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Asala, G., Andersson, J. & Ojo, O. A. (2019). A study of the dynamic impact behaviour of IN 718 and ATI 718Plus® superalloys. Philosophical Magazine, 99(4), 419-437
Open this publication in new window or tab >>A study of the dynamic impact behaviour of IN 718 and ATI 718Plus® superalloys
2019 (English)In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 99, no 4, p. 419-437Article in journal (Refereed) Published
Abstract [en]

The dynamic impact response of IN 718 and ATI 718Plus®, in both the solution heat treated and age-hardened conditions, were investigated at different deformation temperatures and strain rates using a direct impact Hopkinson pressure bar. Analyses of the results provide a vital but previously not reported information that the ATI 718Plus® offers a higher resistance to damage during high strain rate ballistic impact deformation compared to the most widely used Iron-nickel based superalloy, Inconel 718. ATI 718Plus® showed higher strain hardening and strain rate sensitivity, in both heat treatment conditions, than IN 718. The difference in the deformation behaviour of both alloys, in the annealed condition, is attributable to the compositional modification in ATI 718Plus® which has been reported to lower its stacking fault energy and increases the tendency for deformation twinning. However, in the age-hardened condition, the difference is believed to be related to the disparity in the operative strengthening mechanism, of the precipitates present in both alloys. Furthermore, a higher susceptibility to strain location and the formation of adiabatic shear band, in aged IN 718, is attributable to the stronger temperature-softening characteristics observed in the alloy and to the limited strain hardening tendency under dynamic impact loading. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

Place, publisher, year, edition, pages
Taylor and Francis Ltd., 2019
Keywords
Deformation, Dynamics, Iron alloys, Mechanical properties, Nickel alloys, Scanning electron microscopy, Shear bands, Strain hardening, Superalloys, Transmission electron microscopy, Twinning, Compositional modification, Damage, Deformation properties, Deformation temperatures, Heat treatment conditions, Stacking fault energies, Strain hardening and strain rate sensitivity, Strengthening mechanisms, Strain rate
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13177 (URN)10.1080/14786435.2018.1540891 (DOI)000455480300002 ()2-s2.0-85056162234 (Scopus ID)
Note

Published online: 07 Nov 2018

Funder: Natural Sciences and Engineering Research Council of Canada

Available from: 2018-12-03 Created: 2018-12-03 Last updated: 2019-02-04Bibliographically approved
Asala, G., Andersson, J. & Ojo, O. A. (2019). Analysis and constitutive modelling of high strain rate deformation behaviour of wire-arc additive-manufactured ATI 718Plus superalloy. The International Journal of Advanced Manufacturing Technology, 3(1-4), 1419-1431
Open this publication in new window or tab >>Analysis and constitutive modelling of high strain rate deformation behaviour of wire-arc additive-manufactured ATI 718Plus superalloy
2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 3, no 1-4, p. 1419-1431Article in journal (Refereed) Epub ahead of print
Abstract [en]

A fundamental prerequisite for obtaining realistic finite element simulation of machining processes, which has become a key machinability assessment for metals and alloys, is the establishment of a reliable material model. To obtain the constitutive model for wire-arc additive-manufactured ATI 718Plus, Hopkinson pressure bar is used to characterise the flow stress of the alloy over a wide range of temperatures and strain rates. Experiment results show that the deformation behaviours of as-deposited ATI 718Plus superalloy are influenced by the applied strain rate, test temperature and strain. Post-deformation microstructures show localised deformation within the deposit, which is attributable to the heterogeneous distribution of the strengthening precipitates in as-deposited ATI 718Plus. Furthermore, cracks are observed to be preferentially initiated at the brittle eutectic solidification constituents within the localised band. Constitutive models, based on the strain-compensated Arrhenius-type model and the modified Johnson-Cook model, are developed for the deposit based on experimental data. Standard statistical parameters, correlation coefficient (R), root-mean-square error (RMSE) and average absolute relative error (AARE) are used to assess the reliability of the models. The results show that the modified Johnson-Cook model has better reliability in predicting the dynamic flow stress of wire-arc-deposited ATI 718Plus superalloy. © 2019, Springer-Verlag London Ltd., part of Springer Nature.

Keywords
3D printers, Additives, Constitutive models, Deformation, Deposits, Machinability, Machining, Mean square error, Metallurgy, Nickel alloys, Plastic flow, Solidification, Superalloys, Wire, Deformation microstructure, Finite element simulations, Heterogeneous distributions, High strain rate deformation, High strain rates, Machinability assessment, Ni-based superalloys, Root mean square errors, Strain rate
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13848 (URN)10.1007/s00170-019-03616-2 (DOI)2-s2.0-85064476747 (Scopus ID)
Note

First Online: 05 April 2019

Funders; Natural Sciences and Engineering Research Council of Canada

Available from: 2019-05-24 Created: 2019-05-24 Last updated: 2019-07-26Bibliographically approved
Karimi Neghlani, P., Sadeghi, E., Ålgårdh, J. & Andersson, J. (2019). EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics. Materials Characterization, 148, 88-99
Open this publication in new window or tab >>EBM-manufactured single tracks of Alloy 718: Influence of energy input and focus offset on geometrical and microstructural characteristics
2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 148, p. 88-99Article in journal (Refereed) Published
Abstract [en]

Electron beam melting-powder bed fusion (EBM-PBF) is an additive manufacturing process, which is able to produce parts in layer-by-layer fashion from a 3D model data. Currently application of this technology in parts manufacturing with high geometrical complexity has acquired growing interest in industry. To recommend the EBM process into industry for manufacturing parts, improved mechanical properties of final part must be obtained. Such properties highly depend on individual single melted track and single layer. In EBM, interactions between the electron beam, powder, and solid underlying layer affect the geometrical (e.g., re-melt depth, track width, contact angle, and track height) and microstructural (e.g., grain structure, and primary dendrite arm spacing) characteristics of the melted tracks. The core of the present research was to explore the influence of linear energy input parameters in terms of beam scanning speed, beam current as well as focus offset and their interactions on the geometry and microstructure of EBM-manufactured single tracks of Alloy 718. Increased scanning speed led to lower linear energy input values (<0.9 J/mm) in an specific range of the focus offset (0–10 mA) which resulted in instability, and discontinuity of the single tracks as well as balling effect. Decreasing the scanning speed and increasing the beam current resulted in higher melt pool depth and width. By statistical evaluations, the most influencing parameters on the geometrical features were primarily the scanning speed, and secondly the beam current. Primary dendrite arm spacing (PDAS) slightly decreased by increasing the scanning speed using lower beam current values as the linear energy input decreased. By increasing the linear energy input, the chance of more equiaxed grain formation was high, however, at lower linear energy input, mainly columnar grains were observed. The lower focus offset values resulted in more uniform grains along the 〈001〉 crystallographic direction. © 2018 Elsevier Inc. 

Keywords
3D printers; Contact angle; Dendrites (metallography); Design of experiments; Electron beam melting; Electron beams; Scanning; Speed, Alloy 718; Geometrical characteristics; Powder bed; Single-tracks; Solidified microstructures, Geometry
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13365 (URN)10.1016/j.matchar.2018.11.033 (DOI)2-s2.0-85058512738 (Scopus ID)
Funder
European Regional Development Fund (ERDF)Knowledge Foundation
Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-02-28Bibliographically approved
Sadeghi, E., Karimi Neghlani, P., Momeni, S., Seifi, M., Eklund, A. & Andersson, J. (2019). Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718. Materials Characterization, 150, 236-251
Open this publication in new window or tab >>Influence of thermal post treatments on microstructure and oxidation behavior of EB-PBF manufactured Alloy 718
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2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 150, p. 236-251Article in journal (Refereed) Published
Abstract [en]

The effect of thermal post treatments consisting of heat treatment (HT), hot isostatic pressing (HIP), and combined HIP-HT on microstructure and oxidation behavior of Alloy 718 manufactured by electron beam powder bed fusion (EB-PBF) technique was investigated. Oxidation of the as-built and post-treated specimens was performed in ambient air at 650, 750, and 850 °C for up to 168 h. Directional columnar-grained microstructure, pores and fine Nb-rich carbides were observed in the as-built specimen. The HT specimen presented the columnar microstructure, plate-like δ phase at grain boundaries, and pores. The dominant grain crystallographic orientation was changed from 〈001〉 in the as-built specimen to 〈101〉 after HT. No grain boundary δ phase was observed in the HIPed specimen, but recrystallization occurred in both the HIP and HIP-HT specimens due to a rapid cooling after HIPing motivating the nucleation of fine grains with limited time to grow. After oxidation exposure at 650 and 750 °C for 168 h, no big difference between weight changes of the as-built and post-treated specimens was noted, whereas at 850 °C, the combined HIP-HT specimen showed the most promising corrosion resistance with the least weight change. At 850 °C, a protective scale of Cr 2 O 3 rich in Cr, Ti, and Ni as well as an internal oxide (branched structure of alumina) developed in all the specimens, while, only a protective Cr 2 O 3 scale was found at 650 and 750 °C. The HIP-HT specimen at 850 °C developed an oxide scale, which was denser and more adherent in comparison to the oxide scales formed on the other three specimens, associated with its limited defect distribution and more homogenized microstructure. Moreover, the δ phase formed close to the surface of the exposed specimens during the oxidation exposure at 850 °C most probably led to nucleation and growth of the oxide scale. © 2019 Elsevier Inc.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Additive manufacturing, Electron beam powder bed fusion, Alloy 718, Oxidation, Heat treatment, Hot isostatic pressing
National Category
Manufacturing, Surface and Joining Technology Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13740 (URN)10.1016/j.matchar.2019.02.016 (DOI)000462420900027 ()2-s2.0-85062014143 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-05-10Bibliographically approved
Singh, S. & Andersson, J. (2019). Varestraint weldability testing of cast ATI® 718Plus™: a comparison to cast Alloy 718. Welding in the World, 63(2), 389-399
Open this publication in new window or tab >>Varestraint weldability testing of cast ATI® 718Plus™: a comparison to cast Alloy 718
2019 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 63, no 2, p. 389-399Article in journal (Refereed) Published
Abstract [en]

Varestraint testing of the newly developed cast ATI® 718Plus™ after pseudo-HIP (hot isostatic pressing) heat treatments showed that the extent of solidification cracking was independent of the heat treatment condition. The susceptibility towards heat-affected zone (HAZ) liquation cracking was found to be related to the heat treatment dwell time rather than the temperature. The heat treatments at 1120 and 1190 °C for 24 h were the most susceptible to cracking. On the other hand, heat treatments at 1120, 1160 and 1190 °C for 4-h dwell time exhibited the least amount of cracking. The solidification cracking was found to be similar whereas the HAZ liquation cracking was lower for ATI® 718Plus™ after the heat treatment at 1120 and 1190 °C for 4-h dwell time in comparison to cast Alloy 718.

Keywords
Hot cracking, Cast ATI® 718Plus™, Cast alloy 718, Varestraint testing, Backfilling
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13843 (URN)10.1007/s40194-018-0626-2 (DOI)000462318600015 ()2-s2.0-85063279429 (Scopus ID)
Funder
Swedish Energy Agency
Note

Funders: GKN Aerospace Sweden AB 

Available from: 2019-05-24 Created: 2019-05-24 Last updated: 2019-07-25Bibliographically approved
Haas, S., Andersson, J., Fisk, M., Park, J.-S. & Lienert, U. (2018). Correlation of precipitate evolution with Vickers hardness in Haynes® 282® superalloy: In-situ high-energy SAXS/WAXS investigation. Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, 11, 250-258
Open this publication in new window or tab >>Correlation of precipitate evolution with Vickers hardness in Haynes® 282® superalloy: In-situ high-energy SAXS/WAXS investigation
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2018 (English)In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 11, p. 250-258Article in journal (Refereed) Published
Abstract [en]

The aim of this work is to characterize the precipitation kinetics in Haynes® 282® superalloys using in-situ high-energy Small Angle X-ray Scattering (SAXS) together with Wide Angle X-ray Scattering (WAXS). The phases identified by WAXS include γ (matrix), γ′ (hardening precipitates), MC (metallic carbides), and M23C6/M6C (secondary metallic carbides). The γ'-precipitates are spheroids with a diameter of several nanometres, depending on the temperature and ageing time. From the SAXS data, quantitative parameters such as volume fraction, number density and inter-particle distance were determined and correlated with ex-situ Vickers microhardness measurements. The strengthening components associated with precipitates and solid solutions are differentiated using the measured Vickers microhardness and SAXS model parameters. A square root dependence between strengthening attributable to the precipitates and the product of volume fraction and mean precipitate radius is found. The solid solution strengthening component correlates with the total volume fraction of precipitates.

Keywords
X-ray analysis, characterization, hardness, nickel alloys, SAXS, WAXS
National Category
Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-11877 (URN)10.1016/j.msea.2017.11.035 (DOI)000423246600027 ()2-s2.0-85034657372 (Scopus ID)
Funder
VINNOVA, 2014-06041
Note

Swedish National Aviation Engineering Research Programme (2015-02285); SSF-project Additive Manufacturing - Development of Process and Materials (GMT14-0048);  U.S. DOE no. DEAC02-06CH11357 

Available from: 2017-12-04 Created: 2017-12-04 Last updated: 2019-02-05Bibliographically approved
Segerstark, A., Andersson, J., Svensson, L.-E. & Ojo, O. (2018). Effect of Process Parameters on the Crack Formation in Laser Metal Powder Deposition of Alloy 718. Metallurgical and Materials Transactions. A, 49A(10), 5042-5050
Open this publication in new window or tab >>Effect of Process Parameters on the Crack Formation in Laser Metal Powder Deposition of Alloy 718
2018 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 49A, no 10, p. 5042-5050Article in journal (Refereed) Published
Abstract [en]

Cracking in Alloy 718 using laser metal powder deposition has been evaluated in this study. It is found that the material is susceptible to cracking when the laser power is high, the scanning speed is high and the powder feeding rate is low. Almost all the cracks are located close to the center of the deposited wall and propagates in the normal direction to the substrate. Evidence of liquation are found at the cracked surfaces and since all cracks reside in regions which are reheated several times, the cracks are determined to mostlikely be heat affected zone liquation cracks. The influence of respective process parameter was evaluated using a design of experiment approach. It is shown that, when the powder feeding rate is incorporated as avariable, the heat input is not a suitable indicator for the hot cracking susceptibility in laser metal powder deposition of Alloy 718. A combinatory model using the power ratio together with the heat input is therefore proposed.

Keywords
Laser Metal Deposition, Additive manufacturing, Powder, Superalloy, Cracking, Characterization
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-11841 (URN)10.1007/s11661-018-4767-0 (DOI)000443469700064 ()2-s2.0-85049122881 (Scopus ID)
Funder
Region Västra GötalandSwedish Agency for Economic and Regional Growth
Note

Ingår i avhandling och det finns ett tidigare publicerat manuskript.

Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2019-03-05Bibliographically approved
Singh, S. & Andersson, J. (2018). Hot cracking in cast alloy 718. Science and technology of welding and joining, 23(7), 568-574
Open this publication in new window or tab >>Hot cracking in cast alloy 718
2018 (English)In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 23, no 7, p. 568-574Article in journal (Refereed) Published
Abstract [en]

Hot cracking susceptibility of the Fe–Ni-based precipitation hardening cast superalloy Alloy 718 was studied by Varestraint weldability testing. The effect of two hot isostatic pressing (HIP) treatments commonly employed in the aerospace industry was investigated in reference to the as cast condition. It was found that the heat affected zone (HAZ) liquation cracking susceptibility increased for samples with pre-weld HIP treatments. The as cast condition disclosed the best response for liquation cracking followed by HIP-1120 (1120°C/4h (HIP) + 1050°C/1h and furnace cooling to 650°C/1h in vacuum + 950°C/1h) and HIP-1190 (1190°C/4h (HIP) + 870°C/10h and furnace cooling to 650°C/1h in vacuum + 950°C/1h). The amount of the secondary precipitates and base metal grain size was found to be important parameters influencing the cracking susceptibility. Regarding solidification cracking susceptibility, the three conditions appear to behave similarly. © 2018 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute.

Keywords
Aerospace industry; Age hardening; Cracks; Electric arc welding; Heat affected zone; Precipitation (chemical); Sintering; Solidification; Vacuum furnaces, Alloy 718; Cracking susceptibility; Furnace cooling; Hot cracking; Liquation cracking; Secondary precipitates; Solidification cracking; Solidification cracking susceptibility, Hot isostatic pressing
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-12133 (URN)10.1080/13621718.2018.1429238 (DOI)000440719100004 ()2-s2.0-85041239440 (Scopus ID)
Funder
Swedish Energy Agency
Note

Published online: 30 Jan 2018

Available from: 2018-02-20 Created: 2018-02-20 Last updated: 2019-05-27Bibliographically approved
Manitsas, D. & Andersson, J. (2018). Hot Cracking Mechanisms in Welding Metallurgy: A Review of Theoretical Approaches. Paper presented at 5th International Conference of Engineering Against Failure, ICEAF-V 2018, 20 June 2018 through 22 June 2018. MATEC Web of conferences, 188, Article ID 03018.
Open this publication in new window or tab >>Hot Cracking Mechanisms in Welding Metallurgy: A Review of Theoretical Approaches
2018 (English)In: MATEC Web of conferences, E-ISSN 2261-236X, Vol. 188, article id 03018Article in journal (Refereed) Published
Abstract [en]

Hot cracking often refers to the appearance of liquid films along grain boundaries or to another place in the weld metal structure. Despite hot cracking importance in alloy weldability, there is limited understanding of the influencing mechanisms. Theories and criteria worked out over the years to assess alloy weldability will be presented. The review focuses on: 1) Theories of hot cracking, 2) Hot cracking criteria, and 3) A criticism of hot cracking theories and criteria.

Place, publisher, year, edition, pages
EDP Sciences, 2018
Keywords
Grain boundaries, Liquid films, Weldability, Hot cracking, Influencing mechanisms, Of liquid films, Theoretical approach, Weld metal, Welding metallurgy, Electric arc welding
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12976 (URN)10.1051/matecconf/201818803018 (DOI)2-s2.0-85053214148 (Scopus ID)
Conference
5th International Conference of Engineering Against Failure, ICEAF-V 2018, 20 June 2018 through 22 June 2018
Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2019-05-29Bibliographically approved
Asala, G., Andersson, J. & Ojo, O. A. (2018). Improved dynamic impact behaviour of wire-arc additive manufactured ATI 718Plus®. Materials Science & Engineering: A, 738, 111-124
Open this publication in new window or tab >>Improved dynamic impact behaviour of wire-arc additive manufactured ATI 718Plus®
2018 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 738, p. 111-124Article in journal (Refereed) Published
Abstract [en]

The dynamic response and impact resistance of wire-arc additive manufactured (AMed) and wrought ATI 718Plus in different heat treatment conditions are characterised by using a direct impact Hopkinson pressure bar system. In addition, microstructural analyses of the alloys, before and after impact, are characterised by using advanced microscopy techniques, including scanning electron and transmission electron microscopies. The experimental results show that the impact resistance of the AMed alloy in the as-processed condition is inferior to that of the wrought alloy. The lower impact resistance is attributed to the presence of eutectic solidification constituents in the interdendritic regions and to the inhomogeneous distribution of the strengthening precipitates in the deposit. After the application of the recommended heat treatment for ATI 718Plus, excessive formation of η-phase particles are observed in the microstructure in addition to Laves phase particles. Since the recommended heat treatment for ATI 718Plus is not sufficient to eliminate the deleterious phases and optimise the properties of the alloy, a novel heat treatment procedure is proposed. Dynamic impact study of the AMed alloy after the application of the proposed approach shows that the alloy exhibits a dynamic response and impact resistance comparable to those of the wrought alloy. Furthermore, under high impact momentum, both the wrought and the AMed alloys fail due to the adiabatic shear band. A transmission electron microscopy analysis of the deformed alloys suggests the dissolution of the γ’ precipitates in the shear band as well as in the adjacent regions to the shear band. Increase in the rate of dissolution of the precipitates due to strain-assisted diffusion coupled with an increase in the adiabatic temperature during deformation, are likely causes of the dissolution of the precipitates in the shear band regions. © 2018 Elsevier B.V.

Keywords
3D printers; Deformation; Dissolution; Dynamic response; Heat resistance; High resolution transmission electron microscopy; Optical microscopy; Shear bands; Solidification; Strain rate; Superalloys; Transmission electron microscopy, Adiabatic shear band; Eutectic solidification; Heat treatment conditions; High strain rate deformation; Inhomogeneous distribution; Interdendritic regions; Microstructural analysis; Strain-assisted diffusion, Heat treatment
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13038 (URN)10.1016/j.msea.2018.09.079 (DOI)000450377700014 ()2-s2.0-85054099188 (Scopus ID)
Note

Funders: Natural Sciences and Engineering Research Council of Canada 

Available from: 2018-10-26 Created: 2018-10-26 Last updated: 2019-05-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9065-0741

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