Examination and Polishing of Surface Scratches on Handheld Devices

Pollution is a current environmental problem. Personal used mobile phones and devices with LCD displays are often thrown away only the optical matter. The renewal of these device surfaces is at the focus of common interest. Our examination was a well-defined micro-scratch test using a special microhardness and scratch tester equipment (MCT). This equipment provides four different means of analyzing the scratch: acoustic emission detection, tangential force measurement, scratch depth measurement, optical observation through a digital microscope. The scratches were made with normal force from 0.5 to 15 N, the same length (20 mm) with the same diamond indenter. The scratches were analyzed with contact and non-contact methods, laser surface topographical analysis, optical microscopic examination, and surface roughness testing. On the LCD display we created specified scratches with the MCT scratch tester and after these scratches had to be repaired by polishing. Three different polishing speeds and loads were used. The measured wear rates show that higher polishing loads result increased wear rates but this trend does not true for the polishing speed

Functionally Graded Al2O3–CTZ Ceramics Fabricated by Spark Plasma Sintering

We studied the fabrication of functionally graded Al2O3–CeO2-stabilized-ZrO2 (CTZ) ceramics by spark plasma sintering. The ceramic composite exhibits a gradual change in terms of composition and porosity in the axial direction. The composition gradient was created by layering starting powders with different Al2O3 to CTZ ratios, whereas the porosity gradient was established with a large temperature difference, which was induced by an asymmetric graphite tool configuration during sintering. SEM investigations confirmed the development of a porosity gradient from the top toward the bottom side of the Al2O3–CTZ ceramic and the relative pore volume distributed in a wide range from 0.02 to 100 μm for the samples sintered in asymmetric configuration (ASY), while for the reference samples (STD), the size of pores was limited in the nanometer scale. The microhardness test exhibited a gradual change along the axis of the ASY samples, reaching 10 GPa difference between the two opposite sides of the Al2O3–CTZ ceramics without any sign of delamination or cracks between the layers. The flexural strength of the samples for both series showed an increasing tendency with higher sintering temperatures. However, the ASY samples achieved higher strength due to their lower total porosity and the newly formed elongated CeAl11O18 particles

Gyártási paraméterek változtatásának hatása additívan gyártott titán alkatrészek mechanikai tulajdonságaira

Az additív gyártási technológiák napjaink feltörekvő alkatrész- előállító módszerei. A fém alapanyagok esetében adottak a technológia sajátosságai, azonban az anyagféleségek és a különböző eljárások miatt teljes mértékben nem ismert minden lehetőség. Vizsgálatainkban fémek közvetlen lézeres szinterezési (DMLS) technológiájával, Ti-6Al-4V alapanyagból gyártott próbatesteken, különböző gyártási paraméterek változtatásának, mechanikai tulajdonságokra való hatásait elemeztük. | Additive manufacturing technologies are today's most upcoming methods for manufacturing components. For metallic materials, the specific features of the technology are given, but not all the possibilities are fully known due to the different material properties and process parameters. In this article we analysed the effects on mechanical properties of different manufacturing process parameters on specimens made of Ti-6Al-4V using direct metal laser sintering (DMLS)

Nagy üvegképző hajlamú és nagy entrópiájú ötvözetek képződése és stabilitása

Két ötvözetcsalád, a tömbi formában előállított amorf (BMG) és a nagy entrópiájú (HEA) ötvözetek képződési mechanizmusát és stabilitását hasonlítjuk össze jelen közleményben. Az összehasonlítás fő elve az olvadékaik túlhűlési képessége a megszilárdulás folyamatában. A BMG-ötvözetek olvadékai a különböző típusú kémiai kötések miatt nagy túlhűlési hajlamot, s ebből eredően nagy üvegképző hajlamot is mutatnak. Ennek jellemző mechanizmusa a klaszterképződés, amellyel az atommozgékonyság s így a kristálycsíra-képződés is visszaszorul. A HEA-ötvözetek olvadékai nem mutatnak ilyen hajlamot. Nagy hőmérsékleten, közvetlenül az olvadáspont környékén, az olvadékfázissal azonos összetételű, rendezetlen szilárd oldat formájában kristályosodnak. A kétféle olvadéktípusban az eltérő atomi mobilitás tükröződik az olvadékok viszkozitásának eltérő hőmérséklet-függésében is. A HEA-ötvözeteknek a konfigurációs entrópia által dominált fázisstabilitásához elektronszerkezeti tényezők is hozzájárulnak: itt szerepet kap a d-elektronok részvétele az atomok közötti kötésekben

The Formation and Stability of Bulk Amorphous and High Entropy Alloys

Two kinds of phase stabilization mechanism are discussed and compared: the first is characteristic of the formation of bulk amorphous alloys, in which the high supercooling ability of multicomponent liquids is responsible for the glassy phase stabilization. Here the hindered nucleation of crystalline phases is the center phenomenon. The origin of this hindering is the slowing atomic mobility in the supercooling melt. In contrast the melt supercooling is negligible during the high entropy alloy formation. It is believed that stability of the crystalline single fcc phase is the consequence of the characteristic of high configurational entropy at high temperatures. However, the significance of this entropy-dominated stabilization is overestimated in several references. It has been concluded that transition metal contraction (arising from the d electron participation in the overall bonding state) does also contribute to the high temperature stability of fcc single phase in the high entropy alloys

Analysis of mechanical properties, microstructure, surface oxygen concentration and depth distribution of different heat-treated additive manufactured Ti–6Al–4V

Laser-based additive manufacturing (AM) of Ti–6Al–4V alloy has garnered increasing significance for its application in components within transportation systems. A notable advantage over conventional steel structures lies in the reduction of specific weight. Employing a layer-by-layer manufacturing approach enables the production of complex geometries, facilitating faster and cost-effective personalized part manufacturing with reduced material waste compared to conventional methods. Post-processing plays a crucial role between the AM process and the utilization of the part, influencing its strength properties and porosity. Heat treatment emerges as a viable option to alter the final part's properties. Despite its advantages, the AM of Ti–6Al–4V parts is still a rather expensive technology because of the costs of equipment, materials and postprocessing. Postprocessing (surface and heat treatment) cannot be avoided for cost reduction since the mechanical properties of the as-printed state are not favourable for the applications. However, we can decrease the costs of manufacturing by the reduction of auxiliaries for example the use of inert gas during annealing. The question that we expect an answer to from our investigation is whether there are any significant differences in mechanical properties between heat treatment in an inert atmosphere or without protection. Another question is that in the case of annealing without an inert atmosphere, the used micro-glass blasting is suitable for removing the oxide layer. The mechanical examinations covered conventional tensile tests and hardness measurements. The depth distribution of oxygen was investigated by Glow Discharge Optical Emission Spectrometry (GDOES) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (EDS)

The effect of laser cutting on the structure of amorphous glassy tapes

Although thin metal strips or amorphous ribbons offer a higher magnetic performance compared to the presently used thicker crystalline electrical steels in electric motors, they have been considered unsuitable to build the rotor and/or the stator of classical electric motors because of fabricating limitations. Nowadays the development of high efficiency electrical motors has an outstanding significance, so an attempt is made to apply the soft magnetic glassy tapes to build stator and rotor elements for this application. However Fe based amorphous ribbons are promissing base materials, but in order to use them, several additional requirements have to be satisfied, like cutting the soft magnetic elements into the appropriate shapes, avoiding the degradation (local crystallization) of the individual glassy elements. In this paper the heat affected zone of soft magnetic materials like FINEMET and METGLAS were examined after laser cutting. The investigations were focused on structural changes (XRD and DSC) and microhardness distribution of the heat affected zone which have a strong relation to mechanical properties for example embrittlement. These materials will be used in electric motors to increase its efficiency therefore it is important to us for later machinability and handling of laser cutted part

Formation tendency in transition metal based liquids and some related property changes in glassy state

The cluster formation tendency in supercooled liquids and the glass forming ability (GFA) are usually discussed independently in the literature [1, 2, 3]. In the present paper we try to connect these phenomena in order to reveal their common origin. In the first part of paper the thermodynamic background of cluster formation will be treated. Subsequently the manifestation in thermal and magnetic properties are discussed. The mechanism of amorphous-nanocrystalline transformation is also explained as cluster phenomena. Finally, some results in the field of Hinduced magnetic and structural changes will be reported