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Zhang, J., Bermingham, M., Otte, J., Hou, Z., Ng, C. H., Kent, D., . . . Dargusch, M. (2025). Designing against ω phase embrittlement in additively manufactured Ti−13.5Mo metastable β titanium alloy through Sn additions. Additive Manufacturing, 97, Article ID 104597.
Open this publication in new window or tab >>Designing against ω phase embrittlement in additively manufactured Ti−13.5Mo metastable β titanium alloy through Sn additions
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2025 (English)In: Additive Manufacturing, ISSN 2214-8604, E-ISSN 2214-7810, Vol. 97, article id 104597Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing (AM) features repeated thermal cycles due to the track- and layer-wise fabrication process. However, the unique thermal cycling often encourages the precipitation of detrimental phases, such as the isothermal ω phase in metastable β titanium alloys, which cause severe embrittlement. This study aims to address ω phase embrittlement in Ti−13.5Mo (wt%) metastable β titanium alloy fabricated by laser powder bed fusion (L-PBF) through Sn additions. It is shown that 5.0 wt% Sn microparticles can be reliably in-situ alloyed with Ti−13.5Mo by L-PBF to effectively inhibit the formation of the commensurate isothermal ω phase in the binary Ti−13.5Mo alloy. Detailed microstructural characterizations and simulations of the precipitation kinetics reveal that both Ti−13.5Mo with and without Sn exhibit densely populated ω phase throughout the microstructures. However, the Sn addition retards development of the final commensurate form of isothermal ω phase, thereby mitigating its embrittling effects. As a result, Ti−13.5Mo+5Sn fabricated by L-PBF exbibits a good balance of strength and ductility which outperforms those of similar alloys produced by conventional manufacturing routines. Since the Ti−Mo binary system forms the basis of important multicomponent titanium alloys, the finding in this work is expected to be applicable beyond the binary alloy considered here and provides a framework for the design of β titanium alloys for AM that are resistant to ω phase embrittlement.

Place, publisher, year, edition, pages
Elsevier BV, 2025
Keywords
Additive manufacturing, Embrittlement, Laser powder bed fusion, Mechanical properties, Microstructure, Titanium alloys
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-358178 (URN)10.1016/j.addma.2024.104597 (DOI)001392250000001 ()2-s2.0-85212438110 (Scopus ID)
Note

QC 20250121

Available from: 2025-01-07 Created: 2025-01-07 Last updated: 2025-01-21Bibliographically approved
Zhang, J., Bermingham, M. J., Otte, J., Liu, Y., Hou, Z., Yang, N., . . . Dargusch, M. S. (2024). Ultrauniform, strong, and ductile 3D-printed titanium alloy through bifunctional alloy design. Science, 383(6683), 639-645
Open this publication in new window or tab >>Ultrauniform, strong, and ductile 3D-printed titanium alloy through bifunctional alloy design
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2024 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 383, no 6683, p. 639-645Article in journal (Refereed) Published
Abstract [en]

Coarse columnar grains and heterogeneously distributed phases commonly form in metallic alloys produced by three-dimensional (3D) printing and are often considered undesirable because they can impart nonuniform and inferior mechanical properties. We demonstrate a design strategy to unlock consistent and enhanced properties directly from 3D printing. Using Ti−5Al−5Mo−5V−3Cr as a model alloy, we show that adding molybdenum (Mo) nanoparticles promotes grain refinement during solidification and suppresses the formation of phase heterogeneities during solid-state thermal cycling. The microstructural change because of the bifunctional additive results in uniform mechanical properties and simultaneous enhancement of both strength and ductility. We demonstrate how this alloy can be modified by a single component to address unfavorable microstructures, providing a pathway to achieve desirable mechanical characteristics directly from 3D printing.

Place, publisher, year, edition, pages
American Association for the Advancement of Science (AAAS), 2024
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-343659 (URN)10.1126/science.adj0141 (DOI)38330109 (PubMedID)2-s2.0-85184935098 (Scopus ID)
Note

QC 20240222

Available from: 2024-02-22 Created: 2024-02-22 Last updated: 2024-02-22Bibliographically approved
Zhang, J., Liu, Y., Sha, G., Jin, S., Hou, Z., Bayat, M., . . . Zhang, M.-X. -. (2022). Designing against phase and property heterogeneities in additively manufactured titanium alloys. Nature Communications, 13(1), Article ID 4660.
Open this publication in new window or tab >>Designing against phase and property heterogeneities in additively manufactured titanium alloys
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2022 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 13, no 1, article id 4660Article in journal (Refereed) Published
Abstract [en]

Additive manufacturing (AM) creates digitally designed parts by successive addition of material. However, owing to intrinsic thermal cycling, metallic parts produced by AM almost inevitably suffer from spatially dependent heterogeneities in phases and mechanical properties, which may cause unpredictable service failures. Here, we demonstrate a synergistic alloy design approach to overcome this issue in titanium alloys manufactured by laser powder bed fusion. The key to our approach is in-situ alloying of Ti−6Al−4V (in weight per cent) with combined additions of pure titanium powders and iron oxide (Fe2O3) nanoparticles. This not only enables in-situ elimination of phase heterogeneity through diluting V concentration whilst introducing small amounts of Fe, but also compensates for the strength loss via oxygen solute strengthening. Our alloys achieve spatially uniform microstructures and mechanical properties which are superior to those of Ti−6Al−4V. This study may help to guide the design of other alloys, which not only overcomes the challenge inherent to the AM processes, but also takes advantage of the alloy design opportunities offered by AM.

Place, publisher, year, edition, pages
Springer Nature, 2022
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-316836 (URN)10.1038/s41467-022-32446-2 (DOI)000842289800006 ()35945248 (PubMedID)2-s2.0-85135729092 (Scopus ID)
Note

QC 20220912

Available from: 2022-09-01 Created: 2022-09-01 Last updated: 2023-03-28Bibliographically approved
Hou, Z., Babu, P. & Zhang, L. (2022). Importance of Microstructure on Precipitation in Tempering of Martensitic Steels. In: 42Nd Riso International Symposium On Materials Science: Microstructural Variability: Processing, Analysis, Mechanisms And Properties. Paper presented at 42nd Riso International Symposium on Materials Science - Microstructural Variability - Processing, Analysis, Mechanisms and Properties, SEP 05-09, 2022, Tech Univ Denmark, Dept Civil & Mech Engn, Roskilde, DENMARK. IOP Publishing, 1249, Article ID 012066.
Open this publication in new window or tab >>Importance of Microstructure on Precipitation in Tempering of Martensitic Steels
2022 (English)In: 42Nd Riso International Symposium On Materials Science: Microstructural Variability: Processing, Analysis, Mechanisms And Properties, IOP Publishing , 2022, Vol. 1249, article id 012066Conference paper, Published paper (Refereed)
Abstract [en]

Precipitation hardening is one of most effective strengthening mechanisms in steels, and much research has been performed in the past. To evaluate the contribution of precipitates, the quantitative features of precipitates including mean size and particle size distribution etc., are vital and needed. However, the predictive modeling of precipitation is still a challenge so far, especially on a quantitative level. Thus, in the present work, precipitation of carbides after tempering of martensitic FeCr-C alloys, consisting of hierarchically arranged substructures within the prioraustenite grains, namely packets and blocks of individual laths, up to 1000h has been investigated. Experimental measurements using electron microscopy and modeling using a Langer-Schwartz theory with the Kampmann-Wagner -Numerical (KWN) method have been conducted. The importance of a proper definition of the initial microstructure for predictive modeling is discussed, in terms of the comparison of calculated and experimental results.

Place, publisher, year, edition, pages
IOP Publishing, 2022
Series
IOP Conference Series-Materials Science and Engineering, ISSN 1757-8981
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-320468 (URN)10.1088/1757-899X/1249/1/012066 (DOI)000863579100065 ()
Conference
42nd Riso International Symposium on Materials Science - Microstructural Variability - Processing, Analysis, Mechanisms and Properties, SEP 05-09, 2022, Tech Univ Denmark, Dept Civil & Mech Engn, Roskilde, DENMARK
Note

QC 20221026

Available from: 2022-10-26 Created: 2022-10-26 Last updated: 2022-10-26Bibliographically approved
Zhou, T., Babu, P. R., Hou, Z. & Hedström, P. (2022). On the role of transmission electron microscopy for precipitation analysis in metallic materials. Critical reviews in solid state and materials sciences, 47(3), 388-414
Open this publication in new window or tab >>On the role of transmission electron microscopy for precipitation analysis in metallic materials
2022 (English)In: Critical reviews in solid state and materials sciences, ISSN 1040-8436, E-ISSN 1547-6561, Vol. 47, no 3, p. 388-414Article in journal (Refereed) Published
Abstract [en]

Precipitation hardening is one of the most important strengthening mechanisms in metallic materials, and thus, controlling precipitation is often critical in optimizing mechanical performance. Also other performance requirements such as functional and degradation properties are critically depending on precipitation. Control of precipitation in metallic materials is, thus, vital, and the approach presently in the limelight for this purpose is an integrated approach of theory, computations and experimental characterization. An empirical understanding is essential to build physical models upon and, furthermore, quantitative experimental data is needed to build databases and to calibrate the models. The most versatile tool for precipitation characterization is the transmission electron microscope (TEM). The TEM has sufficient resolving power to image even the finest precipitates, and with TEM-based microanalysis, overall quantitative data such as particle size distribution, volume fraction and number density of particles can be gathered. Moreover, details of precipitate structure, morphology and chemistry, can be revealed. TEM-based postmortem and in situ analysis of precipitation has made significant progress over the last decade, largely stimulated by the widespread application of aberration corrected microscopes and accompanying novel analytics. The purpose of this report is to review these recent developments in precipitation analysis methodology, including sample preparation. Application examples are provided for precipitation analysis in metals, and future prospects are discussed.

Place, publisher, year, edition, pages
Informa UK Limited, 2022
Keywords
metallic materials, phase transformation, Precipitation, precipitation hardening, transmission electron microscopy, Age hardening, High resolution transmission electron microscopy, Lime, Metals, Particle size, Particle size analysis, Transmissions, Aberration-corrected, Application examples, Experimental characterization, Integrated approach, Mechanical performance, Performance requirements, Sample preparation, Strengthening mechanisms, Metal analysis
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-310413 (URN)10.1080/10408436.2021.1941751 (DOI)000669145800001 ()2-s2.0-85109387131 (Scopus ID)
Note

QC 20250326

Available from: 2022-03-31 Created: 2022-03-31 Last updated: 2025-03-26Bibliographically approved
Deng, B., Yang, D., Wang, G., Hou, Z. & Yi, H. (2021). Effects of Austenitizing Temperature on Tensile and Impact Properties of a Martensitic Stainless Steel Containing Metastable Retained Austenite. Materials, 14(4), Article ID 1000.
Open this publication in new window or tab >>Effects of Austenitizing Temperature on Tensile and Impact Properties of a Martensitic Stainless Steel Containing Metastable Retained Austenite
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2021 (English)In: Materials, E-ISSN 1996-1944, Vol. 14, no 4, article id 1000Article in journal (Refereed) Published
Abstract [en]

Austenitizing temperature is one decisive factor for the mechanical properties of medium carbon martensitic stainless steels (MCMSSs). In the present work, the effects of austenitizing temperature (1000, 1020, 1040 and 1060 degrees C) on the microstructure and mechanical properties of MCMSSs containing metastable retained austenite (RA) were investigated by means of electron microscopy, X-ray diffraction (XRD), as well as tensile and impact toughness tests. Results suggest that the microstructure including an area fraction of undissolved M23C6, carbon and chromium content in matrix, prior austenite grain size (PAGS), fraction and composition of RA in studied MCMSSs varies with employed austenitizing temperature. By optimizing austenitizing temperature (1060 degrees C for 40 min) and tempering (250 degrees C for 30 min) heat treatments, the MCMSS demonstrates excellent mechanical properties with the ultimate tensile strength of 1740 +/- 8 MPa, a yield strength of 1237 +/- 19 MPa, total elongation (ductility) of 10.3 +/- 0.7% and impact toughness of 94.6 +/- 8.0 Jcm(-2) at room temperature. The increased ductility of alloys is mainly attributed to the RA with a suitable stability via a transformation-induced plasticity (TRIP) effect, and a matrix containing reduced carbon and chromium content. However, the impact toughness of MCMSSs largely depends on M23C6 carbides.

Place, publisher, year, edition, pages
MDPI AG, 2021
Keywords
austenitizing temperature, martensitic stainless steels, retained austenite, ductility, impact toughness, carbides
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-292310 (URN)10.3390/ma14041000 (DOI)000624118400001 ()33672618 (PubMedID)2-s2.0-85101900375 (Scopus ID)
Note

QC 20210331

Available from: 2021-03-31 Created: 2021-03-31 Last updated: 2024-07-04Bibliographically approved
Deng, B., Hou, Z., Wang, G. D. & Yi, H. L. (2021). Toughness Improvement in a Novel Martensitic Stainless Steel Achieved by Quenching–Tempering and Partitioning. Metallurgical and Materials Transactions. A, 52(11), 4852-4864
Open this publication in new window or tab >>Toughness Improvement in a Novel Martensitic Stainless Steel Achieved by Quenching–Tempering and Partitioning
2021 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 52, no 11, p. 4852-4864Article in journal (Refereed) Published
Abstract [en]

In the present work, a novel medium carbon martensitic stainless steel (MCMSS) with an excellent combination of strength, ductility, and impact toughness was designed on the basis of quenching-tempering and partitioning (Q–T&P) technology. Q–T&P is an identical heat treatment with a standard quenching and tempering (Q–T) process but has the same role with quenching and partitioning (Q&P) on microstructure control, i.e., promoting carbon-rich retained austenite via inhibiting carbide precipitation. Results show that, without compromise on strength, the total elongation and room temperature impact toughness, i.e., 9.6 pct and 90 J cm−2, of the proposed alloy (23Cr13MnSi) increase by 14 and 110 pct, respectively, as compared to those of the commercial AISI 420. The significant improvement of ductility and impact toughness in the proposed alloy is mainly a result of the gradual transformation induced plasticity (TRIP) effects, which are caused by carbon-rich retained austenite with heterogeneous stability and carbide-free martensite formed in the Q–T&P process

Place, publisher, year, edition, pages
Springer Nature, 2021
Keywords
Austenite, Carbides, Chromium alloys, Ductility, Fracture toughness, Manganese alloys, Martensite, Martensitic transformations, Quenching, Silicon alloys, Tempering, Carbide precipitation, Gradual transformations, Microstructure control, Quenching and partitioning, Quenching and tempering, Retained austenite, Temperature impact, Total elongations, Martensitic stainless steel
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:kth:diva-306078 (URN)10.1007/s11661-021-06429-9 (DOI)000694556700001 ()2-s2.0-85101914343 (Scopus ID)
Note

QC 20211221

Available from: 2021-12-21 Created: 2021-12-21 Last updated: 2022-06-25Bibliographically approved
Wang, W., Mu, W., Hou, Z., Sukenaga, S., Shibata, H., Larsson, H. & Mao, H. (2020). In-situ real time observation of martensite transformation in duplex fcc+hcp cobalt based entropic alloys. Materialia, 14, Article ID 100928.
Open this publication in new window or tab >>In-situ real time observation of martensite transformation in duplex fcc+hcp cobalt based entropic alloys
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2020 (English)In: Materialia, E-ISSN 2589-1529, Vol. 14, article id 100928Article in journal (Refereed) Published
Abstract [en]

Athermal martensite transformation in duplex fcc+hcp Co-based entropic alloys during continuous cooling was investigated in-situ. The real time observation was carried out using high temperature confocal laser scanning microscopy (HT-CLSM). This technique enables the detection of the athermal fcc to hcp transformation in entropic alloys, which is not sensitively detected by conventional thermomechanical methods e.g. dilatometer. The martensite fraction increases with increasing martensite starting temperature, and vice versa. Meanwhile, the martensite starting temperature decreases with the increasing grain size. In addition, the morphology and nucleation sites for martensite formation is discussed. This is the first time the that HT-CLSM technique is utilized in the field of entropic alloys. This in-situ observation technique coupled with thermodynamic calculations may help in the design of entropic alloys through the tailoring of the desired microstructure.

Place, publisher, year, edition, pages
Elsevier BV, 2020
Keywords
Co-based entropic alloys, Martensite transformation, In-situ observation, Confocal laser scanning microscope, Materials design
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-289036 (URN)10.1016/j.mtla.2020.100928 (DOI)000598847500010 ()2-s2.0-85094097271 (Scopus ID)
Note

QC 20210205

Available from: 2021-02-05 Created: 2021-02-05 Last updated: 2023-11-28Bibliographically approved
Hou, Z., Babu, P., Hedström, P. & Odqvist, J. (2020). On coarsening of cementite during tempering of martensitic steels. Materials Science and Technology, 36(7), 887-893
Open this publication in new window or tab >>On coarsening of cementite during tempering of martensitic steels
2020 (English)In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 36, no 7, p. 887-893Article in journal (Refereed) Published
Abstract [en]

The coarsening of cementite in a martensitic Fe–1C–1Cr (wt-%) alloy upon tempering at 700°C is investigated. When considering that the main location of cementite is at grain boundaries, classical coarsening theory can accurately predict the mean size evolution, while the predicted size distribution evolution disagrees with the experimentally observed log-normal distribution maintained throughout the whole tempering (5000 h). We conclude that classical theory of coarsening, as given by Lifshitz–Slyozov–Wagner and included in the Langer–Schwartz Kampmann–Wagner numerical approach for modelling precipitation reactions, is not fully adequate to simulate coarsening of cementite for tempering in practice.

Place, publisher, year, edition, pages
Informa UK Limited, 2020
Keywords
coarsening, Martensitic steel, particle size distribution, precipitation, tempering, Carbides, Grain boundaries, Martensitic stainless steel, Normal distribution, Ostwald ripening, Particle size, Particle size analysis, Precipitation (chemical), Size distribution, Classical theory, Log-normal distribution, Mean size, Numerical approaches, Precipitation reaction
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-277127 (URN)10.1080/02670836.2020.1740380 (DOI)000524148500001 ()2-s2.0-85082971092 (Scopus ID)
Note

QC 20200728

Available from: 2020-07-28 Created: 2020-07-28 Last updated: 2022-06-26Bibliographically approved
Zhou, T., Babu, P., Hou, Z., Odqvist, J. & Hedström, P. (2020). Precipitation of multiple carbides in martensitic CrMoV steels - experimental analysis and exploration of alloying strategy through thermodynamic calculations. Materialia, 9, Article ID UNSP 100630.
Open this publication in new window or tab >>Precipitation of multiple carbides in martensitic CrMoV steels - experimental analysis and exploration of alloying strategy through thermodynamic calculations
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2020 (English)In: Materialia, E-ISSN 2589-1529, Vol. 9, article id UNSP 100630Article in journal (Refereed) Published
Abstract [en]

Martensitic microstructures with engineered precipitation of nano-scale carbides formed during tempering are key in the development of, for example, wear-resistant steels. These steels often experience multiple carbide precipitation with evolving compositions and where the metastable phases transition to more stable carbide phases. In the case of low alloy CrMoV steels, the incomplete understanding of the complex precipitation evolution during tempering is preventing their further optimization. Therefore, in the present work we perform an in-depth experimental investigation of the precipitation of carbides in an Fe-0.32 C-1.4 Cr-0.8 Mo-0.14 V-1.1 Si-0.8 Mn-0.7 Ni (wt.%) martensitic steel tempered at 550 degrees C by transmission electron microscopy and atom probe tomography. The experimental data is compared to thermodynamic calculations and these are subsequently used to expose further potential improvements to the alloying strategy.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2020
Keywords
Precipitation, Carbides, Characterization, Thermodynamics, Materials design
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-276927 (URN)10.1016/j.mtla.2020.100630 (DOI)000537621200098 ()2-s2.0-85079660542 (Scopus ID)
Note

QC 20200622

Available from: 2020-06-22 Created: 2020-06-22 Last updated: 2023-03-28Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4825-7430

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