| 1. |
- Ahmadkhaniha, Donya, et al.
(författare)
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Studying the Microstructural Effect of Selective Laser Melting and Electropolishing on the Performance of Maraging Steel
- 2021
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Ingår i: Journal of materials engineering and performance (Print). - : Springer. - 1059-9495 .- 1544-1024. ; 30:9, s. 6588-6605
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Tidskriftsartikel (refereegranskat)abstract
- Selective laser melting is one of the additive manufacturing technologies that have been known for building various and complicated shapes. Despite numerous advantages of additive manufacturing technologies, they strongly influence the microstructure and typically show a relatively high surface roughness. In this study, maraging steel was produced by selective laser melting (SLM), and its microstructure, hardness and corrosion behavior before and after heat treatment were studied and compared to traditionally manufactured ones (wrought, forged samples). In addition, the effect of electropolishing on the surface roughness was evaluated. The microstructural study was carried out by scanning electron microscopy equipped with electron backscattered diffraction in three different sections: parallel to the top surface (xy), transverse cross section (xz) and longitudinal cross section (yz). The same characterization was applied to heat-treated samples, austenitized and quenched as well as the aged ones. The results showed that selective laser melting produced a fine grain martensitic structure (in the as-printed condition) with a surface roughness (R-a) of about 10 mu m. There was no sign of preferred texture or anisotropy in the microstructure of as-print SLM materials. The SLM microstructure was similar in all 3 sections (xy, xz and yz). Despite finer microstructure, nano-hardness and corrosion behavior of SLM and conventional wrought maraging steel in heat-treated conditions were similar. Aging resulted in the maximum nano-hardness and the minimum corrosion potential values. Precipitation has the main role in both hardness and corrosion behavior. Electropolishing was optimized and reduced the surface roughness (R-a) by 65%.
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| 2. |
- al-Karawi, Hassan, 1993
(författare)
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Corrosion Effect on the Efficiency of High-Frequency Mechanical Impact Treatment in Enhancing Fatigue Strength of Welded Steel Structures
- 2022
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Ingår i: Journal of Materials Engineering and Performance. - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 31:11, s. 9151-9158
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue and corrosion are two material degradation phenomena that occur in welded steel structures. High-frequency mechanical impact (HFMI) treatment is a post-weld treatment method that aims to increase the fatigue strength of welded details. This paper investigates the effect of steel corrosion on the efficiency of this method in enhancing fatigue resistance. More than 150 fatigue test results on corroded and HFMI-treated welded details are collected from several research articles and analyzed for both transverse welded attachment and butt-welded details. The efficiency of HFMI treatment decreases in corroded details as the corrosion level increases. However, HFMI treatment is found to have a high potential in prolonging the fatigue life, even in circumstances of an extremely corrosive environment.
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| 3. |
- Al-Saadi, Munir, et al.
(författare)
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Hot Deformation Behaviour and Processing Map of Cast Alloy 825
- 2021
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Ingår i: Journal of materials engineering and performance (Print). - : Springer Nature. - 1059-9495 .- 1544-1024.
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Tidskriftsartikel (refereegranskat)abstract
- Alloy 825 is a nickel-based alloy that is commonly used in applications where both high strength and corrosion resistance are required, such as tanks in the chemical, food and petrochemical industries and oil and gas pipelines. Components made from Alloy 825 are often manufactured using hot deformation. However, there is no systematic study to optimise the processing conditions reported in literature. In this study, a processing map for as-cast Alloy 825 is established to maximise the power dissipation efficiency of hot deformation in the temperature range of 950 to 1250 °C at an interval of 50 °C and strain rate range of 0.01s−1 to 10.0s−1 to a true strain of 0.7 using a Gleeble-3500 thermomechanical simulator. The processing conditions are also correlated to the Vickers hardness of the final material, which is also characterised using optical microscopy and scanning electron microscopy, including electron backscattered diffraction. The true stress-true strain curves exhibit peak stresses followed by softening due to occurrence of dynamic recrystallization. The activation energy for plastic flow in the temperature range tested is approximately 450 kJ mol−1, and the value of the stress exponent in the (hyperbolic sine-based) constitutive equation, n=5.0, suggests that the rate-limiting mechanism of deformation is dislocation climb. Increasing deformation temperature led to a lower Vickers hardness in the deformed material, due to increased dynamic recrystallization. Raising the strain rate led to an increase in Vickers hardness in the deformed material due to increased work hardening. The maximum power dissipation efficiency is over 35%, obtained for deformation in the temperature range 1100-1250 °C and a strain rate of 0.01s−1-0.1s−1. These are the optimum conditions for hot working.
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| 4. |
- Ashrafi, Hamid, et al.
(författare)
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Damage Micromechanisms in Friction Stir-Welded DP600 Steel during Uniaxial Tensile Deformation
- 2022
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Ingår i: Journal of materials engineering and performance (Print). - : Springer. - 1059-9495 .- 1544-1024. ; 31, s. 10044-10053
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Tidskriftsartikel (refereegranskat)abstract
- In this study, damage initiation micromechanisms in friction stir-welded DP600 steel sheets during tensile deformation were studied by scanning electron microscopy (SEM) and electron backscatter diffraction. For this purpose, DP600 steel was welded using friction stir welding with two combinations of rotational and transverse speed, to prepare joints with low and high heats. Microhardness measurements on the cross section of the weldments revealed the formation of a softened zone in the HAZ as a result of the tempering of the martensite, which led to the localization of strain and failure during the tensile testing. SEM observations on the cross section of tensile tested specimens showed that ferrite–martensite interface decohesion and martensite fracture are the main void nucleation mechanisms in the DP600 steel. For the sample welded with low heat input, ferrite–martensite interface decohesion started at higher strains compared to the DP600 steel. A new void initiation mechanism including plastic deformation of tempered martensite, necking, separation of martensite fragments and formation of a void between the separated segments was also suggested for this sample. For the sample welded with high heat input, formation of void at the ferrite–cementite interface was the main void nucleation mechanism and ferrite–martensite interface decohesion was an inactive mechanism.
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| 5. |
- Babu, Karthik, et al.
(författare)
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Fire Behavior of 3D-Printed Polymeric Composites
- 2021
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Ingår i: Journal of materials engineering and performance (Print). - : Springer. - 1059-9495 .- 1544-1024. ; 30:7, s. 4745-4755
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Tidskriftsartikel (refereegranskat)abstract
- 3D printing or additive manufacturing (AM) is considered as a flexible manufacturing method with the potential for substantial innovations in fabricating geometrically complicated structured polymers, metals, and ceramics parts. Among them, polymeric composites show versatility for applications in various fields, such as constructions, microelectronics and biomedical. However, the poor resistance of these materials against fire must be considered due to their direct relation to human life conservation and safety. In this article, the recent advances in the fire behavior of 3D-printed polymeric composites are reviewed. The article describes the recently developed methods for improving the flame retardancy of 3D-printed polymeric composites. Consequently, the improvements in the fire behavior of 3D-printed polymeric materials through the change in formulation of the composites are discussed. The article is novel in the sense that it is one of the first studies to provide an overview regarding the flammability characteristics of 3D-printed polymeric materials, which will further incite research interests to render AM-based materials fire-resistant.
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| 6. |
- Banijamali, Seyed Masih, et al.
(författare)
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Experimental and Simulation Study on Wear Behavior of ZK60 Alloy with 3 wt.% Yttrium Addition
- 2022
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Ingår i: Journal of materials engineering and performance (Print). - : Springer Nature. - 1059-9495 .- 1544-1024. ; 31:6, s. 4721-4734
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of 3 wt.% of Y addition on the wear behavior of ZK60 extruded alloy was investigated using both experiment and simulation. First, a pin-on-disc tribometer was used to test dry sliding wear against an AISI 52100 steel counterface in a load range of 5-60 N. Microstructural study revealed that adding Y to ZK60 alloy resulted in substantial grain refinement and formation of new precipitates. The wear rate and friction coefficient were reduced with Y addition, attributed to the formation of new precipitates and increased hardness. Increasing the normal load resulted in a transition from mild to severe wear. In the mild wear regime, abrasion was the dominant wear mechanism, while in the severe wear regime, oxidative wear and delamination (a sign of spallation of oxidized patches) coexisted with abrasion were dominant mechanisms. Finally, finite element method was employed to model the wear behavior of studied alloys using ABAQUS software. A 3D model was developed to predict the wear depth evaluated from contact pressure, which was then used as an input into Archard's wear equation. In terms of wear rate, simulation results were in good agreement with experimental values, particularly in the mild wear regime.
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| 7. |
- Bejjani, Roland, et al.
(författare)
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Advanced Manufacturing of Titanium Alloy Ti-6Al-4V by Combining Cryogenic Machining and Ultrasonic-Assisted Turning
- 2024
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Ingår i: Journal of Materials Engineering and Performance. - 1059-9495 .- 1544-1024. ; 33:13, s. 6507-6527
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Tidskriftsartikel (refereegranskat)abstract
- Cryogenic and ultrasonic-assisted turning have both beneficial effects on the machinability of difficult-to-machine materials, such as titanium alloy Ti-6Al-4V. This research investigates the effect of combining both cryogenic and ultrasonic-assisted machining, to assess the effects on cutting temperature, forces and tool wear. The research utilizes FEM and CFD models to provide a better understanding of the interaction between the mechanisms at work during the machining process—namely the ultrasonic motion of the tool and the cryogenic impingement of the tool. The experimentation is then conducted to prove the effectiveness of combining both methods in reducing the cutting forces and reducing tool wear. The combined process is compared to conventional turning, cryogenic turning and ultrasonic-assisted turning. The CFD and FEM results showed a decrease in tool and chip temperature by 7.26% and 13.86%, respectively, when compared to UAT. The cutting forces in the combined turning show a reduction of 22% when compared to conventional turning. Tool wear is analyzed for the 4 cases. Tool wear caused by adhesion is shown to decrease in the new combined cutting method. This research has scientific as well as potential industrial applications in the machining of difficult-to-machine materials.
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| 8. |
- Hatami, Sepher, et al.
(författare)
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Fatigue Strength of 316 L Stainless Steel Manufactured by Selective Laser Melting
- 2020
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Ingår i: Journal of materials engineering and performance (Print). - : Springer. - 1059-9495 .- 1544-1024. ; 29, s. 3183-3194
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the fatigue strength of 316 L stainless steel manufactured by selective laser melting (SLM) is evaluated. The effect of powder layer thickness and postmachining is investigated. Specimens were produced with 30 and 50 µm layer thickness and tested under high cycle fatigue in as-printed and postmachined conditions. Examination of the specimens reveals that in the as-printed condition, fatigue strength suffers from high roughness and surface tensile residual stresses as well as defects such as pores and lack of fusion voids. After machining, the fatigue strength was improved due to lower surface roughness, presence of compressive residual stresses, and removal of surface porosity. The results show that increasing the layer thickness (within the range tested) has a minor negative impact on fatigue strength; however, it has a major positive impact on the productivity of the SLM process. In addition, it is clear that the impact of postmachining on fatigue is far greater than that of the layer thickness. © 2020, The Author(s).
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| 9. |
- Holmberg, Jonas, 1976-, et al.
(författare)
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Influence of Local Electropolishing Conditions on Ferritic–Pearlitic Steel on X-Ray Diffraction Residual Stress Profiling
- 2024
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Ingår i: Journal of materials engineering and performance (Print). - : Springer. - 1059-9495 .- 1544-1024. ; 33, s. 3682-
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Tidskriftsartikel (refereegranskat)abstract
- Layer removal with electropolishing is a well-established method when measuring residual stress profiles with lab-XRD. This is done to measure the depth impact from processes such as shot peening, heat treatment, or machining. Electropolishing is used to minimize the influence on the inherent residual stresses of the material during layer removal, performed successively in incremental steps to specific depths followed by measurement. Great control of the material removal is critical for the measured stresses at each depth. Therefore, the selection of size of the measurement spot and electropolishing parameters is essential. The main objective in this work is to investigate how different electrolytes and electropolishing equipment affect the resulting surface roughness, geometry, microstructure, and consequently the measured residual stress. A second objective has been to establish a methodology of assessing the acquired electropolished depth. The aim has been to get a better understanding of the influence of the layer removal method on the accuracy of the acquired depth. Evaluation has been done by electropolishing one ground and one shot peened sample of a low-alloy carbon steel, grade 1.1730, with different methods. The results showed a difference in stresses depending on the electrolyte used where the perchloric acid had better ability to retain the stresses compared to the saturated salt. Electropolishing with saturated salt is fast and results in evenly distributed material removal but has high surface roughness, which is due to a difference in electropolishing of the two phases, ferrite, and pearlite. Perchloric acid electropolishing is slower but generates a smooth surface as both ferrite and pearlite have the same material removal rates but may cause an increased material removal for the center of the electropolished area. In this work, it is suggested to use perchloric acid electropolishing for the final layer removal step. © 2023, The Author(s).
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| 10. |
- Holmberg, Jonas, 1976-, et al.
(författare)
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Progressive Induction Hardening : Measurement and Alteration of Residual Stresses
- 2024
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Ingår i: Journal of materials engineering and performance (Print). - 1059-9495 .- 1544-1024.
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Tidskriftsartikel (refereegranskat)abstract
- Progressive induction hardening is an in-line steel heat treatment method commonly used to surface harden powertrain components. It produces a martensitic case layer with a sharp transition zone to the base material. This rapid process will induce large residual stresses, where a compressive state in the case layer will shift to a tensile state in the transition zone. For fatigue performance, it is important to quantify the magnitude and distribution of these stresses, and moreover how they depend on material and processing parameters. In this work, x-ray diffraction in combination with a layer removal method is used for efficient and robust quantification of the subsurface stress state, which combines electropolishing with either turning or milling. Characterization is done on C45E steel samples that were progressively induction hardened using either a fast or slow (27.5 or 5 mm/s, respectively) scanning speed. The results show that although the hardening procedures will meet arbitrary requirements on surface hardness, case depth and microstructure, the subsurface tensile stress peak magnitude is doubled when using a fast scanning speed. However, the near-surface compressive residual stresses are comparable. In addition, the subsurface tensile residual stress peak is compared with the on-surface tensile stresses in the fade-out zone.
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