Friction welding of selective laser melted Ti6Al4V parts Prashanth, K.G.; Damodaram, R.; Maity, T. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
09/2017, Volume:
704
Journal Article
Peer reviewed
Ti6Al4V alloy samples fabricated by selective laser melting (SLM) were subjected to solid-state welding friction welding (FW). The welded alloy exhibits a α´-martensitic microstructure in the form of ...platelets with dimensions in the submicron regime. The base alloy has a relatively coarser microstructure consisting of both α´ and β-phases, as compared to the as-prepared SLM microstructure (single-phase α´martensite). Hardness measurements revealed an increase of hardness in the weld zone due to the refined α´platelets. A marginal drop in hardness along the base alloy is observed that may be attributed to the imposed thermal cycle during the FW process. Tensile tests reveal an improved ductility for the FW samples at the expense of a marginal drop in strength, compared to the as-prepared SLM samples. The present work illustrates the ability of solid-state welding processes for successfully joining SLM parts and in improving, the ductility of the SLM parts and offers the opportunity to work with the additive manufacturing processes without size limits.
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IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A novel multi-physics computational framework for L-DED process is proposed.•Particle-scale thermofluidic model is integrated with Cellular Automata approach.•Realistic Inconel-625 particle stream ...predicted by DEM modelling is utilized.•Results reveal highly oscillatory and chaotic melt flow due to impinging particles.•Predicted melt pool, temperature, and grain structure compare well with experiments.
High speed imaging of molten pool free-surface hydrodynamics in laser-assisted directed energy deposition process clearly revealed a highly oscillatory and dynamic melt flow due to impinging powder particles. Surprisingly, most of the reported computational work exclude the injection of powder particles and rather adopt a homogeneous mass and energy addition approach, and therefore provides less accurate predictions. In this work, we develop a coupled multi-physics particle-scale approach utilizing the discrete element method for particle trajectory prediction, the computational fluid dynamics for free-surface thermo-fluidic modelling and the cellular automata method for grain growth evolution. In the model, the governing physical phenomena, such as laser-powder interaction, in-flight particle heating, phase change (melting, vaporization and solidification), free-surface evolution, molten pool hydrodynamics and impinging particles-melt interaction have been considered. Experiments for the deposition of Inconel-625 on an Inconel-625 substrate are carried out, and the model predictions are validated with the experimental measurements. For the first time, the predicted thermo-fluidic simulation results reveal highly oscillatory, chaotic and random melt flow attributed to the impinging powder particles. During the deposition, it is found that the role of the Marangoni convection is less significant as compared to the momentum imparted by the impinging powder particles in the melt pool. Using the simulated thermal undercooling data, cellular automata-based grain growth simulation predicts elongated columnar dendrites in the melt pool that grows epitaxially from the melt pool interface and stretches towards the centre. Using the Kurz-Fisher model, the effect of local thermodynamic solidification conditions on the size of dendritic microstructure is also described. The predicted melt pool geometry, temperature field and grain structure compare well with the experimental measurements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A novel Al-based composite reinforced with Ti-based metallic glass (MG) nanoparticles was fabricated by powder metallurgy through mechanical alloying combined with hot extrusion. During the ...ball-milling process, MG microparticles were refined into nanosized particles through severe plastic deformation. Hot extrusion of the milled powders resulted in a dense and uniform dispersion of the metallic glass nanoparticles in the Al-7075 matrix. This unique homogeneous structure led to a significant enhancement of strength without adversely affecting the plasticity, thus developing super-high specific yield strength. The yield strength increased from 297 MPa for Al-7075 matrix to 530, 610, 880, and 1014 MPa for the composites milled for 10, 15, 30, and 50 h, respectively. A critical analysis of the different factors contributing to the strength of the composites was carried out. Grain refinement, Orowan strengthening, and dislocation–dislocation interactions were demonstrated to be the most important contributors to the enhanced strength of the nanocomposite.
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IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This study’s novel 13Ni400 maraging steel parts are additively manufactured through a selective laser melting process. The Taguchi approach is adopted to evaluate the combined influence of process ...variables (energy density), viz., laser power, layer thickness, hatch spacing, and scan speed, on responses like relative density, microhardness, surface roughness, and tensile strength. The powder and material characterization studies are conducted in terms of an optical microscope, scanning electron microscope (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and fractography analysis to explore the pre- and post-fabrication scenarios of the build parts. The consequences of energy density and process variables are studied through meticulous parametric studies. Finally, the optimum level of built parameters is identified and validated by a confirmative test predicting an average error of ~1.80%. This work is proficient in producing defect-free parts with maximum densification and improved mechanical properties for newly developed 13Ni-400 maraging steel by the selective laser melting (SLM) technique.
The effect of annealing on the tribological and corrosion properties of Al–12Si samples produced by selective laser melting (SLM) is evaluated via sliding and fretting wear tests and weight loss ...experiments and compared to the corresponding material processed by conventional casting. Sliding wear shows that the as-prepared SLM material has the least wear rate compared to the cast and heat-treated SLM samples with abrasive wear as the major wear mechanism along with oxidation. Similar trend has also been observed for the fretting wear experiments, where the as-prepared SLM sample displays the minimum wear loss. On the other hand, the acidic corrosion behavior of the as-prepared SLM material as well as of the cast samples is similar and the corrosion rate is accelerated by increasing the heat treatment temperature. This behavior is due to the microstructural changes induced by the heat treatment, where the continuous network of Si characterizing the as-prepared SLM sample transforms to isolated Si particles in the heat-treated SLM specimens. This shows that both the wear and corrosion behaviors are strongly associated with the change in microstructure of the SLM samples due to the heat-treatment process, where the size of the hard Si particles increases, and their density decreases with increasing annealing temperature.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Friction welding of electron beam melted Ti-6Al-4V Qin, P.T.; Damodaram, R.; Maity, T. ...
Materials science & engineering. A, Structural materials : properties, microstructure and processing,
07/2019, Volume:
761
Journal Article
Peer reviewed
Ti-6Al-4V samples produced by electron beam melting (EBM) are welded using solid-state friction welding (FW) process. The microstructure of the weld sample shows the presence of fine equiaxed α ...grains with irregular β phase. Microstructural investigations reveal a pronounced change in the shape and size of the α phase in the weld metal as-compared to the base material along with the disappearance of columnar prior β grains. Such variations in the microstructure significantly change the mechanical properties of the FW material. The hardness in the weld zone increases and a decrease of hardness is observed along the heat affected zone (HAZ) with respect to the base metal as expected. Similarly, the room temperature tensile tests show an improvement of ductility in the welded EBM samples. However, the yield and the ultimate strength show a marginal drop in the welded samples compared to the as-prepared EBM specimens. The present work demonstrates that solid-state FW process not only permits successful joining of additively manufactured materials, but also helps in improving their ductility.
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IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study aimed to investigate the microstructure and tribological properties of the equiatomic AlCoCrFeNi high-entropy alloys (HEAs) fabricated using selective laser melting (SLM) and spark plasma ...sintering (SPS) processes. Sliding wear behavior in a ball-on-disk configuration with a ball either above or below the disk of the SLM and SPS samples was investigated. A detailed study of the effects of wear debris on the sliding wear behavior was undertaken to clarify the effect of wear debris entrapment in a wear scar. The wear volumes in the as-built SLM samples were slightly higher than in the SPS counterparts in both configurations. Wear volume and coefficient of friction values in the ball-above configuration were significantly lower than in the ball-below configuration. The present results indicated that the wear debris significantly influenced the mechanical contact properties of the HEA, providing new insight into the performance of the new materials in various conditions that could be considered to widen classical approaches by including the fate of the detached particles in the wear process. The impacts of wear debris on the design and application of these novel alloys should be considered.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Recently, there has been an upsurge in the use of naturally available fuels for solution combustion synthesis (SCS) of nanoparticles. Although many reports suggest that these biofuels pose less harm ...to the environment, their strategic advantages and reliability for making NPs has not been discussed. In the present work, we try to address this issue using plant extracts as biofuels for the SCS of zinc oxide nanoparticles as a model system. In the present work, combustion synthesis of ZnO NPs using lactose and aqueous leaf extracts of Abutilon indicum, Melia azedarach, Indigofera tinctoria as biofuels has been carried out. A comparative analysis of the obtained powders has been conducted to understand the strategic advantages of using plant extracts over a chemical as combustion fuel for the synthesis of zinc oxide nanoparticles. The X-ray diffractograms of the samples revealed the presence of Wurtzite hexagonal structure with varying crystallite sizes. Morphological studies indicated that samples prepared using biofuels had smaller diameter than those prepared using lactose as fuel. Surface characteristics of the samples were measured by X-ray photoelectron spectroscopy. Qualitative phytochemical screening of aqueous leaf extracts revealed the presence of many phytochemicals in them, which might be responsible for combustion. Gas chromatography mass spectrum was carried out to detect the phytochemicals present in the aqueous extracts of the leaves. Further, anticancer evaluation carried out against DU-145 and Calu-6 cancer cells indicated higher anticancer activity of zinc oxide nanoparticles prepared using biofuels. The results of blood haemolysis revealed the biocompatibility of zinc oxide nanoparticles at lower concentrations. In conclusion, we propose that multiple other studies would be required in order to vindicate the potential advantages of using naturally available fuels in SCS.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Herein we summarize the production of silver/copper oxide nanocomposites (Ag/CuO NCs) by a facile solution combustion method with the aid of abio-fuel as reductant. Powder XRD results revealed the ...formation of Ag/CuO NCs with average crystallite size ranging from 20 to 25 nm. These NCs were tested for their antimycobacterial activity against four mycobacterium species namely
Mycobacterium tuberculosis H37Rv ATCC 27294, Mycobacterium abscessus ATCC 19977, Mycobacterium fortuitum ATCC 6841, Mycobacterium chelonae ATCC
and anticarcinogenic activity on breast cancer cell line MDA-MB-231. Scavenging activity was evaluated by the 2, 2-diphenyl-1-picrylhydrazyl hydrate (DPPH) method. Results indicated that the Ag/CuO NCs had higher anticancer and slightly better scavenging activities than the undoped CuO nanoparticles.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In situ fabrication of TiB whiskers (TiBw) reinforced Ti-matrix composites (TMCs) was carried out with the addition of TiB2 particles in Ti6Al7Nb matrix using low energy ball milling and subsequent ...consolidation via Spark Plasma Sintering (SPS). The ball mixing of 0.5 %, 1.5 %, and 3 % TiB2 resulted in its distribution ratio (RD) of 1.05, 3.2, and 6.5, respectively. The in situ TiBw formations as a reaction between the Ti6Al7Nb matrix and TiB2 particles resulted during sintering. This TiBw inclusion in different regions caused the retardation of grains from growing and resulted in grain refinement. The presence of a stiff TiBw phase in combination with grain refinement was ascribed to the increased hardness and higher strength in the fabricated composites. Maximum hardness (~ 496 Hv) and strength (~ 2233 MPa) was achieved in the 3 % TiB2 containing composites among all. The biological response showed better cell adhesion and proliferation without any toxic effect on all fabricated samples when compared to the wrought Ti6Al7Nb. The enhanced cell proliferation on the TiBw composites than the pure alloy demonstrates them as promising materials for biomedical applications.
•The fine in situ TiB reinforcement as a result of TiB2 addition was done.•Fine TiB distribution provided microstructure refinement and strengthening of the composites.•Appreciable mechanical and biological response was recorded.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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