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12 pages, 4184 KiB

Open AccessArticle

Martensitic Transformation Temperatures and Hall Effect in Ni_47−xMn_41+xIn₁₂ (x = 0, 1, 2) Alloys

by Vyacheslav V. Marchenkov, Sabina M. Emelyanova and Elena B. Marchenkova

Materials 2023, 16(2), 672; https://doi.org/10.3390/ma16020672 - 10 Jan 2023

Cited by 2 | Viewed by 1342

Abstract

At present, the question of the relationship between the characteristic martensitic transformation temperatures (MTT) and the electronic parameters of a system has not been fully studied. In the present work, an attempt to establish a similar relationship using the example of the concentration [...] Read more.

At present, the question of the relationship between the characteristic martensitic transformation temperatures (MTT) and the electronic parameters of a system has not been fully studied. In the present work, an attempt to establish a similar relationship using the example of the concentration of charge carriers, n, was made. The field dependences of Hall resistivity ρ_H and magnetization M of the magnetocaloric Ni_47−xMn_41+xIn₁₂ (x = 0, 1, 2) alloys were measured at T = 4.2 K and in magnetic fields of up to 80 kOe. The MTT were obtained from the temperature dependences of electrical resistivity and magnetization. It was observed that the MTT correlate strongly with both the valence electron concentration e/a and the electronic transport characteristics, which are the coefficient of the normal (NHE) R₀ and anomalous (AHE) R_S Hall effect and the concentration of charge carriers n. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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13 pages, 4447 KiB

Open AccessArticle

Crystallographic Features of Phase Transformations during the Continuous Cooling of a Ti6Al4V Alloy from the Single-Phase β-Region

by Inna A. Naschetnikova, Stepan I. Stepanov, Andrey A. Redikultsev, Valentin Yu. Yarkov, Maria A. Zorina and Mikhail L. Lobanov

Materials 2022, 15(17), 5840; https://doi.org/10.3390/ma15175840 - 24 Aug 2022

Cited by 3 | Viewed by 1458

Abstract

Crystallographic relationships between α- and β-phases resulting from phase transformations, which took place during the continuous water quenching (WQ), air cooling (AC) and furnace cooling (FC) of a Ti6Al4V plates solution treated at 1065 °C, were investigated by methods of electron backscatter diffraction [...] Read more.

Crystallographic relationships between α- and β-phases resulting from phase transformations, which took place during the continuous water quenching (WQ), air cooling (AC) and furnace cooling (FC) of a Ti6Al4V plates solution treated at 1065 °C, were investigated by methods of electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). WQ, AC and FC resulted in typical martensite, basket-weave and parallel-plate Widmanstatten structures, respectively. The experimental distribution of α/β-misorientations deviated from BOR at set discrete angles close to 22, 30, 35 and 43°. The experimental spectra of angles were confirmed by theoretical calculations of the possible misorientations between the α and β phases through the β_o→α→β_II –transformation path based on Burgers orientation relationship (BOR). Joint analysis of the experimental data and theoretical calculations revealed that the secondary β_II-phase was precipitated according to the sequence β_o→α→β_II during continuous cooling from the single-phase β-region. Similar spectra for α/β-phase misorientations for all investigated cooling rates acknowledged the similar transformation mechanisms and dominant shear component of the phase transformations. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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11 pages, 3916 KiB

Open AccessArticle

Kinetics of Ordering and Decomposition in Ti-Al-X (X = Si, Zr) Alloys: Monte Carlo Modeling

by Mikhail Petrik, Ilya Razumov, Yuri Gornostyrev, Inna Naschetnikova and Artemyi Popov

Materials 2022, 15(16), 5722; https://doi.org/10.3390/ma15165722 - 19 Aug 2022

Cited by 2 | Viewed by 1209

Abstract

To investigate the ordering and decomposition processes in Ti-Al-X [X = Si, Zr] alloys, the Monte Carlo simulations with first-principles parametrization of interatomic interactions were employed. It was shown that the processes of ordering and the precipitation in the Ti-Al system are closely [...] Read more.

To investigate the ordering and decomposition processes in Ti-Al-X [X = Si, Zr] alloys, the Monte Carlo simulations with first-principles parametrization of interatomic interactions were employed. It was shown that the processes of ordering and the precipitation in the Ti-Al system are closely related, and the stage of homogeneous ordering precedes the formation of ordered Ti₃Al particles. It was found that the duration of homogeneous ordering is very sensitive to the annealing temperature and composition of alloy, and that precipitation becomes preferable as the temperature rises. In particular, uniform ordering of alloy Ti-12 at % Al was found during long-term holding at temperature below 850 K, while annealing at 1000 K resulted in formation of ordered Ti₃Al particles. The obtained results agree well with the experimental data and allow explaining the features of the microstructure formed during annealing of the Ti-Al-X alloys. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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43 pages, 8120 KiB

Open AccessArticle

Multicomponent Aging Al-Li-Based Alloys of the Latest Generation: Structural and Phase Transformations, Treatments, Properties, and Future Prospects

by Dmitriy Y. Rasposienko, Larisa I. Kaigorodova, Vladimir G. Pushin and Yurii M. Ustugov

Materials 2022, 15(12), 4190; https://doi.org/10.3390/ma15124190 - 13 Jun 2022

Cited by 6 | Viewed by 1684

Abstract

An overview of modern material science problems is presented for ultralightweight high-modulus commercial Al-Li-based alloys in historical retrospect. Numerous particular examples of the Soviet and Russian aviation whose various designs were made of these alloys confirm their successful innovative potential. The key regularities [...] Read more.

An overview of modern material science problems is presented for ultralightweight high-modulus commercial Al-Li-based alloys in historical retrospect. Numerous particular examples of the Soviet and Russian aviation whose various designs were made of these alloys confirm their successful innovative potential. The key regularities of multicomponent alloying are discussed for the master alloys and modern commercial Al-Li-based alloys of the latest generation; the features typical of their microstructures, phase composition, and properties formed during aging are analyzed. The main mechanisms of phase formation are generalized for standard thermal and thermomechanical treatments. Recent original achievements have been obtained in designing of unique structural and phase transformations in these commercial alloys by means of methods of severe plastic deformations followed by heat treatment and storage. Using the example of three Russian commercial alloys of last generation, the basic principles of creating and controlling an ultrafine-grained structure, the origin and growth of stable nanophases of various types and chemical composition that determine the physicomechanical properties of alloys are established. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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23 pages, 11579 KiB

Open AccessArticle

Structural and Phase Transformations and Physical and Mechanical Properties of Cu-Al-Ni Shape Memory Alloys Subjected to Severe Plastic Deformation and Annealing

by Alexey E. Svirid, Vladimir G. Pushin, Natalia N. Kuranova, Vladimir V. Makarov and Yuri M. Ustyugov

Materials 2021, 14(16), 4394; https://doi.org/10.3390/ma14164394 - 5 Aug 2021

Cited by 9 | Viewed by 2646

Abstract

Using the methods of electron microscopy and X-ray analysis in combination with measurements of the electrical resistance and magnetic susceptibility, the authors have obtained data on the peculiar features of pre-martensitic states and martensitic transformations, as well as subsequent decomposition, in the alloys [...] Read more.

Using the methods of electron microscopy and X-ray analysis in combination with measurements of the electrical resistance and magnetic susceptibility, the authors have obtained data on the peculiar features of pre-martensitic states and martensitic transformations, as well as subsequent decomposition, in the alloys with shape memory effect of Cu–14wt%Al–3wt%Ni and Cu–13.5wt%Al–3.5wt%Ni. For the first time, we established the microstructure, phase composition, mechanical properties, and microhardness of the alloys obtained in the nanocrystalline state as a result of severe plastic deformation under high pressure torsion and subsequent annealing. A crystallographic model of the martensite nucleation and the rearrangements β₁→β₁′ and β₁→γ₁′ are proposed based on the analysis of the observed tweed contrast and diffuse scattering in the austenite and the internal defects in the substructure of the martensite. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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12 pages, 2066 KiB

Open AccessArticle

Simple and Precise Description of the Transformation Kinetics and Final Structure of Dual Phase Steels

by Jan Kohout

Materials 2021, 14(7), 1781; https://doi.org/10.3390/ma14071781 - 4 Apr 2021

Cited by 2 | Viewed by 1868

Abstract

The kinetics of diffusion-dependent phase transformations (including austenitisation of ferrite in dual steels or ferritic nodular cast irons) is very often described by the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. This description is not complete when the conversion is only partial due to insufficient overheating, as [...] Read more.

The kinetics of diffusion-dependent phase transformations (including austenitisation of ferrite in dual steels or ferritic nodular cast irons) is very often described by the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. This description is not complete when the conversion is only partial due to insufficient overheating, as the equilibrium fraction of ferrite transformed into austenite cannot be determined directly from the JMAK equation. Experimental kinetic curves of partial austenitisation at various temperatures can be fitted using the JMAK equation, but the equilibrium fraction of the newly formed phase for each temperature has to be calculated as a regression parameter. In addition, the temperature dependence of the kinetic exponent in the JMAK equation is quite complicated and cannot be expressed by a simple general function. On the contrary, the equation of autoinhibition used for the description of austenitisation kinetics in present work directly gives the equilibrium fraction at partial conversion. It describes transformation kinetics at various temperatures independently of whether the conversion is complete or partial. Rate constants of the equation of autoinhibition depend on temperature according to the Arrhenius equation. In addition, the equation of autoinhibition has no weakness as the JMAK equation has, which consists in questionable temperature dependence of kinetic exponent. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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13 pages, 17363 KiB

Open AccessArticle

The Effect of Different Thermal Treatment on the Allotropic fcc↔hcp Transformation and Compression Behavior of Polycrystalline Cobalt

by Michal Knapek, Peter Minárik, Patrik Dobroň, Jana Šmilauerová, Mayerling Martinez Celis, Eric Hug and František Chmelík

Materials 2020, 13(24), 5775; https://doi.org/10.3390/ma13245775 - 17 Dec 2020

Cited by 11 | Viewed by 2343

Abstract

Pure polycrystalline cobalt is systematically thermally treated in order to assess the effect of the microstructure on the compression behavior. Isothermal annealing of the as-drawn material leads to recrystallization and grain growth dependent on the annealing temperature (600–1100

^{\circ}

C). Consequently, the yield [...] Read more.

Pure polycrystalline cobalt is systematically thermally treated in order to assess the effect of the microstructure on the compression behavior. Isothermal annealing of the as-drawn material leads to recrystallization and grain growth dependent on the annealing temperature (600–1100

^{\circ}

C). Consequently, the yield strength decreases and the fracture strain increases as a function of rising grain size; the content of the residual fcc phase is ~6–11%. Subsequent thermal cycling around the transition temperature is applied to further modify the microstructure, especially in terms of the fcc phase content. With the increasing number of cycles, the grain size further increases and the fraction of the fcc phase significantly drops. At the same time, the values of both the yield strength and fracture strain somewhat decrease. An atypical decrease in the fracture strain as a function of grain size is explained in terms of decreasing fcc phase content; the stress-induced fcc→hcp transformation can accommodate a significant amount of plastic strain. Besides controlling basic material parameters (e.g., grain size and texture), adjusting the content of the fcc phase can thus provide an effective means of mechanical performance optimization with respect to particular applications. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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18 pages, 10848 KiB

Open AccessArticle

Influence and Sensitivity of Temperature and Microstructure on the Fluctuation of Creep Properties in Ni-Base Superalloy

by Zhihao Yao, Biao Zhou, Kaijun Yao, Hongying Wang, Jianxin Dong and Theresa Davey

Materials 2020, 13(21), 4758; https://doi.org/10.3390/ma13214758 - 24 Oct 2020

Cited by 4 | Viewed by 2327

Abstract

In this work, the sensitivity zone of microstructure and temperature for precipitation-strengthened nickel-based superalloys, used for turbine applications in aero-engines, has been firstly established. Heat treatment experiments with different solution temperatures were carried out. The microstructure evolution and creep residual strain sensitivity, low [...] Read more.

In this work, the sensitivity zone of microstructure and temperature for precipitation-strengthened nickel-based superalloys, used for turbine applications in aero-engines, has been firstly established. Heat treatment experiments with different solution temperatures were carried out. The microstructure evolution and creep residual strain sensitivity, low cycle fatigue properties, and tensile properties are analyzed, and the essential reason for the fluctuation of the mechanical properties of nickel-based superalloys was revealed. The main results obtained are as follows: following subsolvus solution heat treatment with a temperature of 1020 °C, samples have a high primary γ′_I phase content, which is beneficial to low creep residual strain. Above the supersolvus solution temperature of 1040 °C, the creep residual strain value and low cycle fatigue performance fluctuate significantly. The essential reason for the dramatic fluctuation of performance is the presence of γ′ phases in different sizes and quantities, especially following the solution heat treatment in the temperature-sensitive zone of the γ′_I phase, which is likely to cause huge fluctuations in the microstructure of tertiary γ′_III phases. A zone of particular sensitivity in terms of temperature and microstructure for the γ′_I phase is proposed. The range of suitable solution temperatures are discussed. In order to maintain stable mechanical properties without large fluctuations, the influence of the sensitivity within this temperature and microstructure zone on the γ′ phase should be considered. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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Review

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20 pages, 3944 KiB

Open AccessReview

Magnetic States and Electronic Properties of Manganese-Based Intermetallic Compounds Mn₂YAl and Mn₃Z (Y = V, Cr, Fe, Co, Ni; Z = Al, Ge, Sn, Si, Pt)

by Vyacheslav V. Marchenkov and Valentin Yu. Irkhin

Materials 2023, 16(19), 6351; https://doi.org/10.3390/ma16196351 - 22 Sep 2023

Cited by 1 | Viewed by 1819

Abstract

We present a brief review of experimental and theoretical papers on studies of electron transport and magnetic properties in manganese-based compounds Mn₂YZ and Mn₃Z (Y = V, Cr, Fe, Co, Ni, etc.; Z = Al, Ge, Sn, Si, [...] Read more.

We present a brief review of experimental and theoretical papers on studies of electron transport and magnetic properties in manganese-based compounds Mn₂YZ and Mn₃Z (Y = V, Cr, Fe, Co, Ni, etc.; Z = Al, Ge, Sn, Si, Pt, etc.). It has been shown that in the electronic subsystem of Mn₂YZ compounds, the states of a half-metallic ferromagnet and a spin gapless semiconductor can arise with the realization of various magnetic states, such as a ferromagnet, a compensated ferrimagnet, and a frustrated antiferromagnet. Binary compounds of Mn₃Z have the properties of a half-metallic ferromagnet and a topological semimetal with a large anomalous Hall effect, spin Hall effect, spin Nernst effect, and thermal Hall effect. Their magnetic states are also very diverse: from a ferrimagnet and an antiferromagnet to a compensated ferrimagnet and a frustrated antiferromagnet, as well as an antiferromagnet with a kagome-type lattice. It has been demonstrated that the electronic and magnetic properties of such materials are very sensitive to external influences (temperature, magnetic field, external pressure), as well as the processing method (cast, rapidly quenched, nanostructured, etc.). Knowledge of the regularities in the behavior of the electronic and magnetic characteristics of Mn₂YAl and Mn₃Z compounds can be used for applications in micro- and nanoelectronics and spintronics. Full article

(This article belongs to the Special Issue Phase Transformation and Properties of Metals and Alloys)

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