Materialwissenschaft und Werkstofftechnik最新文献

Temperature control of mould surfaces is of high relevance for part quality in moulding processes. Due to highly dynamic heating behaviour, heating elements applied by thermal spraying can be an alternative to existing tempering methods. To ensure the feasibility of these heating coatings on industry-relevant moulds, the coating system needs to be applied onto more demanding non-flat geometries. For this purpose, the spray angle of the plasma spraying process is varied during the application of the titanium oxide/chromium oxide heating coating and the insulating aluminium oxide coating. Subsequently, the results are related to application-oriented cavity shapes. Spray angle deviations from the optimal perpendicular angle are leading to decreasing dielectric strength of the coating system and an increase of the electrical resistivity. Additionally, the application efficiency reduces with the spray angle variation. Knowledge of the spray angle's influence on coating properties can help to coat more demanding shapes, including free formed surfaces or corners.

Since the solidification structure of metals cast by conventional mold casting often has porosity defect, the combination of low voltage pulsed magnetic field and thermally controlled solidification was used to solve this defect. The combination method is called magnetic-thermal coordinated control solidification. Pulsed magnetic field stirring can refine equiaxed grains, and the thermally controlled solidification method can eliminate the concentrated shrinkage cavity and reduce the dispersed shrinkage porosity. Thus, a superalloy K4169 with fine equiaxed grains, low content of dispersed shrinkage porosity and without concentrated shrinkage cavity defect is fabricated by magnetic-thermal coordinated control solidification.

Aerospace and automotive industries, among others, utilize reinforced aluminium metal matrix composite materials extensively. Aluminium alloy 5052 matrix was reinforced with tungsten carbide and titanium dioxide particulate reinforcements by varying their weight fractions, to fabricate the hybrid composites. The melt-stir casting route was used to process the materials, and their characteristics were determined by measuring Vickers microhardness, tensile strength and peak elongation. The cost-effectiveness and productivity of the melt-stir casting route led to its selection. Investigations were carried out to assess how reinforcement particles were mixed into the aluminium alloy matrix using scanning electron microscopy and energy-dispersive x-ray analysis. The microstructure of aluminium alloy 5052 showed a distinct homogenous structural integrity. Adding tungsten carbide and titanium dioxide particles to aluminium alloy 5052 led to a 6.57 % rise in the Vickers microhardness value. The tensile strength of the hybrid composites made of aluminium, tungsten carbide, and titanium dioxide increased by as much as 8.7 %. The findings demonstrated that all of the hybrid composites failed due to particle fracture and ductile fracture in the case of the as-cast aluminium alloy 5052.

Hailstorms today have the potential to damage almost every object in their path. Efforts are been made to prevent hailstorms, which can be quite severe. However, a completely successful result has not been achieved. Automobiles are the ones most damaged by hailstorms. In order to protect automobiles from this damage, various protective fabrics have been studied on and patents have been obtained. Spacer fabrics are one of the materials that have the potential to be used as protectors. In this study, an experimental device that can test the performance of spacer fabrics against hail and simulate hail damage has been designed and manufactured. At the same time, suggestions for the preparation of artificial hail grains that can be used in different studies are presented. With 25 mm and 30 mm diameter artificial hail grains, experiments were carried out on spacer fabrics of different thicknesses with the same weave structure. The same diameters of artificial hail grains were also tested without covering and the amount of damage in all experiments was measured. As a result, it was compared which fabric provided how much protection against artificial hailstones of different diameters.

The present paper describes the fabrication and wear behaviour of CaO and MgO added stabilized zirconia (ZrO₂) ceramics produced by powder metallurgy method were examined and modelling with artificial neural networks was studied using the experimental data obtained. CaO/MgO added stabilized zirconia ceramics were fabricated by using a combined method of ball milling, cold pressing - cold isostatic pressing and sintering. CaO and MgO in different amounts (0–8 %mole) were mixed with zirconia. These mixtures were prepared by mechanical alloying method. The green compacts were sintered at 1600 °C. The wear experimental results obtained were converted into data suitable for modelling with artificial neural networks. Wear Load, wear time, CaO and MgO data were used as artificial neural networks input variables. The amount of wear according to the pressing method was taken as the output variables of artificial neural networks. An artificial neural networks was established for the prediction of wear properties of zirconia pressed using the adaptive neuro fuzzy inference systems (ANFIS) learning technique. As a result, a high R² value of 0.9187 for cold pressing samples and 0,9449 for cold isostatic pressing samples was achieved based on the approach of comparing the success of the model with the test data set and the result produced.

In the current study, dental nanocomposite reinforced with silanized silicon dioxide nanoparticles was developed. The silicon dioxide nanoparticles were varied from 0 to 30 weight-%. Polymer resin of bisphenol A-glycidyl methacrylate/ triethylene glycol dimethacrylate (BisGMA/TEGDMA) was used along with camphorquinone and ethyl 4-(dimethylamino) benzoate as polymerization initiator and accelerator respectively. The role of silicon dioxide nanoparticles in mechanical and viscoelastic properties of dental composites was evaluated. Physical properties like void content and water sorption were increased by 10 % and 25 % respectively. However, mechanical and viscoelastic properties were improved with the addition of silicon dioxide nanoparticles. Data were analyzed statistically with one-way analysis of variance (ANOVA) and post hoc Tukey′s HSD test (α<0.05). The incorporation of 10 weight-% of silicon dioxide nanoparticles increased the micro-hardness by 126.1 %, compressive strength by 7.6 % and flexural strength by 28.8 %. The storage modulus was increased by 37 % and loss modulus was decreased by 1 % with the introduction of 10 weight-% of silicon dioxide nanoparticles.

The aim of the research is to investigate the weldability of thick sections of carbon steel using submerged arc welding with varying process parameters. The experimental design for joining thick carbon steel involves manipulating input weld process parameters such as current (A), voltage (V), weld speed (mm/h), and weld electrode diameter (mm). The quality of the weld material is assessed based on transformations in microstructure, weld hardness measured by Brinell hardness number, and tensile strength (MPa). It is crucial to note that the grain structure and metallurgical behavior of other hard materials may differ significantly. The presence of carbon in the ferrite phase has led to the formation of bainite, martensite, and composites of martensite and austenite within the weld zone, as confirmed by high-resolution microscopy. The weldment‘s hardness has increased from 242.5 HV 30 in the base metal to 316.4 HV 30 in the weldment due to metallurgical alterations in the microstructure. Weld energy input emerges as the primary factor influencing weld quality. With increasing weld current and voltage, there is a corresponding increase in the joined metal, resulting in improved characteristics in the weld structure, particularly at maximal energy input and welding speed. In the context of boiler applications, understanding the weldability of thick carbon steel sections is paramount for ensuring structural integrity and longevity under high-temperature and high-pressure conditions. The optimized welding parameters identified in this study can contribute to enhancing the reliability and performance of boilers, thereby promoting safety and efficiency in industrial settings.

Synthesis of two-dimensional (2D) titanium carbide (Ti₃C₂T_x), with the name of MXene, by etching Ti₃AlC₂ (MAX) for different times 20 (v/v) % hydrofluoric acid (HF) at 40 °C was carried out. The influences of time, temperature and source of MAX on the synthesis of MXene were researched. The MXenes produced were characterized by fourier-transform ınfrared (FT-IR) spectroscopy technique, energy dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), x-ray diffraction (XRD) and thermogravimetry (TG) instruments. Above 390 °C, MXene layers were considerably oxidizing and forming anatase and rutile phases of TiO₂ under air atmosphere. The resistance of MAX and MXene was 3.6 Ω and 116 Ω, respectively. However, the resistance of the residual part of MXene heated to 620 °C considerably increased to 17850 Ω. This behavior is another important piece of evidence showing that the MXene crystal structure has changed significantly and transformed into a new chemical structure containing anatase and rutil titanium oxide (TiO₂). The dielectric loss (ϵ’’) and alternating conductivity (δ_ac) of the MAX and MXenes were determined from their impedance measurements. The ϵ’’ and δ_ac values of MXene were compared with those of MAX. Direct curent conductivities of MAX and MXene produced for 24 h were found to be 0.016 S/cm and 0.0023 S/cm, respectively.

The research aims to forecast the mechanical performance of a hybrid woven fabric natural composite subjected to compression, utilizing the three-dimensional finite element method. A detailed finite element model of a plain woven fabric unit cell is created and analyzed for different materials like flax, basalt, and jute, and combinations of these materials (inter-yarn hybrid basalt-flax, jute-flax and basalt-jute fabrics). It is observed that fabric‘s response to compression is mainly influenced by the transverse longitudinal shear behaviour and the stiffness of the yarn cross-section. Compression of single-layer woven fabric involves yarn bending and compaction, resulting in varying fiber volume fractions in different areas due to compaction. The basalt-jute hybrid plain woven fabric outperformed other plant-based fiber fabrics with a polypropylene matrix in terms of mechanical performance under compression. Increase in yarn spacing and fabric thickness resulted in higher strain energy and displacement, attributed to changes in fiber volume fraction and crimp angle. Whereas, increasing yarn width led to a stiffer fabric due to increased contact area at the crossover region and higher bending rigidity, resulting in decreased strain energy and displacement. Importantly, this developed model can effectively simulate textile fabrics with diverse weaving patterns, material properties, and loading conditions.

Utilization of inorganic waste, if included in composite material, can be beneficial in reducing the accumulation of waste, which could help in resolving problems of disposal. beside from that, incorporating waste into composite materials also reduces the overall cost of the composites as a whole. The study examines the impact of dolomite content on the mechanical properties of the composites. Increasing the amount of dolomite in the composite significantly weakens its flexural strength, falling from 42.4 MPa at 0 % dolomite to 28.7 MPa at 15 % dolomite. Composite tensile strength also decreases by up to 25.8 % with rising dolomite dust concentration. Additionally, dolomite increases interlaminar shear strength (ILSS), with EDH15 composites showing the highest improvement. Dolomite dust in epoxy-based composites increases the hardness value from 85 HRL to 95 HRL with an increase in dolomite dust content. The erosion test perform on air jet tester shows lowest wear rate was achieved under the following conditions: 10 % dolomite dust weight, 30° impingement angle, 10 m s⁻¹ impact velocity, and 150 μm erodent size. Furthermore, scanning electron microscopy was used to examine the damaged, eroded surfaces for assumed wear mechanisms.