Materialwissenschaft und Werkstofftechnik最新文献

In recent years, the investigation of natural fibres as viable replacements for engineered fibres has gained significant prominence. Natural fibres come with remarkable environmental attributes, including biodegradability and renewability. This work aims to analyze the physical, mechanical, and wear behavior of grewia optiva-walnut filler-based epoxy composites. The walnut shell content varies from 0 wt.–%–12 wt.–%, whereas grewia optiva fibre is kept constant (i. e., 10 wt.–%) for all fabricated compositions. The results revealed that the 9 wt.–% of walnut content-based composites exhibited a higher value of tensile strength (123.9 MPa) and flexural strength (52.03 MPa), whereas higher hardness, which is 38.33 HV 5, was achieved for the 12 wt.–% of walnut content. Moreover, the influence of selected control variables, i. e., walnut content, sliding velocity, normal load, and sliding distance, on the specific wear rate (SWR) of the composites was ranked using the Taguchi analysis. Further, scanning electron microscope (SEM) analysis has also been performed for fractured surfaces.

The benefits of green technology have industrial use of composites reinforced with biofibers garner attention. They are replacing conventional plastics due to their capability to solve environmental issues. Despite this shift in material development, the synthesis of biodegradable biocomposites still poses a challenge due to their wide range of properties. This work focuses on developing biofilaments for fused filament fabrication from recycled high-density polyethylene and rice husk waste in varying proportions to study the effect of their different ratios on the biofilaments. High-density polyethylene though very popular, has not been widely explored in fused filament fabrication due to warping challenges and high thermal shrinkage of printed parts upon solidification. The addition of organic fillers has been proposed as a way to reduce these challenges. Rice husk waste has been used as a filler in polyethylene for conventional processes such as extrusion, injection molding, and pressing but not widely in additive manufacturing. In this study, a particle size of less than 75 μm and the use of a compatibilizer improved its miscibility in the polymer's matrix. The highest composition of the biofilament achieved was 35 % rice husks, 35 % recycled high-density polyethylene, and 30 % compatibilizer, an improvement of the rice husk filler from previous studies. Printability was attained up to a biofilament composition of 40 % recycled high-density polyethylene, 30 % rice husks, and 30 % compatibilizer. The maximum tensile strength, tensile modulus, and maximum tensile strain of this biofilament were 8.53 MPa (standard deviation of 1.32 MPa), 6.6 % (standard deviation of 0.03 %), and 128.56 MPa (standard deviation of 13 MPa), respectively. Though the addition of rice husk filler reduced the tensile strength, there was an improvement in the crystallinity of the biofilament which improved the shrinkage and warpage of the printed part. This work thus demonstrated an improvement in the rice husk content as a filler in biofilaments made from recycled high-density polyethylene with enhanced biodegradability.

The integration of EN AW 7075 aluminium in Body in White structures is a promising way to achieve weight savings, which in turn can make a significant contribution to reducing CO₂-emissions. However, due to hot cracking susceptibility, conventional welding technologies offer limited possibilities to join the material. Therefore, laser beam welding in vacuum is introduced as a comparatively new joining technique. The investigations show, that it is possible to weld the EN AW 7075 alloy in an overlap joint configuration without pores or microcracks appearing in the weld seam. The weld seam has a very fine-grained structure, which presumably has a favourable effect on hot cracking mechanism. The prevention of cracking is likely due to the lower temperature gradient between the capillary wall and the fusion line caused by the low evaporation temperature due to the reduced pressure. The reduced temperature results in lower residual stresses, which presumably has a positive effect on the tendency to hot cracking. In addition, the fine-grained structures can absorb strain better than coarse grain structures, that usually occur in conventional laser beam welding.

This study aimed to synthesize, characterize, and evaluate the adhesion strength of titania nanotubes (titania nanotubes) and iodine-doped titania nanotubes (I-titania nanotubes) architectures on the additively manufactured Ti-6Al-4 V (Ti64) implant surface. The titania nanotubes and I-titania nanotubes were synthesized through two stages of electrochemical anodization, whereby titania nanotubes are anodically fabricated through a conventional approach and then modified by replacing the ethylene glycol electrolyte with potassium iodide solution. The characterization results revealed the formation of α-Ti, β-Ti, and titanium iodide (TiI₂) phases on the titania nanotubes and I-titania nanotubes surfaces. The morphology of titania nanotubes exhibits a consistent diameter, evenly distributed, well-ordered array, and densely packed nanotubular structures. Formation of a water-soluble fluoride-rich [TiF₆]² complexes in the inner titania nanotubes surface and incessant nanotube′s sidewall etching resulted in poor interfacial titania nanotubes adhesion to the titanium-substrate surface. Iodine doping on the titania nanotubes is believed to reduce the [TiF₆]² complexes accumulation and the titania nanotubes sidewall etching. This facilitates the adhesion and interfacial mechanical anchorage between the titania nanotubes and the surface of the Ti64 implant. The hardness and adhesion strength of the titania nanotubes increased by more than 50 %, due to the formation of a hard titanium iodide film at the titania nanotubes/I-titania nanotubes surfaces and interfaces.

Slurry erosion is the prominent failure mechanism in the components exposed to particle entrained slurries. The slurry erosion wear behaviour of powder metallurgically processed Al2124 composite is investigated under slurry conditions with parameters like the impingement angle, impact velocity, slurry concentration, and stand-off distance. Aluminium oxide of 690 μm size is chosen as the erodent and the slurry jet erosion tester is used. The L₁₆ orthogonal array is used for the experimental design and the most influencing parameters were identified using the analysis of variance (ANOVA) results. Among the parameters studied, slurry concentration and impact velocity are observed to be the most influencing parameters on the erosion rate and surface roughness. Further, the experimental results are compared with those predicted by the regression and artificial neural network (ANN) models. The wear profile analysis of eroded samples shows U and W shape profiles for oblique and normal impact angle conditions respectively. Al2124 composite exhibits ductile erosion behaviour. The material removal mechanisms are analysed by scanning electron microscopy.

The abstract presents a study on the impact of cooling on the substrate during the wire arc additive manufacturing process on microstructure, mechanical properties, and corrosion behaviour of deposited specimens of manganese-rich low-carbon steel. Through a combination of experimental investigations and quantitative analyses, the study reveals the correlations between varying cooling rates and resulting material properties, such as finer grain structure. The cooling rate has been measured through the thermocouple temperature and observed time till room temperature. The average hardness increased from 172 HVN to 183 HVN and ultimate tensile strength increased from 526 MPa to 585.17 MPa which is 11.2 % higher with a significant increase in elongation from 22.3 % to 32.4 % due to the finer grain structure and reduced heat-affected zone. The result also shows how the corrosion behaviour changes with the solidification rate and also illuminates the effect on surface roughness. This work contributes to advancing the understanding of process-structure-property relationships in additive manufacturing and offers insights for cooling strategies to achieve desired material characteristics in this specific context.

Vanadium carbide (VC) nano-particles were introduced into sintered Nd−Fe−B magnets for the purpose of grain refinement and coercivity enhancement. The effect of vanadium carbide (VC) addition on the microstructure and magnetic properties evolution of sintered Nd−Fe−B magnets was studied. Based on the characterization results, the additive vanadium carbide (VC) nano-particles mainly reacted with rare earth (RE)-rich phase to form ferrovanadium (FeV) phase, which rooted in the grain boundary. The ferrovanadium (FeV) phase inserted influence on the dissolution-precipitation process and acted as pinning sites and heterogeneous nucleation sites, which was favorable for the grain refinement. As a result, the coercivity of sintered magnets enhanced significantly from 13.62 kOe to 16.15 kOe without obvious decline of remanence when the vanadium carbide (VC) nano-particles additive amount increased from 0 wt.–% to 0.1 wt.–%. The above findings shed light on the microstructure manipulation to obtain high performance sintered magnets.