Materials Science Forum Vol. 812

Abstract: Surface quality development on series of metal samples was investigated using a new Ar ion milling apparatus. The surface quality of samples was characterized by the image quality (IQ) parameter of the electron backscatter diffraction (EBSD) measurement. Ar ion polishing recipes have provided to prepare a surface appropriate for high quality EBSD mapping. The initial surfaces of samples were roughly grinded and polished. High quality surface smoothness could be achieved during the subsequent Ar ion polishing treatment. The optimal angles of Ar ion incidence and the polishing times were determined for several materials.

Abstract: It have been studied the cold rolling effects on the microstructure of samples prepared from Al-killed low carbon steel sheets with high coiling temperatures. The microstructure of the hot rolled steels sheet is formed from ferrite and large carbides when the coiling temperature is high. The cold rolling affects the steel mechanical and electrochemical properties due to microstructural changes. We have studied the microstructure by optical microscope and scanning electron microscope. Low angles grain boundaries and the texture of samples were studied by EBSD method.

Abstract: Technological residual stresses have great importance in the manufacturing processes and the lifetime of components. The residual stresses formed by quenching can be very diverse because of its multiple sources. Alternative quenching processes such as laser hardening have a great potential for different applications. The direction of heat transfer during laser hardening is the opposite compared to conventional quenching. This further increases the complexity of the developed stress state. The residual stress profile and the microstructure formed by laser hardening treatment are investigated in the present manuscript.

Abstract: Nanostructured silver layer was deposited by pulse current technique onto three different implant materials-TiAl6V4, CoCrMo alloy and stainless steel–that are commonly used in orthopedic surgery. The electrochemical behavior of the coatings in isotonic salt solution was investigated by potentiodynamic polarization measurements over a period of several weeks. The corrosion properties of silver coated different implant materials were compared. Degradation of silver coatings have been traced and confirmed by different methods such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) measurements.

Abstract: In this study the possibility to apply electrochemical impedance spectroscopy as an alternative method for the characterisation of the intermetallic microstructures of Sn-3.5Ag lead free solder samples was investigated. The aim of the study is to compare the electrochemical impedance spectra of solder samples, reflowed with different heat profiles. A quenching technique was applied in order to solidify the solder samples in cylindrical crucibles. Differences in the microstructures of the solidified alloys were achieved by changing the temperature of the quenching media. The molded and cross sectioned specimens were observed using both optical microscopy and scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS). The microstructure of the ingots was revealed by selective electrochemical etching. The electrochemical impedance spectrum (EIS) was measured before and also after the selective etching process. The complex impedance spectra contain information regarding the characterized microstructure. Our aim is to determine quantitative parameters which are identical to the characteristics of the microstructure.

Abstract: In case of titanium dental implants, the main goal is to create a surface where the bone cells can attach well, therefore osseointegration can occur. The chemical composition of the surface has an important role, because the surface has a direct contact with the living tissue and induces different reactions for example peri implantitis or osseointegration. In our work titanium sample made from the most commonly used dental implant material (Ti Grade 5) were investigated. The samples were treated by chemical etching in hydrogen-chloride and in phosphoric acid to remove the cut generated burr. After that the samples were anodized in phosphoric acid solution at 10 V, 20 V, 30 V or 40 V. As a result of these treatments, titanium-dioxide layers were created on the surfaces. Phosphorus (originating from the phosphoric acid bath) may also be found on the surfaces. This may promote osseointegration. The surface compositions were investigated with the aid of Secondary Ion Mass Spectrometry (SIMS). Based on these results we can conclude that anodization in phosphoric acid solution increases the phosphorus content of the surface. Approximately to the middle of the titanium-dioxide layer the phosphorus content is constant but lower with one order of magnitude than on the surface. In the deeper layers the phosphorus content continues to decrease until the base material where it significantly reduce.

Abstract: One of the most critical parts of the heat treatment process, and usually the least controllable one, is the quenching operation. Improper selection or application of a quenching medium, or a drift in its cooling characteristics during its lifetime, may result in products that do not meet specifications and therefore give rise to large additional costs to cover e.g. straightening, rework, rejection, delayed deliveries and, sometimes, lost goodwill for the heat treater. In the case of the use of aqueous polymer solutions, the thermo-kinetic parameters characterizing the heat removal capabilities of a quenchant, are variable, in a specific interval with a complex combination of temperatures (T), concentrations (C) and agitation rates (AR). When the direction and degree of change is known, the characteristics of heat removal can be efficiently modified and predicted within given limits. The aim of the work described in this paper is to investigate how the hardening power of Houghton AquaQuench BW-T depends on the complex influence and interaction of T, C and AR.

Abstract: Nowadays, there is increasing importance of the remaining life time estimation of engineering structures. In this work the thermal fatigue process induced deterioration of the three different power plant steels was investigated. The tested steels are widely used as steam pipeline base material of power plants. The applied thermal fatigue test can model the material degradation due to long term service in high temperature environment. In this paper a new high sensitivity magnetic measuring technique is presented called Adaptive Nonlinear Harmonic (ANLH) method. The sensitivity of this measurement is optimized for controlling the thermal fatigue deterioration. The presented novel measurement was developed for non-destructive testing of pipelines and pressure vessels of power plants.

Abstract: Industry should gradually replace the tin-lead solder alloys used traditionally in the soft soldering technology by lead-free soldering alloys, which raises a lot of new technological and scientific problems to be solved. The introduction and application of lead-free alloys caused a number of soldering defects not observed earlier; mechanisms of their formation are still unclear. One of such defects is whisker formation, another one is intensified formation of intermetallic phases. The appearance of undesired intermetallic phases in the soldering material spoils its mechanical properties; therefore it is particularly important that these phases do not form in electronic components. Besides, the formation of intermetallic compounds may occur in the soldering bath, thus making the soldering process difficult or even impossible.Tin-copper-nickel and tin-silver-copper alloys are suitable for the replacement of tin-lead alloys. The components of these alloys were studied. After metallographic examination of the specimens the occurrence of intermetallic phases was determined by the XRD method. The identification of intermetallic phases was carried out by using literature data and phase diagrams.

Abstract: The purpose of our research was the development of a new algorithm to the objective quantification of guidewire’s visibility; which is suitable for the classification and comparison of different guidewires, according to this property. The guidewire is a flexible medical device, over which the catheter or the dilator is lead into the vascular system to assist the insertion and position of these devices. During the insertion and the removal of guidewire the movement of distal end is monitored under fluoroscopy. At the beginning of our experiments two algorithms were developed and applied: the first one investigated the total distal end, while the second one investigated two parts of the distal end. Both algorithms were tested on ten guidewires made of same brand and material, so their relative visibility (the visibility of guidewire’s investigated part compared the background) were determined by both method. The average relative visibility was 19.8%±3.0% in case of algorithm for total distal end, and it was 21.5%±2.9% in case of algorithm for two part of distal end. The coefficient of variation was calculated in case of both algorithms, thus characterized by their reliability. Both coefficient of variation were low (0.15 and 0.13), so the algorithms were considered to be reliable. The two algorithm were no significant different (p=0.15), therefore the investigation of the total distal end might be replaced by the investigation of two parts.