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Microstructure-Mechanical Property Relationships in Metallic Materials

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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 (28 February 2022) | Viewed by 32112

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Special Issue Editors

Dr. Matjaž Godec

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Guest Editor

Institute of Metals and Technology Ljubljana, Ljubljana, Slovenia
Interests: metallic materials characterization (SEM/EDS/WDS/EBSD/ECCI, AES, XPS); physical chemistry of metallic surfaces; rapid solidification technology; tool steel carbide transformation; EBSD analysis of carbides and AM materials; R&D of soft magnetic composites; R&D of different steel grades; R&D of aluminum alloys; nickel super alloys; additive manufacturing; biocompatible and bioresorbable metallic materials

Dr. Danijela Skobir Balantič

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Guest Editor

Institute of Metals and Technology Ljubljana, Ljubljana, Slovenia
Interests: creep-resistant steels; additive materials; mechanical testing (tensile, fracture toughness, creep, fatigue); metallic materials characterization (SEM/EDS)

Special Issue Information

Dear Colleagues,

The mechanical properties of metallic materials are dependent on their microstructural features, such as grain and sub-grain sizes, grain-boundary phases, their morphology and distribution, dislocations, and dispersed particles. These microstructural features are a consequence of the metallic elements in the alloy, the conditions employed to produce the alloy, such as temperature, pressure and cooling rate, and any subsequent heat treatments and/or mechanical procedures. Thus, in order to understand the behavior of metallic materials, we need a better understanding of the structure at the micro, nano and atomic levels, usually based on an optical, electronic or mechanical response. This information can then be used to explain why a metallic material behaves in a certain way, and in some cases to predict the behavior of a material that exhibits a particular structure.

The Special Issue will cover new findings on how microstructures evolve as a result of different processing technologies, from the conventional to new forms such as additive manufacturing, different thermomechanical treatments, as well as a variety of analytical techniques that can be used to explain the mechanical properties. Manuscripts that describe new experimental and theoretical studies on the structure of materials would be welcome in this issue.

Dr. Matjaž Godec
Dr. Danijela Skobir Balantič
Guest Editors

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 submissions that pass pre-check are 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 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

Microstructure
Grain size
Grain boundary
Dislocations
Precipitates
Mechanical properties
Tensile strength
Ductility
Hardness
Heat treatment

Published Papers (12 papers)

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Research

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39 pages, 11803 KiB

Open AccessArticle

Computational Determination of Macroscopic Mechanical and Thermal Material Properties for Different Morphological Variants of Cast Iron

by Christoph Herrmann, Stefan Schmid, Daniel Schneider, Michael Selzer and Britta Nestler

Metals 2021, 11(10), 1588; https://doi.org/10.3390/met11101588 - 05 Oct 2021

Cited by 1 | Viewed by 1918

Abstract

The sensitivity of macroscopic mechanical and thermal properties of grey cast iron is computationally investigated for a variety of graphite morphologies over a wide temperature range. In order to represent common graphite morphologies according to EN ISO 945-1, a synthetic approach is used to algorithmically generate simulation domains. The developed mechanical and thermal model is applied in a large simulation study. The study includes statistical volume elements of the graphite morphology classes GJL-150 and IA2 to IA5, with 10, 11 and 12

v . - %

of graphite precipitations, respectively, for a temperature range from 20 to 750 °C. Homogenised macroscopic quantities, such as the Young’s moduli, Poisson’s ratios, yield strengths and thermal conductivities, are predicted for different morphology classes by applying simulation and data analysis tools of the research data infrastructure Kadi4Mat. This is the first work to determine the mechanical and thermal properties of the morphology classes defined in EN ISO 945-1. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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10 pages, 2812 KiB

Open AccessArticle

Microstructure and Nanoindentation Behavior of Ti₄₀Zr₄₀Ni₂₀ Quasicrystal Alloy by Casting and Rapid Solidification

by Junli Hou, Zhong Yang, Hongbo Duan, Yiyi Feng, Yongchun Guo and Jianping Li

Metals 2021, 11(10), 1563; https://doi.org/10.3390/met11101563 - 30 Sep 2021

Viewed by 1562

Abstract

A Ti₄₀Zr₄₀Ni₂₀ quasicrystal (QCs) rod and ribbons were prepared by conventional casting and rapid solidification. The X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential scanning calorimeter (DSC) techniques were used to investigate the microtissue, phase composition, and solidification features of the samples; the nano-indentation test was carried out at room temperature. The results show that a mixture of the α-Ti(Zr) phase and the icosahedral quasicrystal (I-phase) was formed in the Ti₄₀Zr₄₀Ni₂₀ rod; the microstructure of Ti₄₀Zr₄₀Ni₂₀ ribbons mainly consisted of the I-phase. The solidification mechanism of the I-phase was different in the two alloys. The I-phase in the quasicrystalline rod was formed by packet reaction while in the ribbons it was generated directly from the liquid. At room temperature, both samples had relatively high hardness and elastic modulus; the elastic modulus of the ribbons is 76 GPa, higher than the 45 GPa of the rod. The hardness of the ribbons was more than twice that of the rod. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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12 pages, 6697 KiB

Open AccessArticle

Effects of Sequential Operation with Heat Treatment and Mechanical Milling on Work Hardening for Superalloy GH4169

by Pingzhong Zhu, Zhanqiang Liu, Xiaoping Ren, Bing Wang and Qinghua Song

Metals 2021, 11(9), 1367; https://doi.org/10.3390/met11091367 - 30 Aug 2021

Cited by 2 | Viewed by 1628

Abstract

Engineering components are usually manufactured with sequential production processes. Work hardening due to previous production processes affects the machinability of the workpiece in subsequent operations. In this research, the surface work hardening of a workpiece manufactured by two sequential processes with heat treatment/milling (HT + M) and milling/heat treatment (M + HT) of superalloy GH4169 was investigated. First, the surface microstructure characteristics, including plastic deformation and grain size of the machined workpiece surface processed by the two sequential processes, were quantitatively presented. Then, the microhardness on the machined workpiece surface and its cross-section was measured and analyzed. Finally, a surface microhardness calculation model considering twin boundary deformation was proposed. Here, we also present the microstructure evolution principle of the machined workpiece surface by the two sequential processes. It was found that the degree of work hardening of HT + M machining was 179%, whereas that of M + HT was only 101%. The research results can be applied to the optimized selection of process sequence for manufacturing superalloy GH4169. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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11 pages, 8379 KiB

Open AccessArticle

Formation and Evolution of DS-Type Inclusions in 15-5PH Stainless Steel

by Zhonghua Zhan, Weifeng Zhang, Yanling Zhang, Ruxing Shi and Guoguang Cheng

Metals 2021, 11(7), 1129; https://doi.org/10.3390/met11071129 - 16 Jul 2021

Cited by 2 | Viewed by 1811

Abstract

15-5PH stainless steel castings are key components in fracturing trucks. However, DS-type inclusions can lead to fatigue failure of the material. To elucidate the formation mechanism of large-size DS-type inclusions, the evolution, growth, and aggregation of inclusions during vacuum oxygen decarburization, ladle refining, and vacuum casting were studied. The results show that the DS-type inclusions with sizes larger than 20 μm were CaO–Al₂O₃–SiO₂–MgO–CaS composite inclusions. After Si–Al additions in vacuum degassing, typical inclusions were spinel or Al₂O₃. After Ca–Si additions during ladle treatment, typical inclusions were liquid or dual-phase Al₂O₃–CaO–SiO₂–MgO. During the solidification process, due to the segregation of S and the decrease in solubility, the typical inclusions in the final casting became Al₂O₃–CaO–SiO₂–MgO–CaS. For optimal fatigue performance of stainless steel castings, slag and refractory composition control were also necessary because the [Mg] contents mainly come from the slag and lining. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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16 pages, 5578 KiB

Open AccessArticle

Grain Size Evolution and Mechanical Properties of Nb, V–Nb, and Ti–Nb Boron Type S1100QL Steels

by Jan Foder, Jaka Burja and Grega Klančnik

Metals 2021, 11(3), 492; https://doi.org/10.3390/met11030492 - 16 Mar 2021

Cited by 7 | Viewed by 2903

Abstract

Titanium additions are often used for boron factor and primary austenite grain size control in boron high- and ultra-high-strength alloys. Due to the risk of formation of coarse TiN during solidification the addition of titanium is limited in respect to nitrogen. The risk of coarse nitrides working as non-metallic inclusions formed in the last solidification front can degrade fatigue properties and weldability of the final product. In the presented study three microalloying systems with minor additions were tested, two without any titanium addition, to evaluate grain size evolution and mechanical properties with pre-defined as-cast, hot forging, hot rolling, and off-line heat-treatment strategy to meet demands for S1100QL steel. Microstructure evolution from hot-forged to final martensitic microstructure was observed, continuous cooling transformation diagrams of non-deformed austenite were constructed for off-line heat treatment, and the mechanical properties of Nb and V–Nb were compared to Ti–Nb microalloying system with a limited titanium addition. Using the parameters in the laboratory environment all three micro-alloying systems can provide needed mechanical properties, especially the Ti–Nb system can be successfully replaced with V–Nb having the highest response in tensile properties and still obtaining satisfying toughness of 27 J at –40 °C using Charpy V-notch samples. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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16 pages, 12522 KiB

Open AccessFeature PaperArticle

Effect of Intercritical Annealing on the Microstructure and Mechanical Properties of 0.1C-13Cr-3Ni Martensitic Stainless Steel

by Jaka Burja, Blaž Šuler, Marko Češnjaj and Aleš Nagode

Metals 2021, 11(3), 392; https://doi.org/10.3390/met11030392 - 27 Feb 2021

Cited by 7 | Viewed by 2715

Abstract

Standard heat treatment of martensitic stainless steel consists of quenching and tempering. However, this results in high strength and hardness, while Charpy impact toughness shows lower values and a large deviation in its values. Therefore, a modified heat treatment of 0.1C-13Cr-3Ni martensitic stainless steel (PK993/1CH13N3) with intercritical annealing between Ac1 and Ac3 was introduced before tempering to study its effect on the microstructure and mechanical properties (yield strength, tensile strength, hardness and Charpy impact toughness). The temperatures of intercritical annealing were 740, 760, 780 and 800 °C. ThermoCalc was used for thermodynamic calculations. Microstructure characterization was performed on an optical and scanning electron microscope, while XRD was used for the determination of retained austenite. Results show that intercritical annealing improves impact toughness and lowers deviation of its values. This can be attributed to the dissolution of the thin carbide film along prior austenite grain boundaries and prevention of its re-occurrence during tempering. On the other hand, lower carbon concentration in martensite that was quenching from the intercritical region resulted in lower strength and hardness. Intercritical annealing refines the martensitic microstructure creating a lamellar morphology. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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11 pages, 6101 KiB

Open AccessFeature PaperArticle

Thermodynamic Behavior of Fe-Mn and Fe-Mn-Ag Powder Mixtures during Selective Laser Melting

by Jakob Kraner, Jožef Medved, Matjaž Godec and Irena Paulin

Metals 2021, 11(2), 234; https://doi.org/10.3390/met11020234 - 30 Jan 2021

Cited by 7 | Viewed by 2158

Abstract

Additive manufacturing is a form of powder metallurgy, which means the properties of the initial metal powders (chemical composition, powder morphology and size) impact the final properties of the resulting parts. A complete characterization, including thermodynamic effects and the behavior of the metal powders at elevated temperatures, is crucial when planning the manufacturing process. The analysis of the Fe-Mn and Fe-Mn-Ag powder mixtures, made from pure elemental powders, shows a high susceptibility to sintering in the temperature interval from 700 to 1000 °C. Here, numerous changes to the manganese oxides and the αMn to βMn transformation occurred. The problems of mechanically mixed powders, when using selective laser melting, were highlighted by the low flowability, which led to a less controllable process, an uncontrolled arrangement of the powder and a large percentage of burnt manganese. All this was determined from the altered chemical compositions of the produced parts. The impact of the increased manganese content on the decreased probability of the transformation from γ-austenite to ε-martensite was confirmed. The ε-martensite in the microstructure increased the hardness of the material, but at the same time, its magnetic properties reduce the usefulness for medical applications. However, the produced parts had comparable elongations to human bone. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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14 pages, 21078 KiB

Open AccessArticle

Primary Recrystallization Behaviors of Hi-B Steel with Lower Initial Nitrogen Produced by the Thin Slab Casting and Rolling Process

by Bing Fu, Li Xiang, Jia-Long Qiao, Hai-Jun Wang, Jing Liu and Sheng-Tao Qiu

Metals 2021, 11(2), 189; https://doi.org/10.3390/met11020189 - 21 Jan 2021

Viewed by 1805

Abstract

Based on low-temperature high-permeability grain-oriented silicon steel designed with an initial nitrogen content of 0.0055% and produced by the thin slab casting and rolling process, the effect of total nitrogen content and nitriding temperature on primary recrystallization microstructure and texture were studied by optical microscope, scanning electron microscope, transmission electron microscope, and electron backscatter diffraction. The nitriding temperature affects the primary recrystallization behaviors significantly, while the total nitrogen content has a small effect. As the nitriding temperature is 750–850 °C, the average primary grain size and its inhomogeneity factor are about 26.58–26.67 μm and 0.568–0.572, respectively. Moreover, the texture factor is mostly between 0.15 and 0.40. Because of the relatively sufficient inhibition ability of inherent inhibitors in a decarburized sheet, the nitriding temperature (750–850 °C) affects the primary recrystallization microstructure and texture slightly. However, as the nitriding temperature rises to 900–950 °C, the average primary grain size and its inhomogeneity factor increase to 27.75–28.26 μm and 0.575–0.578, respectively. Furthermore, because of the great increase on the area fraction of {112} <110> grains, part of texture factor is increased sharply. Therefore, in order to obtain better primary grain size and homogeneity, better texture composition, and stability of the decarburized sheet, the optimal nitriding temperature is 750–850 °C. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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9 pages, 2872 KiB

Open AccessArticle

Influence of Laser Texturing on Microstructure, Surface and Corrosion Properties of Ti-6Al-4V

by Marjetka Conradi, Aleksandra Kocijan, Damjan Klobčar and Matjaž Godec

Metals 2020, 10(11), 1504; https://doi.org/10.3390/met10111504 - 11 Nov 2020

Cited by 22 | Viewed by 2636

Abstract

We present the modification of Ti-6Al-4V surfaces with a diode end-pumped Nd:YVO4 laser by varying the distance between laser-produced micro(μ)-channels. We analyzed the influence of laser texturing on the morphology, microstructure, surface and corrosion properties of Ti-6Al-4V. SEM imaging reveals a characteristic μ-channel pattern with different scan line separations, while electron backscatter diffraction (EBSD) indicates that laser texturing with the current parameters influences the microstructure up to 2 µm deep with the most significant influence at the tips, where melting and rapid solidification occur. The Vickers hardness test indicates a surface hardening effect of the laser-textured compared to the as-received Ti-6Al-4V surfaces. The XPS analysis showed that the oxide layer on the laser-textured samples was considerably thicker compared to the as-received sample, at 20 and 7 nm, respectively. We observed that the wettability was strongly correlated with the scan line separation. The results show increased hydrophobicity with increased scan line separation. The corrosion resistance was improved for laser-textured surfaces compared to the as-received surface and increased with the scan line separation. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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15 pages, 10056 KiB

Open AccessArticle

The Effect of Drawing Deformation Rate Induced Inhomogeneous Local Distortion on Phase Transformation of 304H Stainless Wire

by Qinhua Xu, Zhixian Peng, Jianxin Zhu, Mingyang Li, Yong Zong, Lei Yan, Chaoqun Li, Ke Peng, Zhaoyang Cheng and Jing Liu

Metals 2020, 10(10), 1304; https://doi.org/10.3390/met10101304 - 29 Sep 2020

Cited by 1 | Viewed by 2237

Abstract

The micro/macro magnetic properties, local element distribution, martensite transformation, and mechanical properties of 304H stainless wires are determined for two cold drawing chains. Finite element simulations are used to analyse the local strain and heat generation. The results show that there is obvious inhomogeneity in the magnetic properties, strain/stress relationship, and strain-induced heat within the drawn wires. Comparing wires with the same total strain, a larger area reduction of previous drawing processes contributes to a higher volume of the martensite phase, while a smaller area reduction of the first process results in an inhibited phase transformation. A higher single strain in the first drawing process leads to additional heat generation at the subsurface of the wire, which would eventually retard the martensite transformation. The inhomogeneous deformation-induced differences in the grain size affect the stability of austenite and transform the final martensite. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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19 pages, 6217 KiB

Open AccessArticle

Influence of the Energy Density for Selective Laser Melting on the Microstructure and Mechanical Properties of Stainless Steel

by Črtomir Donik, Jakob Kraner, Irena Paulin and Matjaž Godec

Metals 2020, 10(7), 919; https://doi.org/10.3390/met10070919 - 09 Jul 2020

Cited by 39 | Viewed by 4929

Abstract

We have investigated the impact of the process parameters for the selective laser melting (SLM) of the stainless steel AISI 316L on its microstructure and mechanical properties. Properly selected SLM process parameters produce tailored material properties, by varying the laser’s power, scanning speed and beam diameter. We produced and systematically studied a matrix of samples with different porosities, microstructures, textures and mechanical properties. We identified a combination of process parameters that resulted in materials with tensile strengths up to 711 MPa, yield strengths up to 604 MPa and an elongation up to 31%, while the highest achieved hardness was 227 HV10. The correlation between the average single-cell diameter in the hierarchical structure and the laser’s input energy is systematically studied, discussed and explained. The same energy density with different SLM process parameters result in different material properties. The higher energy density of the SLM produces larger cellular structures and crystal grains. A different energy density produces different textures with only one predominant texture component, which was revealed by electron-backscatter diffraction. Furthermore, three possible explanations for the origin of the dislocations are proposed. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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Review

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15 pages, 3068 KiB

Open AccessReview

Numerical Mesoscale Modelling of Microstructure Evolution during Selective Laser Melting

by Tijan Mede, Andraž Kocjan, Irena Paulin and Matjaž Godec

Metals 2020, 10(6), 800; https://doi.org/10.3390/met10060800 - 16 Jun 2020

Cited by 13 | Viewed by 3002

Abstract

Selective laser melting (SLM) is one of the most popular additive-manufacturing techniques that are revolutionising the production process by opening up new possibilities for unique product-shape fabrication, generating objects of complex geometry and reducing energy consumption as well as waste. However, the more widespread use of this technology is hindered by a major drawback—the thermal-history-dependent microstructure that is typical of SLM-fabricated objects is linked to uncertainties regarding the crucial material properties. While trial-and-error approaches are often employed to limit these risks, the rapidly developing field of numerical modelling represents a cheap and reliable methodology for predicting the microstructure—and by extension, the mechanical properties—of SLM-fabricated objects. Numerical approaches hitherto applied to predicting the evolution of the microstructure in SLM processes and similar boundary-value problems are reviewed and analysed in this article. The conducted analysis focused on mesoscopic scale models, which currently offer sufficient resolution to recover the key microstructural properties at a computational cost that is low enough for the methodology to be applied to industrial problems. Full article

(This article belongs to the Special Issue Microstructure-Mechanical Property Relationships in Metallic Materials)

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