanical properties and processibility of intermetallics. Research development of such alloys over the years primarily focused on the refinement of the microstructure and improvement of properties through compositional optimizations and the application of various processing technologies.

The main groups into which intermetallics can be classified are: nickel aluminides, iron aluminides, titanium aluminides and others such as silicides, nickel titanium, and refractory metal aluminides.

The aim of this Special Issue is to present a review of the latest advances in the various aspects of microstructure and the various properties of intermetallics. We welcome contributions on topics that include, but are not limited to:

  • Intermetallics
  • structure characterization
  • Additive Manufacturing
  • Phase transformation
  • stability and ductility
  • Heat treatment
  • corrosion and oxidation
  • Strengthen

Dr. Limei Cha
Dr. Yongjun Su
Guest Editors

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Keywords

  • intermetallics
  • interface
  • surface
  • boundary
  • structural characterization
  • mechanical properties

Published Papers (5 papers)

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Research

11 pages, 2164 KiB  
Article
Evaluation of Forged TiAl Alloy Usefulness Based on Their Impact Resistance
by Toshimitsu Tetsui
Metals 2023, 13(12), 1991; https://doi.org/10.3390/met13121991 - 08 Dec 2023
Cited by 1 | Viewed by 716
Abstract
The purpose of this study is to determine if forged TiAl alloys are worth using for small parts such as jet engine turbine blades. As part of this goal, this study investigated ways to improve the impact resistance of forged TiAl alloys and [...] Read more.
The purpose of this study is to determine if forged TiAl alloys are worth using for small parts such as jet engine turbine blades. As part of this goal, this study investigated ways to improve the impact resistance of forged TiAl alloys and compared them to cast TiAl alloys. The effects of additive elements and microstructure on the impact resistance of forged ternary TiAl alloys of 43.5 at. % Al were evaluated using the Charpy impact test on specimens heated to 500 °C prior to testing. The impact resistance of the forged alloys improved with the addition of Cr, V, and Mn and deteriorated with the addition of Nb. The impact resistance of the microstructure containing a β-phase, a common microstructure in forged TiAl alloys, was significantly lower. The fully lamellar structure obtained at the expense of forgeability showed much higher impact resistance than this. However, even the best impact resistance of the forged alloys was significantly inferior to that of cast ternary alloys of 46.5 at. % Al prepared with the same additive content. Combined with the high cost and low high-temperature strength of the forged TiAl alloys, it is concluded that it is pointless to use forged TiAl alloys for small parts that can be made via casting. Full article
(This article belongs to the Special Issue Microstructure and Properties of Intermetallics)
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12 pages, 2060 KiB  
Article
Structure and Properties of TiNi Shape Memory Alloy after Quasi-Continuous Equal-Channel Angular Pressing in Various Aged States
by Roman Karelin, Victor Komarov, Vladimir Cherkasov, Irina Khmelevskaya, Vladimir Andreev, Vladimir Yusupov and Sergey Prokoshkin
Metals 2023, 13(11), 1829; https://doi.org/10.3390/met13111829 - 30 Oct 2023
Viewed by 1571
Abstract
The effect of quasi-continuous (QC) equal-channel angular pressing (ECAP) in various pre-aged states on the structure formation and mechanical and functional properties of a hyper-equiatomic titanium nickelide (TiNi) shape memory alloy is studied. QC ECAP with a channel intersection angle of 110° is [...] Read more.
The effect of quasi-continuous (QC) equal-channel angular pressing (ECAP) in various pre-aged states on the structure formation and mechanical and functional properties of a hyper-equiatomic titanium nickelide (TiNi) shape memory alloy is studied. QC ECAP with a channel intersection angle of 110° is carried out at a temperature of 450 °C after aging for 1 and 5 h for three passes. To investigate the obtained structure and properties, the following research methods are applied: transmission electron microscopy, XRD analysis, calorimetric study, tension and hardness tests, and a special technique for the determination of functional properties. QC ECAP allows for the considerable refinement of structural elements and results in obtaining a mixed fine-grade structure, with structural elements of average sizes of 92 nm after pre-aging for 1 h and 115 nm after pre-aging for 5 h. Pre-aging for 5 h before QC ECAP, in combination with QC ECAP and post-deformation aging at 430 °C for 1 h, provides the best combination of mechanical and functional properties: a dislocation yield stress of 1410 MPa, ultimate tensile strength of 1562 MPa, and total recoverable strain of 11.6%. These values are comparable with the best results obtained for titanium nickelide and expand opportunities for the application of smart shape memory devices. Full article
(This article belongs to the Special Issue Microstructure and Properties of Intermetallics)
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20 pages, 17781 KiB  
Article
Improving Forging Outcomes of Cast Titanium Aluminide Alloy via Cyclic Induction Heat Treatment
by Sean Peters, Aurik Andreu, Marcos Perez and Paul Blackwell
Metals 2023, 13(8), 1420; https://doi.org/10.3390/met13081420 - 08 Aug 2023
Viewed by 934
Abstract
The objective of this research was to improve the forging outcome of peritectic solidifying cast titanium aluminide (TiAl) 4822 alloy (Ti-48Al-2Nb-2Cr at.%) in hot isostatic pressed and homogenised (HH) condition using cyclic induction heat treatment (CHT). This study adds to research around CHT [...] Read more.
The objective of this research was to improve the forging outcome of peritectic solidifying cast titanium aluminide (TiAl) 4822 alloy (Ti-48Al-2Nb-2Cr at.%) in hot isostatic pressed and homogenised (HH) condition using cyclic induction heat treatment (CHT). This study adds to research around CHT for TiAl alloys by applying industrially relevant induction heating to conduct five heating cycles at the single αphase temperatures (1370 °C) necessary for grain refinement. Two cooling rates were explored in each cycle, air cooling (ACCHT) and controlled furnace-like cooling (FCCHT), without returning to room temperature. Samples were assessed at each stage in terms of their morphologies, lamellar grain size and content, as well as phase and dynamic recrystallised fraction, and subsequent primary and secondary compression behaviour with uniaxial isothermal compression. The FCCHT process resulted in a homogeneously refined fully lamellar microstructure, and ACCHT, in a heterogeneous microstructure consisting of lamellar and feathery γ (γf) at differing fractions across the piece, depending on the cooling rate compared with HH. The results show that CHT improved forging outcomes for both compression stages investigated, resulting in uniform compression samples with higher volumes of dynamic recrystallised material compared with the instability seen with the compression of HH material. Full article
(This article belongs to the Special Issue Microstructure and Properties of Intermetallics)
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9 pages, 1228 KiB  
Communication
Effect of Severe Torsion Deformation on Structure and Properties of Titanium–Nickel Shape Memory Alloy
by Victor Komarov, Roman Karelin, Vladimir Cherkasov, Vladimir Yusupov, Grzegorz Korpala, Rudolf Kawalla, Ulrich Prahl and Sergey Prokoshkin
Metals 2023, 13(6), 1099; https://doi.org/10.3390/met13061099 - 10 Jun 2023
Cited by 2 | Viewed by 897
Abstract
In the present work, the possibility of applying severe torsion deformation (STD) to a bulk near-equiatomic NiTi shape memory alloy in order to accumulate super-high strain and improve mechanical and functional properties was studied. STD was performed using the multidirectional test system “BÄHR [...] Read more.
In the present work, the possibility of applying severe torsion deformation (STD) to a bulk near-equiatomic NiTi shape memory alloy in order to accumulate super-high strain and improve mechanical and functional properties was studied. STD was performed using the multidirectional test system “BÄHR MDS-830” at a temperature of 500 °C (the upper border temperature for the development of dynamic polygonization) in 14 and 30 turns with accumulated true strain values of 4.3 and 9.1, respectively. Structural phase state and properties were studied using differential scanning calorimetry, X-ray diffractometry, transmission electron microscopy, hardness measurements, and thermomechanical bending tests. STD at 500 °C allowed for the accumulation of high strain without failure. As a result of STD in 30 turns, a submicrocrystalline structure with an average grain/subgrain size of about 500 nm was formed. This structure ensured the achievement of high maximum completely recoverable strain values of 6.1–6.8%. The results obtained show the prospects of applying severe torsion straining deformation to titanium nickelide in terms of forming an ultrafine-grained structure and high properties. Full article
(This article belongs to the Special Issue Microstructure and Properties of Intermetallics)
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15 pages, 29528 KiB  
Article
Effect of Heat Treatment on the Microstructure and Mechanical Properties of a Ti-TiAl Laminate Composite
by Wei Sun, Ning Cui, Yongjun Su, Shuling Zhang, Tiewei Xu, Xiaopeng Wang and Fantao Kong
Metals 2023, 13(4), 708; https://doi.org/10.3390/met13040708 - 04 Apr 2023
Viewed by 984
Abstract
The effect of an innovative two-step heat-treatment process on the microstructure and mechanical properties of a Ti-TiAl laminate composite fabricated by hot-pack rolling was studied in this paper. After heat treatment, the fracture toughness of the composite was enhanced and the elongation of [...] Read more.
The effect of an innovative two-step heat-treatment process on the microstructure and mechanical properties of a Ti-TiAl laminate composite fabricated by hot-pack rolling was studied in this paper. After heat treatment, the fracture toughness of the composite was enhanced and the elongation of the composite was almost twice that of the initial one. These changes were due to the dislocations and substructures stored in the Ti-43Al-9V alloy being decreased, the microstructure of the DsTi700 alloy turning to a duplex structure, the acicular α2 phase being precipitated at the interfacial region and the residual stresses stored in interfacial region being eliminated. The precipitation of dual-scale silicides was the main reason for the slightly reduced strength. Compared with the initial composite, the tensile strength of the heat-treated composite at 25° and 700° only reduced by 2.7% and 4%, respectively. The primary annealing temperature had a huge impact on the mechanical properties of the composite. However, with the change in secondary annealing temperature, the mechanical properties of the composite were not changed significantly. After heat treatment at 940–960 °C/2 h/AC + 725–750 °C/6 h/AC, the composite might possess high, comprehensive mechanical properties. Full article
(This article belongs to the Special Issue Microstructure and Properties of Intermetallics)
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