Materialwissenschaft und Werkstofftechnik最新文献

This study investigates the effects of mechanical strain on the surface roughness of copper conductors, focusing on the electrolyte-refined copper (Cu-ETP, CW004A) used in H07V-U 1.5 mm² single-core cables. For the first time, the surface roughness evolution is characterized using the power spectral density (PSD) function, enabling a detailed roughness analysis across different spatial length scales. Conductors were subjected to mechanical stress, with measurements taken at multiple stages of service life. The study confirms the results from other studies that surface roughness increases significantly in the early stages of loading, with a plateau observed in 50 % - 75 % of cycles to failure. Micro crack formation and material extrusion are identified as key mechanisms driving roughness growth, especially at small length scales, with a shift towards larger length scales as strain intensifies. The increasing Hurst exponent suggests a transformation from a random to a more persistent and correlated surface. The results underscore the potential of power spectral density analysis in understanding surface behavior in copper conductors.

Sandwich composites are used in automobiles, aerospace, shipbuilding and structural applications in civil engineering. In the present investigation, glass fibre reinforced aluminium foam (AA6061-T6) sandwich laminates are fabricated in four different layers of 1 mm-thickened aluminium foam (0, 1, 2 and 3) that have been combined with epoxy resin in the hand layup method. The four different combination samples were indexed as S1 – S4. The tensile, flexural, impact strength and hardness test were performed to study the mechanical properties of the developed sandwich composites, and the morphological study of tensile fractured specimens was carried out using scanning electron microscopy (SEM). The results indicated that the morphologies of the sandwich composites enhanced their mechanical characteristics by increasing the bonding between the epoxy and aluminium foam. The two-layer aluminium foam sandwich composite (S2) has better mechanical properties than the other three aluminium foam sandwich composites, including tensile (102.3 MPa), flexural (7.7 kN), impact strength (11.9 kJ/m²) and hardness (242 HV 10), which indicates its enhanced structural performance. The mechanical strength of the aluminium foam sandwich composite is further supported by the findings of scanning electron microscopy scans. This work advances engineering in the real world by offering a useful guideline for improving aluminium foam layers in sandwich composites.

This study characterizes the wear behavior of an aluminum/copper laminated composite with a highly uniform distribution using a wear test under various sliding and loading conditions. The composite is processed through up to twelve accumulative roll bonding passes to achieve a uniform distribution. The microstructure, mechanical, and wear properties are characterized using optical microscopy, scanning electron microscopy, tensile testing, hardness testing, and wear tests. The ultimate tensile strength of 321 MPa, coupled with an elongation at a break of 9.7 %, is achieved after twelve passes. For lower loads and sliding distances, the amount of weight loss decreases due to the increase in hardness (154 % for aluminum and 174 % for copper compared to the raw sheets) in the strain-hardened layers. However, with an increase in the applied load (from 5 N to 10 N) and sliding distance (from 500 m to 1500 m), weight loss increases, which is due to the higher contact stress between the pin and wear surfaces, resulting in greater depth of deformation and surface temperature, which accelerates the recrystallization process in the plastically deformed region. Additionally, based on the wear test results, various wear mechanisms, including adhesion, abrasion, and delamination, are observed.

In the form of bar, rod and plate, aluminum alloy Al6061 has been widely used as components in many applications. In the current investigation, the effect of silica nanoparticles on the physical and mechanical behavior of Al6061-based nanocomposite has been investigated. Al6061-based nanocomposites were prepared using stir casting machine. Characterization properties for the investigation taken were hardness, void content, tensile strength, flexural strength, fracture toughness, and thermal conductivity. The inclusion of 3 wt.-% silica nanoparticle increased the void content, hardness, tensile strength, flexural strength, and fracture toughness by 44 %, 5.1 %, 52 %, 8 %, and 18.6 % respectively. However, the composite made of Al6061 had a 4 % reduction in thermal conductivity. The best percentage of nanosilica for mechanical and thermal conductivity properties of Al6061 based composite was 9 wt.-%. Hence, nanosilica can be suggested as promising reinforcement for composite material applications requiring high strength and low thermal conductivity.

This study systematically investigated boronizing treatment and its effect on the corrosion behavior and microstructure of the iron - 20 % chromium - 5 % boron - 3 % aluminum alloy in molten zinc. Diiron boride, α-iron, and dichromium boride exist in the as-cast iron - 20 % chromium - 5 % boron - 3 % aluminum alloy. The boronizing treatment was conducted using the pack cementation method, the α-iron phase on the alloy surface was transformed into the more zinc corrosion-resistant diiron boride phase. Boron diffusion and enrichment turned the original diiron boride and dichromium boride into iron boride and chromium boride. Performance of the alloy before and after boronizing treatment was compared through a 128 h molten zinc corrosion test. Although chromium and aluminium in alloy enhance its corrosion resistance in molten zinc, the α-iron phase is still prone to preferential corrosion. The less corrosion-resistant α-iron disappears and a complete boride layer forming on the surface of the alloy in boriding process significantly improves the overall corrosion resistance of the alloy in molten zinc. Since the newly formed iron-boron compounds are interleaved with the original iron-boron compounds, the adhesion property of surface boride layer is guaranteed.

The effect of aluminum contents on the microstructure and mechanical properties of as-extruded magnesium-aluminum-calcium alloys was systematically investigated. The as-solid alloys with three aluminum contents contain block-shape calcium aluminide phases and aluminum-manganese intermetallic phases. Differently, the amounts of block-shape calcium aluminide phases and aluminum-manganese intermetallic phases increased with aluminum contents. During hot extrusion process, the block-shape calcium aluminide phases and aluminum-manganese intermetallic phases are fragmented into small pieces and aligned along the extrusion direction. Bimodal microstructures were obtained after extrusion, consisting of fine dynamically recrystallized grains and coarse deformed grains. The area fractions of dynamically recrystallized grains increased from 53 % to 65 % with aluminum contents increasing from 3.12 % to 5.21 %, due to the particle stimulated nucleation mechanism caused by block-shape aluminum-containing phases. The as-extruded magnesium-aluminum-calcium alloys show a strong basal fiber texture, which diminished as aluminum contents increase. The strength of as-extruded magnesium-aluminum-calcium alloys diminished as aluminum contents increased. The as-extruded magnesium-3.12 aluminum-2.65 calcium (wt.-%) alloy demonstrates a yield strength of 366 MPa and an ultimate tensile strength of 391 MPa. The exceptional high strengths are due to the ultrafine dynamically recrystallized grains stabilized by fragmented second phases, strong basal texture and high dislocation density.

The present investigation compares two fabrication techniques, gravity die casting and centrifugal casting, for fabricating homogeneous and functionally graded material composites based on their mechanical and wear characteristics. Therefore, composite samples were fabricated by incorporating different weights of silica nanoparticles in vinyl ester containing a fixed amount of walnut shell filler. The choice of walnut shell filler and vinyl ester as the reinforcing and matrix materials, respectively, was deliberate, as these materials possess unique characteristics that make them suitable for composite fabrication. Tests were conducted on fabricated samples of both gravity die casting and functionally graded material. It was found that gravity die casting composites exhibit better tensile strength and impact energy, while functionally graded material composites showed better hardness and wear resistance. In addition, void formation is much lower in functionally graded material composite, demonstrating the effectiveness of the centrifugal technique in producing composites with fewer defects.