Textured Surface Layer Research Articles

Post-Machining Deformations of Thin-Walled Elements Made of EN AW-2024 T351 Aluminum Alloy as Regards the Mechanical Properties of the Applied, Rolled Semi-Finished Products

The paper presents an evaluation of post-machining deformations of thin-walled elements as regards the mechanical properties of the applied, rolled semi-finished products. Nowadays, wrought aluminum alloys, supplied primarily in the form of rolled plates, are widely applied in the production of thin-walled integral parts. Considering the high requirements for materials, especially in the aviation sector, it is important to be aware of their mechanical properties and for semi-finished products delivered after plastic working to take into account the so-called “technological history” concerning, inter alia, the direction of rolling. The study focused on determining the influence of the ratio of the tension direction to the rolling direction on the selected mechanical properties of the EN AW-2024 T351 aluminum alloy depending on the sample thickness and its relation to the deformation of thin-walled parts. Based on the obtained results, it was found that the sample thickness and the ratio of the tension direction to the rolling direction affected the mechanical properties of the selected aluminum alloy, which in turn translated into post-machining deformations. Summarizing, the textured surface layer had a significant impact on the mentioned deformation. Greater deformations were noted for samples made of a semi-finished product with a thickness of 5 mm in comparison to 12 mm. It was the result of the influence of the surface layer, which at lower thickness had a higher percentage of contents than in thicker samples.

Pre-Machining of Rolled Plates as an Element of Minimising the Post-Machining Deformations.

The paper presents the influence of the milling strategy, the relation between the cutting tool feed direction and the rolling direction, as well as the pre-machining consisting of the removal of the textured surface layer of rolled plates in the rolling process on the thin-walled elements deformations made of the EN AW-2024 T351 wrought aluminium alloy, after milling. The research used strategies such as: high-performance cutting (HPC), high-speed cutting (HSC) and conventional milling (CM), as well as their combinations. Another tested variable was the relation between the tool feed direction and the rolling direction. In addition, the tests were carried out in the following versions: leaving the textured surface layer created after plastic working and with its removal with technological parameters corresponding to HSC and CM. Based on the obtained results, it was found that the post-machining deformation of thin-walled elements can be minimised owing to the use of a selected milling strategy and its combination with pre-machining (or lack thereof). It was also observed that larger deformations were obtained for samples after milling in the direction perpendicular to the rolling direction.

Superhydrophobic corrosion resistant coatings for copper via IR nanosecond laser processing

A series of superhydrophobic coatings with contact angles, exceeding 170° and roll-off angles less than 1.6° on copper alloy was designed using nanosecond IR laser processing, followed by vapor deposition of fluorooxysilane molecules. The experimental data show that for all samples, the surface layer consisted of cupric and cuprous oxide and demonstrated multimodal roughness. The morphology and composition of a textured surface layer for four fabricated samples varied depending on the laser processing parameters. It was found that the variation of parameters of laser processing leads to variation in chemical and corrosion resistance of fabricated coatings. Coatings with higher ratio of cupric to cuprous oxide show notably better barrier properties of the oxide layer, better chemical resistance in contact with an aqueous medium, and lower corrosion rate in chloride-containing electrolytes. It was demonstrated that in agreement with the previously reported analysis of mechanisms of corrosion protection by the superhydrophobic coatings, the higher is the chemical resistance of the layer of hydrophobic molecules with respect to desorption from the surface the better is the protective potential. The variation of laser processing parameters allowed selecting a regime for obtaining the superhydrophobic coating, for which the prolonged contact with the saline solution is accompanied by a significant decrease in the corrosion rate and the prolonged preservation of the superhydrophobic state.

Influence of pre-machining on post-machining deformation of thin-walled elements made of aluminium alloy EN AW-2024

The paper presents analysis of influence of pre-machining, consisting of removing the textured surface layer of the semi-finished product formed after plastic working, on deformation of thin-walled elements made of EN AW-2024 alloy after milling. The textured layer was removed from surface opposite to the machined surface. During tests, the influence on thin-walled elements deformation of the following machining strategies was analysed: High Speed Cutting (HSC), High Performance Cutting (HPC), and hybrid strategies HPC + HSC, HPC + CM, and HPC + CM (CM – Conventional Machining). On the basis of received results it was determined that residual stresses stored in subsurface, rolled, and unmachined surface layer have significant influence on value and character of deformations of thin-walled elements. Removing the textured surface layer formed after rolling changes character and value of the deformations of thin-walled elements. The largest difference between samples with initially removed textured layer and samples without such machining was determined for HPC + CM milling strategy. For this strategy, deformations without pre-machining were much larger than in the case of samples with removed textured surface layer.

Structural and phase evolution in laser treatment of Al2O3–TiO2–Y2O3 powder mixtures

Abstract Directional laser irradiation of x mol.% Al 2 O 3 –y mol.% TiO 2 –z mol.% Y 2 O 3 powder mixtures forms concave tracks. They consist of three main layers: a lower sintered layer, a volume of crystallization products of eutectic alloy layer, and a thin textured surface layer. Phase formation proceeded within the framework of Al 2 O 3 –Y 2 O 3 and Y 2 O 3 –TiO 2 binary mixtures. Y 3 Al 5 O 12 , Y 2 Ti 2 O 7 , and Al 2 O 3 were observed after laser irradiation. The microstructure of the ceramic tracks depends on the ratio of the phases formed in rapid cooling of the eutectic melts.

Ultrafine-grained textured surface layer on Zr–1%Nb alloy produced by ultrasonic impact peening for enhanced corrosion resistance

An ultrafine-grained (UFG) surface layer was produced on Zr–1%Nb alloy using severe plastic deformation process induced by ultrasonic impact peening (UIP). XRD analysis and TEM observations allow establishing the links between the microstructure formed at different extents of the effective strain ē and superficial microhardness and corrosion resistance. In the topmost surface layer about 10μm thick, average grain size diminishes down to approx. 100nm after the UIP process for 4min (ē≈0.86). The mechanism of the grain subdivision is discussed on the basis of TEM observations of microstructure in surface layer at different strain extents with taking into account the dynamic recrystallization process facilitated by deformation induced heating. XRD analysis reveals high compressive residual stresses and strong basal texture. Two features of the surface layer formed after the UIP process, viz. UFG structure and strong basal texture, are considered to play the major roles in essential increase in microhardness (from 1 to 2.35GPa) and corrosion resistance of the Zr-1%Nb alloy in saline solution. Decreased surface roughness and large compressive residual stresses also promote higher corrosion resistance.

Enhanced Extraction Efficiency of InGaN/GaN Light-Emitting Diodes by Liquid Phase-Deposited Zinc-Oxide-Textured Window Layer

This paper proposes a method of improving the extraction efficiency of InGaN/GaN light-emitting diodes (LEDs) using textured zinc oxide (ZnO) prepared by liquid phase deposition (LPD). The treatment solution for liquid-phase-deposited ZnO (LPD-ZnO) consisted of hydrochloric acid (HCl) saturated with ZnO powder. The deposition temperature was maintained at 30 °C using a temperature-controlled water bath system. Atomic force microscope images of the LPD-ZnO indicate that the root-mean-square (RMS) roughness of the LPD-ZnO is dependent on the HCl concentration. As compared with conventional the InGaN/GaN LED, the extraction efficiency of the InGaN/GaN LED with the LPD-ZnO-textured layer increases in conjunction with RMS roughness. The maximum light output intensity enhancement of 48% for the InGaN/GaN LED with an RMS roughness of 16.26 nm occurred under a driving current of 20 mA. The calculated optical intensity of the InGaN/GaN LED with a bumplike LPD-ZnO-textured surface indicates that the optimum RMS roughness of the textured surface layer applied to InGaN/GaN LEDs is approximately 16 nm, which agrees with the experimental results. The InGaN/GaN LED with LPD-ZnO with an RMS roughness of 16.26 nm shows a wide light output divergence angle, which satisfies the requirement of the applications of a backlight source.

Nanostructured graded-index antireflection layer formation on GaN for enhancing light extraction from light-emitting diodes

We describe the fabrication and characterization of a randomly etched gallium nitride (GaN) surface for enhancing light extraction from light-emitting diodes. Our technique uses silica spheres as nano-targets in a sputter-etch process and produces a fine-grained surface with features around 35 nm. The textured surface layer acts as a graded refractive index layer with antireflection properties. Measurements show that photoluminescence intensity from such treated surfaces on a GaN LED wafer increases 2.2 times over that from pristine surfaces. These findings are also supported by computer modelling studies described here.

Improvement in Extraction Efficiency of GaN-Based Light-Emitting Diodes with Textured Surface Layer by Natural Lithography

In this study, p-side-up GaN-based light-emitting diodes (LEDs) with textured indium-tin oxide (ITO) or silicon dioxide (SiO2) surface layers were investigated by natural lithography using polystyrene spheres (PSs) as an etching mask. It was found that the ITO top layer provides better roughness than SiO2. Under the optimum surface treatment parameter, the roughnesses of textured ITO and SiO2 surface layers are 140 nm and 15 nm, respectively. The diameter of PSs in the textured ITO surface is still maintained at about 250–300 nm. Correspondingly, the size of PSs in the SiO2 surface is reduced to about 100 nm. The output powers of LEDs with textured ITO and SiO2 surfaces and conventional LEDs are 10.9, 9.5, and 8.5 mW at 20 mA, respectively. LEDs fabricated using the textured ITO surface produced an output power that exceeded that of planar-surface LEDs by about 28% at 20 mA dc current.

Surface crystallization and texture in cordierite glasses

Systematic work was carried out at 860°C ( T g∼800°C) on the crystal growth of a high-quartz solid solution phase (μ-cordierite), which crystallizes on solid impurities on the surface and in the volume of the same cordierite glass sample. Crystal growth velocities were determined for three different growth fronts: (I) crystals that nucleated on solid inclusions existing in the glass interior and grew radially; (II) isolated crystals that nucleated on the external sample surfaces and grew with the fast axes parallel to the surface, and (III) crystals that nucleated on the external surfaces and grew towards the specimen center, spontaneously forming a textured surface layer. The crystal growth velocities of the three fronts were equal. We conclude, therefore, that the mechanisms of molecular transport at the crystal–liquid interface (or interfacial rearrangement) for crystal growth on the surface and in the interior of cordierite glass are similar. X-ray diffraction investigations have shown that, in case (III), a fiber texture is spontaneously formed with preferential alignment of the c 0-axis of the grains normal to the growth front. The texture dispersion angle decreases towards the interior of the glass, in accordance with evolutionary microstructural models. The apparent induction times (≈2 h) for growth of internally nucleated crystals, case (I), and (≈3 h) for the isolated surface crystals, case (II), indicate that different nucleation sites have caused heterogeneous nucleation on the surface and in the glass interior. The long induction time for growth of the textured surface layer (≈11 h) is due to a succession of two different growth modes that form the texture in this glass.

Water and Chloride Movement Through a Layered Field Soil

AbstractTwenty porous ceramic samplers at each of four soil depths were arranged in a three‐dimensional pattern to study the movement of water and Cl‐ through a layered sandy loam (sandy, mesic typic Dystrochrepts) over a gravely coarse sand with a perched water table at ∼180 cm. All samplers were used as tensiometers during the initial phase of the experiment in which salt‐free water was ponded at the soil surface. After constant flow conditions were achieved, a pulse of 0.015 M CaCl2 solution was added to the infiltrating water and all samplers were then used to obtain soil water samples for Cl‐ analysis. Variations in soil water pressure were observed to be much smaller than the variations in Cl‐ concentration. Both water and Cl‐ data moved downward in a general one‐dimensional pattern in the finer textured surface layer and in the zone directly above the water table, whereas, the movement between these two depths was three‐dimensional, i.e., by fingering.

Investigation of polytetrafluorethylene surface texture

Results are given of an X-ray investigation of the formation of a textured surface layer on polytetrafluorethylene (PTFE) film and its dependence on external mechanical factors — unit load and sliding speed. It is established that the thickness of the surface texture of PTFE is determined by the relation between the processes of texture formation under the influence of frictional forces and its destruction by wear. These processes, in turn, are determined by the working parameters of the moving joint. Data on the kinetics of polymer surface texture formation in the presence of friction are extremely useful in relation to the design of efficient antifriction materials.