Materials Science Forum Vol. 812

Abstract: In order to achieve the desired polymer recycling standards, precise estimations are needed about the composition of the polymer waste streams. The technologies that are currently used for this purpose, such as the infrared spectroscopy and the pyrolysis are neither time nor energy efficient as the processes may take up to hours, moreover the results are usually concluded by only analyzing small fractions of the waste streams. Meanwhile, as the polymer consumption of the world is increasing, the recycling and recovery rates demanded by numerous laws and restrictions are getting higher as well. The aim of this paper is to introduce a new technology that utilizes centrifugal force to separate the different polymer components of a sample in a melted state, containing the most common polymers found in a regular waste stream. After the separation, using the calculation method that is described, the exact ratio of the different materials can be given as well. In order to show the possibilities hidden in this technology, two samples, containing PA/PS/PP and PET/PA/PS/PP respectively, were separated and analyzed. The promising results were verified using optical microscopy as well as Raman spectroscopy.

Abstract: Ferritic nitrocarburising is a surface alloying heat treatment, which can provide to components high surface hardness, thus improved wear resistance. In structural steels the porosity of white layer has a key role in wear resistance: the porosity is undesirable. For tool steels the absence of white layer is undesirable. Floe process is one way to decrease the porosity of white layer. During our experiments we applied a modified Floe process on two different steels. The acontol of this process is simpler than conventional process. We measured the micro-hardness as a function of depth from the surface, and we made microscopic examination to analyse the structure of nitrided layer.

Abstract: Large area ordered nanopatterning of RF sputter deposited amorphous AlO_x films has been carried out. The technique involves UV laser treatment of the samples through LB films of silica nanospheres. The hexagonal, close packed arrangement of the spheres was projected to the surface due to the laser treatment resulting in ordered structure of pits of ~200 nm diameter and 1,3 nm depth. The samples were caracterized by means of AFM and XTEM. The experimental results are in good agreement with the simulations.

Abstract: The goal of this research was to create a surface topography that would promote cell attachment onto Ultrafine-grained Grade 2 Titanium. Morphologies that assist the deposition of bone tissue and reduce colonisation by unwelcome bacteria onto dental implant surfaces are created most often by sand-blasting, chemical etching, or these two in combination. Discs of thickness 2 mm from the machined base material were prepared for this study. After machining, the samples were chemically etched. Three etchants were used: 30 % HCl and 85% H₃PO₄, and the two in combination. The etching temperatures were 20 °C, 40 °C, and 60 °C, the etching times were 5 minutes and 120 minutes. The surface morphologies of the discs were examined by confocal microscope and scanning electron microscope (SEM), and compared to the machined-only samples as reference values. Samples treated in the 30% HCl solution at 40 °C for 120 minutes and then in the 85 % H₃PO₄ solution at the same temperature and time altered macro and micromorphology together in ways which assist the attaching of bone.

Abstract: Car manufacturing is one of the main target fields of sheet metal forming: thus sheet metal forming is exposed to the same challenges as the automotive industry. The continuously increasing demand on lower consumption and lower CO₂ emission means the highest challenges on materials developments besides design and construction. As a general requirement, the weight reduction and light weight construction principles should be mentioned together with the increased safety prescriptions which require the application of high strength steels. However, the application of high strength steels often leads to formability problems. Forming Limit Diagrams (FLD) are the most appropriate tools to characterize the formability of sheet metals. Theoretical and experimental investigations of forming limit diagrams are in the forefront of todays’ research activities.

Abstract: The mechanical (reversible deformation, stress-strain diagrams, etc.) and thermal (transformation temperatures, hysteresis) characteristics of the thermoelastic martensitic transformations are in the focus of many manuscripts, however, other aspects of the transformations are given less attention. The relief formation accompanied with displacive transformations ensures the possibility of the direct observation of the mechanism and physical metallurgical characteristics of the martensite↔austenite transformations. The authors of the present manuscript applied the in situ optical microscopy method successfully using self-developed examination techniques and self-made heating stages to characterize the thermally induced displacive transformations in shape memory alloys (SMAs) and TWIP steels.

Abstract: Surface preparation for electron backscatter diffraction (EBSD) measurements requires a lot of time and experience. We chose a lath martensitic iron based alloy to demonstrate the efficiency of ion polishing techniques. The average image quality (IQ) values from the EBSD measurements were assigned to be the characteristic parameter for surface goodness. The ideal ion sputtering time and the angle of incidence were determined, and the corresponding inverse pole figure (IPF) and IQ maps were compared to the mechanical polishing treatment.

Abstract: The researcher work pushes the borders of the application of a high efficiency equipment, in the matter of metals. With this equipment, which already testified in the compound industry, a flasher query of some metal-related technological parameters could be easily available. Towards the searching, we shaped different compound copper-alloy samples, in different states, and accordingly we monitored the realignments. Following the shaping, the DMTA detected such microscopic transformations (as we expected), according to heating rate, whereby we could determine the specialities of the transformations. In order to monitor the effect of the work hardening, we applied two different shaping grade: 50% and 75%. The heat treatment already took place in the DMTA, using 3 K/min heating rate. The specimens were loaded by inflection in the 2-point bending support with constant frequency and amplitude.Our current object was the monitoring of the recrystallization, and the investigation of the influential factors of this process, but other transitions were also regarded. Those measurements’ results, that the DMTA presented, had been compared with DSC and hardness analysis, whereby we try to conclude to the utility of DMTA, in matter of metal alloys.

Abstract: Cold rolled steel specimens were investigated by color etching. We proved that in this sample ferrite grains with a surface normal close to the (111) orientation are etched with the slowest speed with Beraha-I type color etchant, and that after a sufficient over-etching these specific grains could be distinguished based on this feature. It was demonstrated, that it is possible to stop the color etching in a phase when only grains with (111) orientation show color due to the layer interference, while all the other grains are dull gray due to a thick and transparent layer. This observation was utilized to develop a method to identify and quantify ferrite grains with (111) orientation in cold rolled steel samples with the application of color etching, optical microscopy and digital image post-processing.

Abstract: An innovative X-ray diffractometer especially designed for residual stress measurements was deployed at the Institute of Physical Metallurgy, Metalforming and Nanotechnology of the University of Miskolc. The advantages of the equipment over the traditional X-ray diffraction stress measuring methods are presented through our experiences on industrial components with varying sizes, geometries and measurement requirements. The microstructural limitations of the X-ray diffraction based residual stress measurement method are also discussed.