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Publications (10 of 44) Show all publications
Vuorinen, E., Gülfem Özügürler, A., Ion, J., Eriksson, K., Chandra Somani, M., Pentti Karjalainen, L., . . . Garcia Caballero, F. (2019). Hot Forming of Ultra-Fine-Grained Multiphase Steel Products Using Press Hardening Combined with Quenching and Partitioning Process. Metals, 9(3), Article ID 357.
Open this publication in new window or tab >>Hot Forming of Ultra-Fine-Grained Multiphase Steel Products Using Press Hardening Combined with Quenching and Partitioning Process
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2019 (English)In: Metals, ISSN 2075-4701, Vol. 9, no 3, article id 357Article in journal (Refereed) Published
Abstract [en]

Hot forming combined with austempering and quenching and partitioning (QP) processes have been used to shape two cold rolled high silicon steel sheets into hat profiles. Thermal simulation on a Gleeble instrument was employed to optimize processing variables to achieve an optimum combination of strength and ductility in the final parts. Microstructures were characterized using optical and scanning electron microscopy and X-ray diffraction. Tensile strengths (Rm) of 1190 and 1350 MPa and elongations to fracture (A50mm) of 8.5 and 7.4%, were achieved for the two high-silicon steels having 0.15 and 0.26 wt % C, respectively. Preliminary results show that press hardening together with a QP heat treatment is an effective method of producing components with high strength and reasonable tensile ductility from low carbon containing steels that have the potential for carbide free bainite formation. The QP treatment resulted in faster austenite decomposition during partitioning in the steels in comparison with an austempering treatment.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
hot forming, multiphase steel, quenching and partitioning, austempering, Gleeble simulation, press hardening
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-73787 (URN)10.3390/met9030357 (DOI)000464321200008 ()2-s2.0-85064219072 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-04-30 (johcin)

Available from: 2019-04-30 Created: 2019-04-30 Last updated: 2019-04-30Bibliographically approved
Forouzan, F., Borasi, L., Vuorinen, E. & Mücklich, F. (2019). Optimization of Quenching Temperature to Minimize the Micro Segregation Induced Banding Phenomena in Quenching and Partitioning (Q&P) Steels. Steel Research International, 90(1), Article ID 1800281.
Open this publication in new window or tab >>Optimization of Quenching Temperature to Minimize the Micro Segregation Induced Banding Phenomena in Quenching and Partitioning (Q&P) Steels
2019 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 90, no 1, article id 1800281Article in journal (Refereed) Published
Abstract [en]

Mn, Cr, and Si are favorable elements for designing the quenching and partitioning (Q&P) steels while the microsegregation of them is a common phenomenon in the steels. This segregation makes the bands of enriched and depleted Mn–Cr regions, which affects the Ms temperature of the bands and consequently influence the volume fraction of initial martensite, retained austenite, and secondary fresh martensite in different bands. This issue leads to non-homogeneity in the microstructure and mechanical properties. In this study, the optimization method to minimize the inhomogeneity by selection of the quenching temperature is demonstrated.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
banding, hardness, microsegregation, microstructure, quenching and partitioning (Q&P)
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71024 (URN)10.1002/srin.201800281 (DOI)000454790200006 ()2-s2.0-85053542723 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-01-25 (johcin) 

Available from: 2018-09-28 Created: 2018-09-28 Last updated: 2019-03-04Bibliographically approved
Forouzan, F., Borasi, L., Vuorinen, E. & Mücklich, F. (2019). Process Control Maps to Design an Ultra-High Strength-Ductile Steel. Materials Science and Technology, 35(10), 1173-1184
Open this publication in new window or tab >>Process Control Maps to Design an Ultra-High Strength-Ductile Steel
2019 (English)In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 35, no 10, p. 1173-1184Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
ultrahigh strength, high carbon low alloy steel, Q&P, ductility, map
National Category
Metallurgy and Metallic Materials Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-73102 (URN)10.1080/02670836.2019.1615752 (DOI)000469142200001 ()2-s2.0-85066881284 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-06-19 (johcin)

Available from: 2019-03-04 Created: 2019-03-04 Last updated: 2019-06-19Bibliographically approved
Moghaddam, P. V., Hardell, J., Vuorinen, E. & Prakash, B. (2019). The role of retained austenite in dry rolling/sliding wear of nanostructured carbide-free bainitic steels. Wear, 428-429, 193-204
Open this publication in new window or tab >>The role of retained austenite in dry rolling/sliding wear of nanostructured carbide-free bainitic steels
2019 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 428-429, p. 193-204Article in journal (Refereed) Published
Abstract [en]

The dry rolling/sliding wear of nanostructured bainite has been investigated and compared with that of a conventional quenched and tempered bearing steel. In order to elucidate the role of retained austenite on the wear performance, high silicon hypereutectoid bearing steel with an identical alloy composition was heat treated to obtain different microstructures with similar hardness and different amounts of retained austenite. The results indicate that the nanostructured bainite can meet the minimum hardness requirements for bearing applications. Moreover, the nanostructured bainite outperformed the tempered martensitic steel in terms of wear resistance. The work hardening capacity and thus wear resistance increases due to the transformation of retained austenite into martensite. The results of XRD analyses show that the higher stability of retained austenite and strength of bainitic ferrite leads to better wear performance. It is demonstrated that the stability of retained austenite outweigh the influence of retained austenite content on wear resistance. Adhesion and oxidation were identified as the main wear mechanisms. In addition to microstructure, surface oxidation also plays a prominent role in determining the wear resistance. 

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Bearings, Carbide-free bainite, Nanostructured materials, Retained austenite, Rolling-sliding, TRIP effect
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Research subject
Machine Elements
Identifiers
urn:nbn:se:ltu:diva-73366 (URN)10.1016/j.wear.2019.03.012 (DOI)000471596300019 ()2-s2.0-85063237323 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-04-01 (svasva)

Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-07-10Bibliographically approved
Forouzan, F., Guitar, M. A., Vuorinen, E. & Mücklich, F. (2018). Effect of Carbon Partitioning, Carbide Precipitation, and Grain Size on Brittle Fracture of Ultra-High-Strength, Low-Carbon Steel after Welding by a Quenching and Partitioning Process. Metals, 8(10), Article ID 747.
Open this publication in new window or tab >>Effect of Carbon Partitioning, Carbide Precipitation, and Grain Size on Brittle Fracture of Ultra-High-Strength, Low-Carbon Steel after Welding by a Quenching and Partitioning Process
2018 (English)In: Metals, ISSN 2075-4701, Vol. 8, no 10, article id 747Article in journal (Refereed) Published
Abstract [en]

To improve the weld zone properties of Advanced High Strength Steel (AHSS), quenching and partitioning (Q&P) has been used immediately after laser welding of a low-carbon steel. However, the mechanical properties can be affected for several reasons: (i) The carbon content and amount of retained austenite, bainite, and fresh martensite; (ii) Precipitate size and distribution; (iii) Grain size. In this work, carbon movements during the partitioning stage and prediction of Ti (C, N), and MoC precipitation at different partitioning temperatures have been simulated by using Thermocalc, Dictra, and TC-PRISMA. Verification and comparison of the experimental results were performed by optical microscopy, X-ray diffraction (XRD), Scanning Electron Microscop (SEM), and Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Scanning Diffraction (EBSD) analysis were used to investigate the effect of martensitic/bainitic packet size. Results show that the increase in the number density of small precipitates in the sample partitioned at 640 °C compensates for the increase in crystallographic packets size. The strength and ductility values are kept at a high level, but the impact toughness will decrease considerably.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
low-carbon AHSS, Q&P, toughness, modelling, precipitation, martensite packet
National Category
Metallurgy and Metallic Materials Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-71070 (URN)10.3390/met8100747 (DOI)2-s2.0-85053830157 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-10-05 (svasva)

Available from: 2018-10-02 Created: 2018-10-02 Last updated: 2019-03-04Bibliographically approved
Forouzan, F., Strandqvist, N., Vuorinen, E., Navara, E. & Mücklich, F. (2017). Effect of tempering on microstructure and mechanical properties of laser welded and post-weld treated AHSS specimens. Paper presented at 16th International Symposium on Metallography and Materials Science, Stará Lesná, High Tatra Mountains, Slovak Republic, April 20-22, 2016. Materials Science Forum, 891, 18-24
Open this publication in new window or tab >>Effect of tempering on microstructure and mechanical properties of laser welded and post-weld treated AHSS specimens
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2017 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 891, p. 18-24Article in journal (Refereed) Published
Abstract [en]

An advanced high strength steel (0.08 wt.%C, 1.79 wt%Mn, 0.23 wt%Si) was subjected to different post-weld heat treatments by quenching & tempering treatments (Q&T) after laser welding to reduce the risk of martensite formation in a few seconds based on an idea of quench and partitioning (Q&P), mechanism. The thermal stability of retained austenite, microstructure development and mechanical properties have been studied at 2 tempering temperatures of 440°C (Ms) and 636°C (Bs), both for 15 minutes, by means of electron microscopy, dilatometry, hardness profile and tensile tests. Dilatometer study unveiled that redistribution of carbon atoms and precipitation of transition carbides occur around 150°C and austenite decomposition occur at 600°C. Tempering at 636°C resulted in notable effect on the mechanical properties, while no significant difference was detected at 440°C, except a slight hardness drop. The strength increased up to 12% for the different specimens without significant loss in ductility for all specimens tempered at 636°C, which may be caused by precipitation hardening and recrystallization of martensite lath boundaries during tempering around 600°C.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2017
Keywords
laser welding, quench and temper (Q&T), dilatometer, hardness profile, tensile test
National Category
Metallurgy and Metallic Materials
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-62255 (URN)10.4028/www.scientific.net/MSF.891.18 (DOI)2-s2.0-85016978363 (Scopus ID)
Conference
16th International Symposium on Metallography and Materials Science, Stará Lesná, High Tatra Mountains, Slovak Republic, April 20-22, 2016
Note

Konferensartikel i tidskrift; 2017-03-15 (andbra)

Available from: 2017-03-02 Created: 2017-03-02 Last updated: 2019-04-03Bibliographically approved
Pineda Huitron, R. M. & Vuorinen, E. (2017). Hot cracking of Structural Steel during Laser Welding. Paper presented at International Materials Research Meeting in the Greater Region: "Current Trends in the Characterisation of Materials and Surface Modification", Saarland University, Saarbrücken, Germany, 6–7 April 2017. IOP Conference Series: Materials Science and Engineering, 258, Article ID 012005.
Open this publication in new window or tab >>Hot cracking of Structural Steel during Laser Welding
2017 (English)In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 258, article id 012005Article in journal (Refereed) Published
Abstract [en]

Laser welding is an important technique in many industries due to its high precision in operation, its local and fast processing, narrow welds and its good weld surface quality. However, the process can involve some complications due to the rapid heating and cooling of the material processed, resulting in physical and metallurgical effects as thermal contraction during solidification, giving as a result the presence of residual stresses in the narrow weld. Formation of defects during the process is an important topic to be evaluated in order to achieve better performance of the steels in use. In the present work, defects formed during laser welding of a structural steel have been investigated. The defects formed have been identified and the causes of the defects are discussed. Possible strategies for improvement of the welding procedure and final weld result are proposed. The defects were analysed by optical and scanning electron microscopy and hardness measurement. Cracks were located in the middle of the fusion zone and followed both inter-granular and trans-granular paths. Impurities as manganese sulphides were found along the welding direction, and could act as sites for crack formation. The cracks formed during solidification of the weld are identified as solidification cracks. This kind of cracks is usually caused by solidification shrinkage and thermal contractions during the process, which appear in the fusion zone and sometimes in the heat affected zone.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-66339 (URN)10.1088/1757-899X/258/1/012005 (DOI)2-s2.0-85035080802 (Scopus ID)
Conference
International Materials Research Meeting in the Greater Region: "Current Trends in the Characterisation of Materials and Surface Modification", Saarland University, Saarbrücken, Germany, 6–7 April 2017
Note

Konferensartikel i tidskrift

Available from: 2017-11-01 Created: 2017-11-01 Last updated: 2018-03-05Bibliographically approved
Forouzan, F., Gunasekaran, S., Hedayati, A., Vuorinen, E. & Mücklich, F. (2017). Microstructure analysis and mechanical properties of Low alloy High strength Quenched and Partitioned Steel. Paper presented at 8th conference of Materials Structure & Micromechanics of Fracture (MSMF8), Brno, Czech republic, 27-29 June, 2016. Solid State Phenomena, 258, 574-578
Open this publication in new window or tab >>Microstructure analysis and mechanical properties of Low alloy High strength Quenched and Partitioned Steel
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2017 (English)In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 258, p. 574-578Article in journal (Refereed) Published
Abstract [en]

Gleeble study of the quenching and partitioning (Q&P) process has been performed onDomex 960 steel (Fe, 0.08 %C, 1.79 %Mn, 0.23 %Si, 0.184 %Ti, and 0.038 %Al). The effect ofdifferent Q&P conditions on microstructure and mechanical properties were investigated. The aimof the process is to produce a fine grained microstructure for better ductility and controlled amountsof different micro-constituents to increase the strength and toughness simultaneously. Threedifferent quenching temperatures, three partitioning temperatures and three partitioning times havebeen selected to process the 27 specimens by Gleeble® 1500. The specimens were characterized bymeans of OM, SEM, XRD, hardness and impact tests. It was found that, fine lath martensite withretained austenite is achievable without high amount of Si or Al in the composition although lack ofthese elements may cause the formation of carbides and decrease the available amount of carbon forpartitioning into the austenite. The hardness increases as the quenching temperature is decreased,however, at highest partitioning temperature (640◦C) the hardness increases sharply due to extensiveprecipitate formation.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2017
Keywords
AHSS, Gleeble, Quenching and partitioning (Q&P), X-ray, mechanical properties
National Category
Other Materials Engineering
Research subject
Engineering Materials; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-60479 (URN)10.4028/www.scientific.net/SSP.258.574 (DOI)2-s2.0-85009754153 (Scopus ID)
Conference
8th conference of Materials Structure & Micromechanics of Fracture (MSMF8), Brno, Czech republic, 27-29 June, 2016
Note

Konferensartikel i tidskrift

Available from: 2016-11-16 Created: 2016-11-16 Last updated: 2019-03-04Bibliographically approved
Forouzan, F., Vuorinen, E. & Mücklich, F. (2017). Post weld-treatment of laser welded AHSS by application of quenching and partitioning technique. Materials Science & Engineering: A, 698, 174-182
Open this publication in new window or tab >>Post weld-treatment of laser welded AHSS by application of quenching and partitioning technique
2017 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 698, p. 174-182Article in journal (Refereed) Published
Abstract [en]

Two-step quenching and partitioning (Q&P) treatment was applied on specimens of an advanced high strength steel (AHSS) after laser welding, for post welding treatment. In order to avoid formation of brittle martensite phase, which usually form due to very high cooling rate of laser welding. To simulate the effect of different Q&P parameters after welding in the most critical part of HAZ, several cycles were performed in Gleeble simulator and analyzed in advance. Subsequently some of the cycles were repeated after laser welding by using an induction heater close to the weld. Different techniques including SEM, EBSD and XRD were used to analyze the microconstituents of the structure and mechanical properties were investigated by micro-hardness measurements across the weld, tensile and impact toughness tests. The final structure consists of controlled amount of tempered martensite with precipitates, bainite laths and small amount of fresh martensite depending on the thermal cycles. In addition, samples heated at a temperature between Ms and Bs (in this case 540C) showed the best mechanical properties. Therefore, this technique not only improves the microstructure and mechanical properties of the fusion zone (FZ) and heat affected zone (HAZ) but gives also a quick industrial processing method for post welding treatments.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
AHSS, Quenching and partitioning, Microstructure, Mechanical properties
National Category
Metallurgy and Metallic Materials Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-63370 (URN)10.1016/j.msea.2017.05.053 (DOI)000405251900021 ()2-s2.0-85019392617 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-05-24 (andbra)

Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2019-09-13Bibliographically approved
Forouzan, F., Zhang, H., Vuorinen, E. & Mücklich, F. (2017). Study of The Kinetics of Precipitation in an AHSS steel after Laser Welding and Quenching and Partitioning. In: : . Paper presented at International Materials Research Meeting In The Greater Region, Saarbrücken, 6-7 April 2017.
Open this publication in new window or tab >>Study of The Kinetics of Precipitation in an AHSS steel after Laser Welding and Quenching and Partitioning
2017 (English)Conference paper, Oral presentation with published abstract (Other academic)
National Category
Metallurgy and Metallic Materials Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-63375 (URN)
Conference
International Materials Research Meeting In The Greater Region, Saarbrücken, 6-7 April 2017
Available from: 2017-05-17 Created: 2017-05-17 Last updated: 2018-06-14Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9100-7982

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