| 1. |
- Bjerke, Axel, et al.
(författare)
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Machinability improvement by in-operando Tool Protection Layers through designed steel alloying : The case of manganese steel
- 2024
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 330
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Tidskriftsartikel (refereegranskat)abstract
- Improvements in machinability by alloying of the workpiece often adversely impact the end user properties of a material. For example, the common use of non-metallic inclusions can lead to improved tool life during turning or milling, but often adversely affects weldability, corrosion, and wear resistance. A cutting tool material meets kilometers of workpiece material during a machining operation. Hence elements in small quantities in the workpiece may insignificantly affect the end user properties but may have large effects on tool wear. One such effect is the formation of refractory and wear resistant reaction products between the workpiece and tool. Such reaction products forming on tool surfaces may lead to improved machinability. This paper proposes the use of small amounts of alloying to induce such a Tool Protection Layer. Additionally, the paper develops a computational framework for designed alloying which balances formation of Tool Protection Layers, its in-process retention, and the functional properties of the alloy. The method has been validated for a case of manganese steel. The calculations were validated first by a wide range of diffusion experiments. Then by industrial turning of cast alloys, by comparing one reference and two newly designed alloys based on the alloying concept. The alloy with 0.003 mol fractions of Al resulted in more than 3 times increase in tool life, due to in-operando formation of Al2O3 Tool Protection Layer. The designed manganese steel maintained its functional properties with respect to abrasive wear resistance and retained its ability to work harden.
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| 2. |
- Chaudhary, Bhavesh, et al.
(författare)
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Friction stir powder additive manufacturing of Al 6061/FeCoNi and Al 6061/Ni metal matrix composites : Reinforcement distribution, microstructure, residual stresses, and mechanical properties
- 2023
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Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 319
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Tidskriftsartikel (refereegranskat)abstract
- Fusion based additive manufacturing (FBAM) of second, sixth, and seventh series Al alloys and their metal matrix composites (MMC) is difficult due to their higher thermal conductivity and solidification related problems namely porosity, cracks, thermal distortion, and formation of undesired phases. This paper presents friction stir powder additive manufacturing (FSPAM) process as a promising alternative to overcome these problems in producing multi-layer depositions of Al 6061 based MMCs namely Al 6061/6wt%FeCoNi and Al 6061/6wt%Ni. Their microstructure, distribution and elemental mapping of reinforcement particles, phase analysis, residual stresses of the MMCs and their correlation with microhardness, tensile strength, and fretting wear characteristics are investigated. Material accumulation on their advancing side was minimized by changing tool rotation direction in consecutive layers which produced smoother surfaces on both sides of their deposition. FSPAM made multi-layer depositions of Al 6061/FeCoNi and Al 6061/Ni MMCs have uniform distribution of reinforcement particles, good bonding between layers without cracks and defects, refined and equiaxed grains facilitated by dynamic recrystallization and pinning effect of reinforcement particles, compressive residual stresses of 39 and 48 MPa, no formation of deleterious intermetallic compounds due to absence of melting of matrix and reinforcement, and bowl-shaped substrate-deposition interface. Microhardness and ultimate tensile strength of the MMCs improved by 11.3% and 22.3%, and 30.5% and 31.5% respectively than Al 6061 alloy depositions, their wear resistance enhanced significantly, but % elongation reduced. This study proves FSPAM to be a potential alternative to FBAM processes for better quality multi-layer deposition of Al alloy-based MMCs.
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| 3. |
- Ganvir, Ashish, 1991-, et al.
(författare)
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Novel utilization of liquid feedstock in high velocity air fuel (HVAF) spraying to deposit solid lubricant reinforced wear resistant coatings
- 2021
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 295
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Tidskriftsartikel (refereegranskat)abstract
- The ability to axially inject liquid feedstock has encouraged the thermal spray research community to explore this concept to deposit coatings for various next generation functional applications. The current study explores the utilization of liquid feedstock in high velocity air fuel (HVAF) spraying to deposit solid lubricant reinforced wear resistant coatings for the first time. The study successfully demonstrates the use of a powder-suspension hybrid processing approach to incorporate a solid lubricant Boron Nitride (as suspension) in a wear resistant Cr3C2–NiCr (as powder) cermet matrix. Coatings were characterized using Scanning Electron Microscopy and Raman Spectroscopy to analyze their microstructure and phase constitution. The results show that the tribological performance of the hexagonal boron nitride (hBN)-incorporated composite coating was significantly better than the traditional powder-derived Cr3C2–NiCr coating. Such hBN-incorporated composite coatings are needed to improve the mechanical properties and enhance the overall tribological performance of metallic components used in various applications, especially at high temperature such as cylinder bore, pistons, deformation tools, etc. The limitations of liquid based lubricants at high temperature motivates the use of hBN reinforced composite coatings as it can form a protective solid lubrication tribo-film. The study concludes that the emerging HVAF technology can accommodate liquid feedstock and be successfully utilized to deposit hybrid powder-suspension composite coatings to create multi length scale microstructures which can be attractive for combining different tribological attributes in the same coatings system.
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| 4. |
- Gustafsson, David, et al.
(författare)
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Simulation of metal punching and trimming using minimal experimental characterization
- 2023
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Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 321
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a validated finite element modeling approach for simulating shear cutting, needing a minimal amount of experimental characterization. Only one uniaxial tensile test and one force–displacement relationship from a punching experiment are needed for calibration, with maintained prediction accuracy compared to more experimentally demanding approaches. A key ingredient is the observation that the Lode angle parameter is close to zero in the fracture region, postulating that the fracture strain only depends on stress triaxiality, with one free calibration parameter. The true stress–strain behavior is provided from inverse modeling of the tensile test, whereas the fracture model is calibrated using the punching test. The model is verified for different materials by comparing force–displacement curves for punching experiments not used in the calibration. The prediction error for the intrusion is below 4%. A validation is made for two setups. The local residual stresses are measured using Focused Ion-Beam Digital Image Correlation (FIB-DIC). The simulated values are within the experimental bounds. Cut edge morphology and plastic strains obtained by nano-indentation mappings are compared to simulation results, showing a decent agreement. For trimming, the cut edge morphology prediction performance decreases at 17% cutting clearance while it is maintained over the whole range for punching. The predicted hardness values have a mean absolute percentage error below 7.5%. Finally, the effect of element size and remeshing is discussed and quantified. The minimal experimental characterization and simulation effort needed, enables an efficient optimization of the cutting process in the industry.
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| 5. |
- Hentschel, Oliver, et al.
(författare)
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Influence of the in-situ heat treatment during manufacturing on the microstructure and properties of DED-LB/M manufactured maraging tool steel
- 2023
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Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 315
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Tidskriftsartikel (refereegranskat)abstract
- Due to high productivity, additive manufacturing (AM), and especially Directed Energy Deposition using laser and metallic powder (DED-LB/M) is attractive for manufacturing tools with integrated functionalities. This investigation was dedicated to DED-LB/M manufacturing of experimental maraging tool steel, characterization of the build microstructure with advanced electron microscopy and evaluation of hardness properties. High printability and low porosity of the final builds were observed, relative density was not lower than 99.5% for specimens manufactured with 600 W and 800 W, but microstructure and properties of the build had a gradient along the height. The characteristic hardness profile and microstructure, which were dependent on the manufacturing parameters, were observed. The top layers of manufactured maraging steel samples had a structure of martensite with precipitates presumably formed during solidification. The top layers were therefore softer to the depth of the austenitization isotherm. The higher hardness was measured in the inner regions which was a result of an in-situ heat treatment that the manufactured material was subjected to during layer-by-layer manufacturing. Thermal cycles during manufacturing resulted in precipitation hardening effect in the inner regions. Scanning and transmission electron microscopy confirmed the formation film-like and round particles in the as-build material, in top and inner regions. However, the quasicrystalline nano-sized R′-phase precipitates were observed only in the inner regions. The formation of the R′-phase precipitated during manufacturing as a result of the in-situ heat treatment was discussed as a reason for higher hardness (440 – 450 HV1) measured in the inner regions.
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| 6. |
- Liu, Jiangwei, et al.
(författare)
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Understanding the effect of scanning strategies on the microstructure and crystallographic texture of Ti-6Al-4V alloy manufactured by laser powder bed fusion
- 2022
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Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 299
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Tidskriftsartikel (refereegranskat)abstract
- In this work, experimental and numerical approaches are performed to explore the influence of scanning strategies on the microstructure, crystallographic texture as well as the mechanical behavior of Ti-6Al-4V alloy manufactured by Laser Powder Bed Fusion (LPBF). In-situ monitored data of the energy intensity show that different scanning strategies result in variations of energy intensity distribution. The characterization of the microstructure and crystallographic texture reveals that the sample with hexagon scan pattern displays the structure with columnar primary 13 phase, while the specimens with chessboard scan exhibit equiaxial-like morphology. EBSD and TEM results provide evidence of the appearance of residual 13 nanoparticles. A finite element model is developed to further explain the phase transformation during LPBF and the formation mechanism of residual 13 particles. The numerical results indicate that the appearance of the residual 13 phase is attributed to the preheating/reheating effect by the adjacent tracks and successive layers, and the final phase composition of the LPBF-built Ti-6Al-4V alloy combines the alpha ', alpha, and 13 phases. Findings in the present paper show that various scanning strategies lead to a clear diversification in the microstructure, crystallographic texture, and phase composition of LPBF-built samples, which opens a route towards the tailoring of mechanical properties and isotropic behaviors in additive manufacturing.
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| 7. |
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| 8. |
- Shi, Qimin, et al.
(författare)
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In-situ formation of particle reinforced Aluminium matrix composites by laser powder bed fusion of Fe2O3/AlSi12 powder mixture using laser melting/remelting strategy
- 2022
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 299
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Tidskriftsartikel (refereegranskat)abstract
- In-situ preparation of particle reinforced Al matrix composites (PRAMCs) by laser powder bed fusion (LPBF) is a promising strategy to strengthen Al-based alloys. The laser-driven thermite reaction can be a practical mechanism to in-situ synthesise PRAMCs. However, the introduction of elements oxygen by adding Fe2O3 makes the powder mixture highly sensitive to form porosity and Al2O3 film during LPBF, bringing challenges to prepare dense materials. This work develops an LPBF processing strategy combined with consecutive high-energy laser melting scanning and low-energy laser remelting scanning to prepare dense PRAMCs from Fe2O3/AlSi12 powder mixture. A high relative density (98.2 ± 0.55 %) was successfully obtained by optimising laser melting (Emelting) and remelting energy density (Eremelting) to Emelting = 35 J/mm2 and Eremelting = 5 J/mm2. Results reveal the necessity to increase Emelting to improve metal liquid’s spreading/wetting by breaking up Al2O3 films surrounding molten pools; however, the high-energy laser melting produced much porosity. Low-energy laser remelting could close the resulting internal pores, backfill open gaps and smoothen solidified surfaces. Although with two-times laser scanning, the microstructure still shows fine cellular Si networks with Al grains inside (grain size 370 nm) and in-situ nano-precipitates (Al2O3, Si and Al-Fe(-Si) intermetallics). Finally, the fine microstructure, nano-structured dispersion strengthening and high-level densification strengthen the prepared in-situ PRAMCs, reaching yield strength of 426 ± 4 MPa and tensile strength of 473 ± 6 MPa. Furthermore, the results can provide valuable information to process other powder mixtures with severe porosity/oxide-film formation potential considering the evidenced contribution of laser melting/remelting strategy to densify material and obtain good mechanical properties during LPBF.
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| 9. |
- Surmeneva, Maria A., et al.
(författare)
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In situ synthesis of a binary Ti–10at% Nb alloy by electron beam melting using a mixture of elemental niobium and titanium powders
- 2020
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 282
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Tidskriftsartikel (refereegranskat)abstract
- This study reports the results of the preliminary assessment to fabricate Ti-10at% Nb alloy by electron beam melting (EBM®) from a blend of elemental Nb and Ti powders. The microstructure of the EBM-manufactured Ti-10at% Nb alloys is sensitive to the following factors: different sintering properties of Nb and Ti powders, powder particle properties, material viscosities at varying melt pool temperatures, β-stabilizer element content and the EBM® process parameters. Three phases were observed in as-manufactured Ti-10at% Nb alloy: μm-size Nb phase, a Nb-rich β-solid solution surrounding Nb phase, lamellar structured α-phase and β-solid solution with different distribution and volume fraction. Thus, the combination of powder particle characteristics, very short time material spends in molten condition and sluggish kinetics of mixing and diffusional process in Ti-Nb alloy results in heterogeneous microstructures depending on the local Nb content in the powder blend and the EBM® process conditions.
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| 10. |
- Wang, Yafei, et al.
(författare)
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Grain structure and texture of the SLM single track
- 2020
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 281
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Tidskriftsartikel (refereegranskat)abstract
- The grain structure and texture of metal parts fabricated by selective laser melting (SLM) are of interest for their effect on the properties. The study of the SLM single track can reduce the variables to be concerned and, hence, facilitate the understanding of the development of grain and texture in the SLM process. In this work, the austenitic stainless 316L single tracks are fabricated at different scanning speeds, and they are characterized by electron backscattered diffraction (EBSD) from transverse, serial transverse, and longitudinal cross-sections. It is validated that curved grain is common in the SLM single track. The effects of the varied thermal gradient and the shape of the melt pool on competitive growth of grain are analyzed. All the three equivalent < 001 > orientations of the columnar grain are considered, which leads us to put forward a crystallographic feature of a favorable grain during the competitive growth in SLM. Such a crystallographic feature is validated by the texture of the SLM single track, especially the < 001 > // scanning direction (SD) texture.
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