•Effect of laser remelting on mechanical properties under cyclic loading was studied.•Effect of laser remelting on wear volume and friction coefficient was studied.•Effect of laser remelting and heat ...treatment on Charpy impact energy was studied.•Anisotropy in hardness, residual stress, Charpy impact energy and wear was studied.•Reciprocating sliding tests with ball above and below configuration were conducted.
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The reliability and quality of additively manufactured parts are questionable. The present study aimed to improve the surface quality and mechanical and tribological properties of a Ti6Al4V alloy manufactured using selective laser melting (SLM). The effects of the laser remelting on its surface topology, mechanical properties, and sliding wear in a ball-on-plate configuration with a ball either above or below the plate were investigated systematically. The influence of the laser remelting approach on the anisotropy of the mechanical and tribological properties was compared with that of the heat treatment approach. The surface quality and high cycle fatigue strength improved with an increase in the number of melting steps. The compressive and impact strengths also increased with an increase in the number of melting steps. The wear resistance in both configurations was higher in the remelted samples than in the samples after SLM. The results confirmed that laser remelting, as an affordable approach, could significantly improve the reliability of parts fabricated by the SLM process.
The powder particle properties in additive manufacturing processes such as selective laser melting (SLM) influence the material properties. The microstructure, hardness, and chemical composition of ...gas-atomized AlCoCrFeNi powder particles were investigated, which showed a biphasic structure, consisting of FCC and BCC with a significant deviation in hardness. SLMed samples, consisting of BCC phase, indicated poor printability, inhomogeneous microstructure, and cracks. Microstructural inhomogeneity of SLM AlCoCrFeNi parts must reflect the inhomogeneity inherited from the atomized powder.
Graphical Abstract
The evolution of microstructure and texture during selective laser melting (SLM) of silver alloy—sterling silver 925 (AM Ag925) has been investigated and analyzed
vis-à-vis
cast sterling silver (AC ...Ag925). The microstructure of AM Ag925 was characterized by a single-phase silver-rich face-centered cubic solid solution with dendritic morphology, along with some locally distributed micro-segregated copper–germanium (Cu–Ge)-rich regions. Each adjacent dendritic feature consists of Ag–Cu-rich and Ag–Ge-rich regions and appears as alternate dark and bright regions. On the other hand, the as-cast AC Ag925 microstructure comprises Ag and Cu phases. Specific heat treatment was employed, which led to an equiaxed microstructure in AM Ag925 with Cu distributing along grain boundaries while the microstructure of AC Ag925 had Cu precipitates inside the matrix. Bulk texture studies revealed that the solidified textures were very weak for AM Ag925, and a random texture is observed. On the other hand, for the AC Ag925 specimens, a typical fiber texture is observed. Both AC Ag925 and AM Ag925 showed significant deviation from
100
solidification texture and influences the mechanical properties.
In-situ multicomponent alloying in additive layer manufacturing shows inhomogeneous elemental distribution. This study aimed to minimize this inhomogeneity in equiatomic CoCrFeMnNi high entropy alloy ...(HEA) produced by selective laser melting (SLM) from a mixture of elemental powder. A detailed study was undertaken regarding the effects of remelting scan strategy on microstructural and mechanical properties, melt pool geometry, and elemental distribution of CoCrFeMnNi HEA manufactured using the SLM process. The SLM sample with remelting scan strategy showed a homogeneous elemental distribution. The remelted SLM sample showed a homogeneous hardness distribution. The X-ray diffraction of the as-built and remelted SLM showed a single-phase FCC structure, typical for a HEA. Prediction and observation of melt pool depth exhibited a lower depth in the remelted SLM samples. The microstructure of the melt pools of both as-built and remelted SLM showed a fine grain morphology, typical of rapid solidification. The boundary of melt pools in the as-built SLM and the inter-space of melt pools in the remelted SLM consisted of both coarse and equiaxed/columnar dendritic grains. The present results confirmed the possibility of fabricating a homogenized CoCrFeMnNi HEA from mixed elemental powders using SLM with remelting scan strategy.
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•In-situ alloying of equiatomic CoCrFeMnNi HEA using SLM process was investigated.•Laser remelting effect on elemental distribution and grain morphology was examined.•Melt pool size of SLM samples was estimated and compared with experimental value.•Laser re-melting – microstructure – mechanical property relationships were studied.
Development in the microstructure and mechanical properties of as-built TiC-Fe based cermets fabricated through selective laser melting (SLM) adapting pulse shape technique has been studied and is ...compared after post-treatment process like hot isostatic pressing (HIP). Pulse shaping temporarily distributes the energy uniformly within the single layer of pulses and the laser material exposure can be controlled with controlled energy delivery. For the fabrication of TiC-based cermets, laser beam optimization proves to be an effective fabrication method to produce crack-free cermets. Some porosity may be observed in as-built samples due to a lack of fusion and poor feedstock powder rheology. The maximum hardness and fracture toughness values achieved for the as-fabricated samples are found to be 1020 ± 50 HV and 16.5 ± 1.5 MPa m
1/2
. Post-processing treatments such as HIP performed at high temperature and high pressures were adapted, where the hardness decreases (due to microstructural coarsening) and fracture toughness show a marginal increase (due to pore closure).
Selective laser melting (SLM) based processing of Mo-based samples is challenging due to solidification cracking. We here demonstrate that the addition of 2 wt% MoS2 to the Mo feedstock markedly ...improves crack mitigation of SLM-processed Mo/MoS2/Mo2S3 composite micro-lattice structures (SLM-Mo/Mo(x)S(x+1)). Crack inhibition is suggested to be a result of Mo2S3 formation, decreased lattice strain (0.044%), and a decrease in accumulated residual stresses. The increased values of polarization resistance from 42.3 and 19.2 kΩ cm2 to 437 and 78.2 kΩ cm2, respectively verified the hindering effect of the composition on stress corrosion cracking (SCC) and surface oxidation cracking. However, an increased corrosion current density, from 1.22 to 10.2 μA/cm2, and cathodic Tafel constant, from 175 to 260.5 mV, confirmed the decreased polarization resistance and occurrence of different types of corrosion such as SCC and pitting. The strategy to add 2 wt% MoS2 to the Mo feedstock enables the fabrication of high-temperature micro-lattice structure components with improved corrosion resistance properties applicable in e.g., electronic, power semiconductor heat sinks, offshore-, aerospace-, defense-, or particularly novel sodium-ion energy storage applications.
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•The addition of MoS2 bilaterally affects the mitigation of structural defects and improvement of corrosion resistance.•The processability of Mo-based micro-lattices of a brittle BCC crystallographic structure is enhanced.•The lattice strain is alleviated, and crystallographic texture is maintained constant.•Improved crystallographic characteristics hinder stress corrosion cracking (SCC) susceptivity.•Thermodynamically transformation of MoS2 to Mo2S3 inhibits the surface of micro-lattice from pitting and oxidation cracking.
Technology of Severe Plastic Deformation (SPD) has emerged as a widely known procedure for the fabrication of ultrafine grained metals and alloys. Equal Channel Angular Pressing (ECAP) are one of ...methods of SPD has been developed for many applications; military devices, aerospace and automotive components. This paper examines recent developments related to the use powder of Aluminum alloys processed by consolidation-ECAP, for grain refinement; Al-5Mg, were compared by another type of Aluminum, which has also been researched. Characterization by mechanical, physical and microstructured. In the current study powder of material wrapped in copper capsule to be compressed and heated at a temperature of 400°C in hot press under the pressure of 450-500 MPa. Afterward the powder in solid condition was cooled in the air. The sample results of Aluminum by ECAP process then followed heat treatment with type Annealed, for heating at a temperature of 346°C for 1,5 continuing 415°C during 2 hours followed by heating at a temperature of 205-230°C for 4 hours. This paper describes the effect of heat treatment on the characteristics of the powder material on Al-5Mg are based on changes in the mechanical properties and microstructures.
► Aluminium reinforced with
ex situ nano-SiC by powder metallurgy technology. ► Nature of the SiC nanoparticles and high-energy mixing methods are investigated. ► Effective nanoparticle dispersion ...estimated, using matrix crystallite size. ► 10
vol.% of SiC nanoparticles effectively mixed in aluminium for tensile response.
High-energy milling was studied for the
ex situ strengthening of aluminium with silicon carbide (SiC) nanopowders. Heptane was used as a milling agent for both planetary- and attritor ball milling. Considering the different milling techniques and the differences in the resulting powders, effective dispersion of the nano SiC was achieved. Composite samples compacted by hot pressing showed an increase in hardness (HV
20
=
220) and a decrease in Al crystallite size from 220 to 55
nm with the nano-SiC content increasing from 1 up to 20
vol.%. The ultimate tensile strength was measured for extruded samples which resulted in 205
MPa (17% elongation) for 1
vol.% of nano-SiC and a strength of 420
MPa (4% elongation) for 10
vol.% of nano-SiC reinforcement. The mechanical properties were compared with what was predicted by the Hall–Petch relationship.
Investigation of next-generation manufacturing methods for the processing of functional materials and offering products with improved performance/functionalities has always been a challenge in terms ...of energy efficiency, cost-effectiveness, and eco-friendliness. Additive manufacturing (AM) attributes to rapid prototyping techniques that provide new opportunities to test new concepts and design complex 3D structures from metals, ceramics, and composites. Moreover, as a well-known transition metal dichalcogenide, Molybdenum disulfide (MoS2) is a two-dimensional (2D) material with outstanding electrochemical, physical, and mechanical properties that make it a potential candidate for energy storage electrodes via intercalation of different H+, Li+, Na+, and K+ cations. In this review, we discuss the existing conventional MoS2-processing methodologies and compare them with the novel additive manufacturing processes (especially laser-based powder bed fusion). The authors are convinced that the processing of prominent MoS2-based functional structures by the novel additive manufacturing processes can provide complex structures for different electrochemical applications, particularly for energy conversion/storage systems.
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For the fabrication of brittle materials like cermets through Selective Laser Melting (SLM), the pulse shaping technique has proven to be an effective and optimal way to produce cermet with no ...cracks. The purpose of this work is to investigate the effect of laser peak in pulse shaping as a preheating and cooling approach for the melt pool of TiC − Fe based cermet using the pulse shaping technique. Several samples were fabricated with variations in laser power and exposure time refereed as pre-pulse and post-pulse before and after the laser peak power (LPP). Microstructural and phase analyses were performed on the fabricated SLM sample using SEM and XRD to study the effect of pulse shaping with variation in exposure time and therefore energy density. Mechanical properties like microhardness were calculated and hence the effect of hardness and energy density were studied. Results indicated that preheating and cooling through laser pulse during pulse shaping has a beneficial effect on the fabrication of the crack-free brittle cermet.
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