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Metals
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Heat Treatment and Mechanical Properties of Metals and Alloys
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Heat Treatment and Mechanical Properties of Metals and Alloys

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 July 2021) | Viewed by 57139

Special Issue Editor

Dr. Mariusz Król

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Guest Editor
Department of Engineering Materials and Biomaterials, Silesian University of Technology, 18A Konarskiego Street, 44-100 Gliwice, Poland
Interests: thermal analysis; mechanical properties; casting; alloy; light metals; additive manufacturing
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The main factors contributing to the functional properties of a metallic material are its chemical composition and the applied technologies which affect the material both directly and indirectly through its structure. Complex relationships exist not only between a technology and a material structure, but also between a material structure and its properties, including the behavior of metallic materials. The structure of a material, as a factor subject to a very wide range of changes and modifications, is important in shaping the material’s properties. The properties of metallic materials can be divided into those that are sensitive to changes in the material’s structure and those that do not show particular sensitivity to these changes. In general terms, heat treatment is a technological process that changes the mechanical and physicochemical properties of metals and solid alloys by causing changes of the structure that are mainly a function of temperature, time, and environmental conditions. Modern technology has specific requirements for the used materials. Also, metallic materials should be employed wisely in conditions that allow the optimal use of their potential functional properties. Heat treatment, to a certain extent, provides these conditions to metallic materials, shaping their structure both in their entire volume and on their surface. Any shortcomings in heat treatment technology negatively affect the properties of the finished products or the further production phase.

In this Special Issue, we seek to provide a wide set of articles on various aspects of heat treatment and thermal treatment and on the mechanical properties of metals and alloys. The idea is to demonstrate the power of heat treatment and how it influences the properties of metals and alloys. It is hoped that this open-access issue will provide a place for anyone to familiarize with the current state of the art in this field. Articles on heat treatment and thermal processing methods, thermomechanical treatment, cryogenic treatment, metallurgy, characterization, and evaluation of metallic materials are welcome.

Dr. Mariusz Król
Guest Editor

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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 2600 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

  • heat treatment
  • thermal treatment
  • thermomechanical treatment
  • metallurgy
  • microstructure
  • mechanical property
  • metals
  • alloys

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Related Special Issue

Published Papers (18 papers)

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Research

13 pages, 7866 KiB  
Article
Carbonitriding of Forging Dies
by Stefanie Hoja, Heinrich Klümper-Westkamp and Matthias Steinbacher
Metals 2021, 11(10), 1651; https://doi.org/10.3390/met11101651 - 18 Oct 2021
Cited by 3 | Viewed by 2284
Abstract
Forging dies have to resist high mechanical and thermal loads. Therefore, they are usually nitrided. Former investigations showed that the abrasive wear at the critical parts of the dies is much higher than the nitriding hardness depth. Carbonitriding offers the possibility to increase [...] Read more.
Forging dies have to resist high mechanical and thermal loads. Therefore, they are usually nitrided. Former investigations showed that the abrasive wear at the critical parts of the dies is much higher than the nitriding hardness depth. Carbonitriding offers the possibility to increase the hardness depth in shorter treatment times because of the higher treatment temperature. The (carbo-)nitrided surface region obtains a better hardness at elevated temperatures and a better wear resistance than the untreated steel. In order to create a wear- and corrosion-resistant compound layer at the surface, a nitriding process step can be conducted after carbonitriding. The present work deals with developing a carbonitriding treatment for forging dies and investigations on the wear resistance of the created surface zones in model wear tests and tool life time experiments under industrial conditions. The aim of this work was to produce heat- and wear-resistant precipitation layers in hot working tool steels in economical treatment durations. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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11 pages, 3034 KiB  
Article
Peculiarities of High-Energy Induction Heating during Surface Hardening in Hybrid Processing Conditions
by Vadim Y. Skeeba, Vladimir V. Ivancivsky and Nikita V. Martyushev
Metals 2021, 11(9), 1354; https://doi.org/10.3390/met11091354 - 28 Aug 2021
Cited by 19 | Viewed by 2304
Abstract
This paper presents the results obtained when combining mechanical and surface-thermal operations, using the same process equipment. The paper also demonstrates the possibility of implementing high-energy heating with high-frequency currents, and proposes using an integral temperature–time characteristic as the main parameter to specify [...] Read more.
This paper presents the results obtained when combining mechanical and surface-thermal operations, using the same process equipment. The paper also demonstrates the possibility of implementing high-energy heating with high-frequency currents, and proposes using an integral temperature–time characteristic as the main parameter to specify surface quenching modes. The numerical values of the integral temperature–time characteristic are to be related to the processing modes and the depth of hardening. The experiments confirmed that an increase in the capacity will be commensurate with an increase in power consumption when a volumetric heating scheme (with a hardening depth of 0.5 mm) is realized. However, during the realization of a volumetric heating scheme, when the 0.7 mm depth of the hardened layer is at the boundary of the “hot” depth of the current penetration into the metal (the beginning of the intermediate heating scheme), the increase in the processing capacity will be higher than that in power consumption. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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12 pages, 2097 KiB  
Article
The Role of Retained Austenite in Tempered Martensite Embrittlement of 4340 and 300-M Steels Investigated through Rapid Tempering
by Virginia K. Euser, Don L. Williamson, Kip O. Findley, Amy J. Clarke and John G. Speer
Metals 2021, 11(9), 1349; https://doi.org/10.3390/met11091349 - 27 Aug 2021
Cited by 13 | Viewed by 3155
Abstract
Tempered martensite embrittlement (TME) is investigated in two medium carbon, high strength steels, 4340 (low silicon) and 300-M (high silicon), via rapid (1, 10, or 100 s) and conventional (3600 s) tempering. Rapid tempering of 4340 diminishes the depth of the TME toughness [...] Read more.
Tempered martensite embrittlement (TME) is investigated in two medium carbon, high strength steels, 4340 (low silicon) and 300-M (high silicon), via rapid (1, 10, or 100 s) and conventional (3600 s) tempering. Rapid tempering of 4340 diminishes the depth of the TME toughness trough, where improvements in impact toughness correspond to the suppression of retained austenite decomposition. In 300-M, retained austenite decomposition is suppressed to an even greater extent by rapid tempering. While toughness improves overall after rapid tempering, TME severity remains consistent in 300-M across the tempering conditions examined. Through interrupted tensile tests, it was found that the 300-M conditions that exhibit TME are associated with mechanically unstable retained austenite. Unstable retained austenite is shown to mechanically transform early in the deformation process, presumably resulting in fresh martensite adjacent to interlath cementite that ultimately contributes to TME. The present results emphasize the role of both the thermal decomposition and mechanical transformation of retained austenite in the manifestation of TME. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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17 pages, 7530 KiB  
Article
Experimental Investigation on Tensile Properties and Yield Strength Modeling of T5 Heat-Treated Counter Pressure Cast A356 Aluminum Alloys
by Sang-Won Kim, Seok-Jae Lee, Dae-Up Kim and Min-Su Kim
Metals 2021, 11(8), 1192; https://doi.org/10.3390/met11081192 - 26 Jul 2021
Cited by 8 | Viewed by 2926
Abstract
In the present study, experimental investigations on microstructures and tensile properties of an counter-pressure cast (CPC) A356 aluminum alloy under different T5 heat treatment conditions were conducted in the temperature range of 160–200 ∘C for 1–48 h. As the T5 heat treatment [...] Read more.
In the present study, experimental investigations on microstructures and tensile properties of an counter-pressure cast (CPC) A356 aluminum alloy under different T5 heat treatment conditions were conducted in the temperature range of 160–200 ∘C for 1–48 h. As the T5 heat treatment time increased, both tensile and yield strength of the CPC A356 alloy either continuously increased at 160 ∘C until 48 h of heat treatment time or increased until the maximum strength values were achieved and then decreased, showing peak aging behavior at 180 and 200 ∘C. Changes in microstructural aspects, such as size and aspect ratio, of the eutectic Si, Mg and Si distribution in the α-Al grain and the stability of intermetallic compounds were found to be negligible during the T5 heat treatments employed in the present study. From high resolution-transmission electron microscope (HR-TEM) analysis, nanosized needle-like β″ precipitates were identified in the specimens, showing a significant increase in strength after the T5 heat treatment. Based on the measured tensile properties and observed microstructure changes, a yield strength model was proposed to predict yield strengths of CPC A356 alloys at arbitrary T5 heat treatment conditions. The calculation results of the model showed good agreement with the experimental data obtained in the present study. From the model calculations, the optimal T5 heat treatment time or temperature conditions were suggested. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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10 pages, 1914 KiB  
Article
Thermophysical Properties of Pipe Steel in the Liquid State
by Vladimir S. Tsepelev, Yuri N. Starodubtsev and Nadezhda P. Tsepeleva
Metals 2021, 11(7), 1099; https://doi.org/10.3390/met11071099 - 10 Jul 2021
Cited by 2 | Viewed by 2023
Abstract
The temperature dependences of the kinematic viscosity and surface tension of liquid pipe steel with different modes of melt preparation were investigated. A transition zone was found on the temperature dependences of the thermophysical properties, which separates the regions with different activation energies [...] Read more.
The temperature dependences of the kinematic viscosity and surface tension of liquid pipe steel with different modes of melt preparation were investigated. A transition zone was found on the temperature dependences of the thermophysical properties, which separates the regions with different activation energies of viscous flow and surface tension. At the heating stage in the transition zone, the thermal decomposition of clusters based on cementite Fe3C occurs. As a result of the decomposition, free carbon atoms appear which tend to give a uniform distribution in liquid iron with increasing temperature. At a low content of alloying elements and impurities, a high-temperature melt should have a large-scale cluster structure, which provides a more uniform distribution of chemical elements. The melt after vacuum degassing has a narrow transition zone near 1920 K, in contrast to the wide transition zone of the melt without vacuum degassing. The wider transition zone is shifted to high-temperature and this shift is associated with the thermal decomposition of carbides and oxides. Studies have shown that heating liquid pipe steel above the temperature of the liquid–liquid structural transition makes it possible to obtain a more homogeneous structure with a more uniform distribution of alloying and impurity elements in the melt. The sharp drop in surface tension at temperatures above 1920 K in the melt without vacuum degassing is associated with the diffusion of free S and O atoms, which are released after thermal decomposition of sulfides and oxides. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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13 pages, 5590 KiB  
Article
Effect of Cooling Rate on Hardness and Phase Transformation of a Pd-Ag-Based Metal–Ceramic Alloy with or without Ice-Quenching
by Hye-Jeong Shin, Yong-Hoon Kwon and Hyo-Joung Seol
Metals 2021, 11(5), 680; https://doi.org/10.3390/met11050680 - 21 Apr 2021
Cited by 1 | Viewed by 1668
Abstract
The aim of this study was to investigate the effect of cooling rate on the hardness and phase transformation of a Pd-Ag-based metal–ceramic alloy with or without ice-quenching. A total of 28 test specimens, in an as-cast state, were fabricated. A multiple firing [...] Read more.
The aim of this study was to investigate the effect of cooling rate on the hardness and phase transformation of a Pd-Ag-based metal–ceramic alloy with or without ice-quenching. A total of 28 test specimens, in an as-cast state, were fabricated. A multiple firing simulation was performed on the randomly selected specimens (n = 3/group) in a porcelain furnace; each firing was followed by cooling at the relatively low or high cooling rate. In addition, ice-quenching after oxidation was introduced before the normal firing process (n = 3/group). Microhardness, microstructure, phase transformation and elemental distribution were observed. Oxidation followed by ice-quenching allowed the alloy to be in a homogenized state. On the other hand, the oxidation-treated specimens followed by cooling at relatively high or low cooling speeds showed much higher hardness than the ice-quenched specimen after oxidation, which was resulted from the formation of the metastable precipitates based on the InPd3 phase with tetragonal structure. The hardness of ice-quenched alloy after oxidation was recovered in the very next firing step at both the relatively high and low cooling rates. In all specimens, the Pd-rich matrix and the InPd3-based precipitates were observed. The hardness of a Pd-Ag-based metal–ceramic alloy with and without ice-quenching depended on the cooling rate during the firing process. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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21 pages, 14093 KiB  
Article
Effect of Alloying Additives and Microadditives on Hardenability Increase Caused by Action of Boron
by Beata Białobrzeska
Metals 2021, 11(4), 589; https://doi.org/10.3390/met11040589 - 4 Apr 2021
Cited by 15 | Viewed by 3322
Abstract
The presented work was aimed at evaluating influence of boron on hardenability of steel quantitatively and evaluating this effect during complex use of boron with other alloying additives like chromium, vanadium and titanium. For this purpose, eight melts with variable chemical compositions were [...] Read more.
The presented work was aimed at evaluating influence of boron on hardenability of steel quantitatively and evaluating this effect during complex use of boron with other alloying additives like chromium, vanadium and titanium. For this purpose, eight melts with variable chemical compositions were prepared. From the ingots, cylindrical specimens with normalized dimensions according to EN ISO 642:1999 were cut out and subjected to full annealing at 1200 °C and to normalizing at 900 °C. Such specimens were subjected to the hardenability Jominy test. In order to distinguish the influence of boron on hardenability of a given melt and thus to eliminate the differences resulting from its chemical composition, grain size and austenitizing temperature, the obtained ideal critical diameter was corrected and the boron effectiveness factor was determined. The performed examinations and analyses showed that inadequate quantities of microadditives result in losing the benefits coming from introduction of boron as the hardenability-improving element and can even result in a reduction of hardenability of the boron-containing steel. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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13 pages, 3678 KiB  
Article
Influence of Pre-Aging on the Artificial Aging Behavior of a 6056 Aluminum Alloy after Conventional Extrusion
by Lisa Winter, Kristin Hockauf, Mario Scholze, Ralph Jörg Hellmig and Thomas Lampke
Metals 2021, 11(3), 385; https://doi.org/10.3390/met11030385 - 26 Feb 2021
Cited by 9 | Viewed by 2902
Abstract
In the present study, the influence of the initial heat-treatment conditions on the artificial aging behavior after conventional linear extrusion at room temperature was investigated for the precipitation hardening of a 6056 aluminum alloy. A solution-annealed condition was systematically compared to naturally-aged and [...] Read more.
In the present study, the influence of the initial heat-treatment conditions on the artificial aging behavior after conventional linear extrusion at room temperature was investigated for the precipitation hardening of a 6056 aluminum alloy. A solution-annealed condition was systematically compared to naturally-aged and pre-aged conditions. Differential scanning calorimetry was used for analyzing the precipitation sequence and its dependence on the initial heat treatment. The natural aging behavior prior to extrusion and the artificial aging behavior after extrusion were determined by microhardness measurements as a function of the aging time. Furthermore, the microstructure, dependent on the induced strain, was investigated using optical microscopy and transmission electron microscopy. As a result of pre-aging, following a solid-solution treatment, the formation of stable room-temperature clusters was suppressed and natural aging was inhibited. The artificial aging response after extrusion was significantly enhanced by pre-aging, and the achieved hardness and strength were significantly higher when compared with the equally processed solution-annealed or naturally-aged conditions. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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12 pages, 5191 KiB  
Article
Comparison of Industrial Quenching Oils
by Jiří Hájek, Zaneta Dlouha and Vojtěch Průcha
Metals 2021, 11(2), 250; https://doi.org/10.3390/met11020250 - 2 Feb 2021
Cited by 3 | Viewed by 3770
Abstract
This article is a response to the state of the art in monitoring the cooling capacity of quenching oils in industrial practice. Very often, a hardening shop requires a report with data on the cooling process for a particular quenching oil. However, the [...] Read more.
This article is a response to the state of the art in monitoring the cooling capacity of quenching oils in industrial practice. Very often, a hardening shop requires a report with data on the cooling process for a particular quenching oil. However, the interpretation of the data can be rather difficult. The main goal of our work was to compare various criteria used for evaluating quenching oils. Those of which prove essential for operation in tempering plants would then be introduced into practice. Furthermore, the article describes monitoring the changes in the properties of a quenching oil used in a hardening shop, the effects of quenching oil temperature on its cooling capacity and the impact of the water content on certain cooling parameters of selected oils. Cooling curves were measured (including cooling rates and the time to reach relevant temperatures) according to ISO 9950. The hardening power of the oil and the area below the cooling rate curve as a function of temperature (amount of heat removed in the nose region of the Continuous cooling transformation - CCT curve) were calculated. V-values based on the work of Tamura, reflecting the steel type and its CCT curve, were calculated as well. All the data were compared against the hardness and microstructure on a section through a cylinder made of EN C35 steel cooled in the particular oil. Based on the results, criteria are recommended for assessing the suitability of a quenching oil for a specific steel grade and product size. The quenching oils used in the experiment were Houghto Quench C120, Paramo TK 22, Paramo TK 46, CS Noro MO 46 and Durixol W72. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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14 pages, 1563 KiB  
Article
Prediction of Microstructure Constituents’ Hardness after the Isothermal Decomposition of Austenite
by Sunčana Smokvina Hanza, Božo Smoljan, Lovro Štic and Krunoslav Hajdek
Metals 2021, 11(2), 180; https://doi.org/10.3390/met11020180 - 20 Jan 2021
Cited by 7 | Viewed by 2762
Abstract
An increase in technical requirements related to the prediction of mechanical properties of steel engineering components requires a deep understanding of relations which exist between microstructure, chemical composition and mechanical properties. This paper is dedicated to the research of the relation between steel [...] Read more.
An increase in technical requirements related to the prediction of mechanical properties of steel engineering components requires a deep understanding of relations which exist between microstructure, chemical composition and mechanical properties. This paper is dedicated to the research of the relation between steel hardness with the microstructure, chemical composition and temperature of isothermal decomposition of austenite. When setting the equations for predicting the hardness of microstructure constituents, it was assumed that: (1) The pearlite hardness depends on the carbon content in a steel and on the undercooling below the critical temperature, (2) the martensite hardness depends primarily on its carbon content, (3) the hardness of bainite can be between that of untempered martensite and pearlite in the same steel. The equations for estimation of microstructure constituents’ hardness after the isothermal decomposition of austenite have been proposed. By the comparison of predicted hardness using a mathematical model with experimental results, it can be concluded that hardness of considered low-alloy steels could be successfully predicted by the proposed model. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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19 pages, 26702 KiB  
Article
Analysis of the Properties of Hardox Extreme Steel and Possibilities of Its Applications in Machinery
by Beata Białobrzeska, Robert Jasiński, Łukasz Konat and Łukasz Szczepański
Metals 2021, 11(1), 162; https://doi.org/10.3390/met11010162 - 17 Jan 2021
Cited by 17 | Viewed by 5078
Abstract
The article presents the results of Hardox Extreme steel tests in the as-delivered state from a steel mill (after quenching and tempering), and also in the normalized state. The research procedures included a microstructure analysis using light microscopy; and a static tensile test [...] Read more.
The article presents the results of Hardox Extreme steel tests in the as-delivered state from a steel mill (after quenching and tempering), and also in the normalized state. The research procedures included a microstructure analysis using light microscopy; and a static tensile test at ambient temperature to determine its Young’s modulus, yield strength, tensile strength, elongation and reduction in area after fracture. During the tensile tests, both the longitudinal and transverse orientation of rolling direction were taken into account. The Charpy impact test was also carried out in the temperature range of the ductile–brittle transition in connection with the fractographic analysis carried out with the use of a scanning microscope (SEM). The impact tests were carried out on samples in both directions on the plate, using the following temperatures: −40, −20, 0, +20 °C. Based on the structural and strength characteristics of Hardox Extreme steel determined on the basis of the research, in a further part of the paper the possibility of its use in machine construction elements operating in selected industrial sectors is considered/discussed, with a particular emphasis on reducing the level of energy consumption in the manufacturing and operation of the above technical facilities. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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17 pages, 14069 KiB  
Article
Optimization Study of Post-Weld Heat Treatment for 12Cr1MoV Pipe Welded Joint
by Zichen Liu, Xiaodong Hu, Zhiwei Yang, Bin Yang, Jingkai Chen, Yun Luo and Ming Song
Metals 2021, 11(1), 127; https://doi.org/10.3390/met11010127 - 10 Jan 2021
Cited by 9 | Viewed by 3246
Abstract
In order to clarify the role of different post-weld heat treatment processes in the manufacturing process, welding tests, post-weld heat treatment tests, and finite element analysis (FEA) are carried out for 12C1MoV steel pipes. The simulated temperature field and residual stress field agree [...] Read more.
In order to clarify the role of different post-weld heat treatment processes in the manufacturing process, welding tests, post-weld heat treatment tests, and finite element analysis (FEA) are carried out for 12C1MoV steel pipes. The simulated temperature field and residual stress field agree well with the measured results, which indicates that the simulation method is available. The influence of post-weld heat treatment process parameters on residual stress reduction results is further analyzed. It is found that the post weld dehydrogenation treatment could not release residual stress obviously. However, the residual stress can be relieved by 65% with tempering treatment. The stress relief effect of “post weld dehydrogenation treatment + temper heat treatment” is same with that of “temper heat treatment”. The higher the temperature, the greater the residual stress reduction, when the peak temperature is at 650–750 °C, especially for the stress concentration area. The longer holding time has no obvious positive effect on the reduction of residual stress. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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22 pages, 1866 KiB  
Article
Multi-Criteria Selection of the Optimal Parameters for High-Speed Machining of Aluminum Alloy Al7075 Thin-Walled Parts
by Dejan Lukic, Robert Cep, Jovan Vukman, Aco Antic, Mica Djurdjev and Mijodrag Milosevic
Metals 2020, 10(12), 1570; https://doi.org/10.3390/met10121570 - 24 Nov 2020
Cited by 29 | Viewed by 3430
Abstract
Thin-walled parts made of aluminum alloy are mostly used as structural elements in the aerospace, automobile, and military industries due to good homogeneity, corrosion resistance, and the excellent ratio between mechanical properties and mass. Manufacturing of these parts is mainly performed by removing [...] Read more.
Thin-walled parts made of aluminum alloy are mostly used as structural elements in the aerospace, automobile, and military industries due to good homogeneity, corrosion resistance, and the excellent ratio between mechanical properties and mass. Manufacturing of these parts is mainly performed by removing a large volume of material, so it is necessary to choose quality machining parameters that will achieve high productivity and satisfactory quality and accuracy of machining. Using the Taguchi methodology, an experimental plan is created and realized. Based on its results and comparative analysis of multi-criteria decision making (MCDM) methods, optimal levels of machining parameters in high-speed milling of thin-walled parts made of aluminum alloy Al7075 are selected. The varying input parameters are wall thickness, cutting parameters, and tool path strategies. The output parameters are productivity, surface quality, dimensional accuracy, the accuracy of forms and surface position, representing the optimization criteria. Selection of the optimal machining parameter levels and their ranking is realized using 14 MCDM methods. Afterward, the obtained results are compared using correlation analysis. At the output, integrative decisions were made on selecting the optimal level and rank of alternative levels of machining parameters. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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25 pages, 11093 KiB  
Article
Quantification of the Dislocation Density, Size, and Volume Fraction of Precipitates in Deep Cryogenically Treated Martensitic Steels
by Ajesh Antony, Natalya M. Schmerl, Anna Sokolova, Reza Mahjoub, Daniel Fabijanic and Nikki E. Stanford
Metals 2020, 10(11), 1561; https://doi.org/10.3390/met10111561 - 23 Nov 2020
Cited by 9 | Viewed by 3248
Abstract
Two groups of martensitic alloys were examined for changes induced by deep cryogenic treatment (DCT). The first group was a range of binary and ternary compositions with 0.6 wt % carbon, and the second group was a commercial AISI D2 tool steel. X-ray [...] Read more.
Two groups of martensitic alloys were examined for changes induced by deep cryogenic treatment (DCT). The first group was a range of binary and ternary compositions with 0.6 wt % carbon, and the second group was a commercial AISI D2 tool steel. X-ray diffraction showed that DCT made two changes to the microstructure: retained austenite was transformed to martensite, and the dislocation density of the martensite was increased. This increase in dislocation density was consistent for all alloys, including those that did not undergo phase transformation during DCT. It is suggested that the increase in dislocation density may be caused by local differences in thermal expansion within the heterogeneous martensitic structure. Then, samples were tempered, and the cementite size distribution was examined using small angle neutron scattering (SANS) and atom probe tomography. First principles calculations confirmed that all magnetic scattering originated in cementite and not carbon clusters. Quantitative SANS analysis showed a measurable change in cementite size distribution for all alloys as a result of prior DCT. It is proposed that the increase in dislocation density that results from DCT modifies the cementite precipitation through enhanced diffusion rates and increased cementite nucleation sites. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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9 pages, 8148 KiB  
Article
Effect of Heat Treatment on Microstructure and Mechanical Properties of New Cold-Rolled Automotive Steels
by Fei Huang, Jian Chen, Zhangqi Ge, Junliang Li and Yongqiang Wang
Metals 2020, 10(11), 1414; https://doi.org/10.3390/met10111414 - 24 Oct 2020
Cited by 6 | Viewed by 2781
Abstract
The effect of austenitizing temperature and aging treatment on the microstructure and mechanical properties of two new cold-rolled automotive steel plates (20Mn2Cr and 20Mn2CrNb) was investigated by using isothermal heat treatment, optical microscope, scanning electron microscope, microhardness tester, and tensile testing machine. The [...] Read more.
The effect of austenitizing temperature and aging treatment on the microstructure and mechanical properties of two new cold-rolled automotive steel plates (20Mn2Cr and 20Mn2CrNb) was investigated by using isothermal heat treatment, optical microscope, scanning electron microscope, microhardness tester, and tensile testing machine. The results show that as the austenitizing temperature increased, the original austenite grain sizes of both steels increased. The original austenite grain size of 20Mn2CrNb was smaller than that of 20Mn2Cr. The microhardness of 20Mn2CrNb gradually decreased with increasing aging temperature, while the hardness of 20Mn2Cr varied irregularly. The mechanical properties of 20Mn2Cr were better than those of 20Mn2CrNb under the same heat-treatment process. The effect of heat treatment on microstructure and mechanical properties was related to the martensite content, dislocation density, and precipitation of second-phase particles. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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15 pages, 13088 KiB  
Article
Effect of Heat Treatment and Drawing on High-Manganese Steel Pipe Welded by Gas Tungsten Arc
by Geon-Woo Park, Haeju Jo, Minha Park, Byung-Jun Kim, Wookjin Lee, Sunmi Shin, Sung Soo Park, Yong-Sik Ahn and Jong Bae Jeon
Metals 2020, 10(10), 1366; https://doi.org/10.3390/met10101366 - 13 Oct 2020
Cited by 6 | Viewed by 3209
Abstract
This study investigated the effect of post-weld processes including annealing and drawing on the microstructure and mechanical properties of high-Mn steel pipes welded by gas tungsten arc welding. The weld metal showed a solidified microstructure having coarse and elongated grains due to coalescence [...] Read more.
This study investigated the effect of post-weld processes including annealing and drawing on the microstructure and mechanical properties of high-Mn steel pipes welded by gas tungsten arc welding. The weld metal showed a solidified microstructure having coarse and elongated grains due to coalescence of columnar dendrite into welding heat direction. After post-annealing, the solidified microstructure changed into equiaxed grains due to recrystallization and grain growth. Mn segregation occurred during welding solidification and caused lower stacking fault energy (SFE) in the Mn-depleted region. Although ε-martensite formation in the as-welded state and during deformation was expected due to decreased SFE of the Mn-depleted zone, all regions showed a fully austenitic phase. The annealing process decreased strength due to grain coarsening but increased ductility. The drawing process increased strength of weld metal through work hardening. All pipes showed decreasing strain rate sensitivity (SRS) with deformation and negative SRS after certain strain levels. It was confirmed that negative SRS is related to less formation of mechanical twinning at a higher strain rate. This work provides fundamental insights into manufacturing a high-Mn steel pipe and manipulating its properties with annealing and drawing processes. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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14 pages, 4072 KiB  
Article
Effect of Heat Treatment on Microstructure and Mechanical Properties of Mg-5Zn-1Mn Alloy Tube
by Lianhui Li, Hongshuai Cao, Fugang Qi, Qing Wang, Nie Zhao, Yingdu Liu, Xue Ye and Xiaoping Ouyang
Metals 2020, 10(3), 301; https://doi.org/10.3390/met10030301 - 26 Feb 2020
Cited by 11 | Viewed by 3283
Abstract
The effects of heat treatment on the microstructure, mechanical properties and electrochemical property of the as-extruded Mg-5Zn-1Mn (ZM51) alloy tube are investigated by optical microstructure (OM), X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electrical microscope (TEM), uniaxial tensile test, and electrochemical test. [...] Read more.
The effects of heat treatment on the microstructure, mechanical properties and electrochemical property of the as-extruded Mg-5Zn-1Mn (ZM51) alloy tube are investigated by optical microstructure (OM), X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electrical microscope (TEM), uniaxial tensile test, and electrochemical test. The results show that the as-cast structure is a typical dendritic structure, mainly composed of α-Mg and Mg7Zn3 eutectic compounds. After homogenization, most of Mg7Zn3 eutectic phases are dissolved in the Mg matrix. During the extrusion process, the ZM51 alloy has undergone complete dynamic recrystallization and has a good elongation, reaching 21.4%. T6, especially T4 + double aging treatment, can significantly improve the mechanical properties of the as-extruded tube. The microstructure reveals that the precipitation strengthening of the finely dispersed MgZn2 precipitates is the main reason for the strength increase. The fracture micromorphology of the as-extruded tube is mainly composed of dimples and cleavage facets, which is a typical ductile fracture. The fracture mode of the as-aged alloy tubes belongs to cleavage fracture. In addition, the electrochemical test results show the solution-treated ZM51 alloy tube has the best corrosion resistance. The improvement of corrosion resistance is mainly due to the microstructure uniformity and low phase volume fraction. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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15 pages, 12584 KiB  
Article
Quantitative Relationships between Mechanical Properties and Microstructure of Ti17 Alloy after Thermomechanical Treatment
by Yan Han, Fei Zhao, Yuan Liu and Chaowen Huang
Metals 2020, 10(1), 67; https://doi.org/10.3390/met10010067 - 1 Jan 2020
Cited by 4 | Viewed by 3062
Abstract
In this paper, the relationships between the thermomechanical treatments (TMT), the microstructural evolution the mechanical properties of Ti17 alloy were investigated. The results indicate the coarsening behavior of lamellar α was sensitive to the aging temperature during the process of TMT. The thickness [...] Read more.
In this paper, the relationships between the thermomechanical treatments (TMT), the microstructural evolution the mechanical properties of Ti17 alloy were investigated. The results indicate the coarsening behavior of lamellar α was sensitive to the aging temperature during the process of TMT. The thickness of lamellar α changed from 0.19 to 0.38 μm with an increase in the aging temperature. Moreover, both tensile properties and impact toughness vary with the thickness of lamellar α. The tensile strength increases with the increase of the thickness of lamellar α the plasticity and impact toughness the opposite trend. The quantitative investigations found that there is a linear relationship between the tensile properties and the thickness of lamellar α the tensile properties could be adjusted in the range of 1191~1062 MPa and 1163~1039 MPa to obtain ultimate tensile strength and yield strength as well as 11~16% elongation and 23~33% reduction of area by varying the thickness of lamellar α. Meanwhile, the impact toughness could be adjusted in the range of 46 ~53 J/cm2. The high correlation coefficients imply that the linear equation is reliable to describe the relationships between the mechanical properties and the thickness of lamellar α for Ti17 alloy. Full article
(This article belongs to the Special Issue Heat Treatment and Mechanical Properties of Metals and Alloys)
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