Materials Engineering - Materiálové inžinierstvo (MEMI)
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The influence of heat treatment on properties of lead-free solders
Get PDFThe article is focused on the analysis of degradation of properties of two eutectic lead-free solders SnCu0.7 and SnAg3.5Cu0.7. The microstructures of the intermetallic compound (IMC) layers at the copper substrate - solder interface were examined before and after heat treatment at 150°C for 50, 200, 500 and 1000 hours. The thickness of IMC layers of the Cu6Sn5 phase was growing with the increasing time of annealing and shown the typical scallops. For the heat treatment times of 200 hours and longer, the Cu3Sn IMC layers located near the Cu substrate were also observed. The experiments showed there is a link between the thickness of IMC layers and decrease of the shear strength of solder joints. In general, the joints made of the ternary solder showed higher shear strength before and after heat treatment in comparison to joints from solder SnCu0.7
Changes in mechanical properties of as-cast magnesium alloy AZ91 after equal channel angular pressing
Get PDFThis paper deals with differences in mechanical characteristics of AZ91 magnesium alloy in the as-cast state and after the subsequent equal channel angular pressing (ECAP) and with measurement of local microhardness. According to the obtained results, the tensile properties increased by a factor of two due to the ECAP procedure. The proof stress, σ0.2, increased to 160 MPa and the ultimate tensile strength, σUTS, to 321 MPa. The local microhardness of ECAPed alloy varied between 70 and 91 HV 0.025 due to microstructural bimodality.
Thermal, structure and phases analysis of the aluminium ENAC-AlMg5Si2Mn alloy
Get PDFThe microstructure that is attributable from the specific casting method dictates further mechanical and physical properties of the material. In order to understand how to control the microstructure of the casting, it is important to understand the changes in microstructure during crystallization. The work focused on thermal analysis, metallurgical characterization and laser treatment of an aluminium alloy. The research show that the thermal analysis carried out on UMSA Technology Platform is an efficient tool for collect and calculates thermal parameters. The paper contributes to better understanding non-equilibrium metallurgical characterization of aluminium alloys. The solidification of the aluminium dendritic network, iron containing intermetallic phases, the aluminium-silicon eutectic and magnesium containing intermetallic phases were characterized.
Differences in the surface texture of aggregate particles determined by 3D model derived from optic microscope measurements
Get PDFoai:ojs.pkp.sfu.ca:article/184The surface texture of aggregate particles was investigated based on the 3D model of surface generated from the measurements by optic microscope. New software MicroSYS was developed to determine the wrapping plane of 3D model of aggregate using the function called “Thin plate spline“. New parameter for evaluation of surface texture of aggregate particle was proposed as the volumetric difference between two planes (wrapping plane and aggregate surface). Applicability of this parameters was tested on two aggregate fractions (4/8 and 8/11) coming form 11 quarries in Slovakia. The tested aggregates differed from petrography point of view and ranged from soft to hard. The difference among the quarries and also between fractions of aggregate was found out. The better surface texture was observed for the finner fraction of aggregate. Simultaneously, the better results were determined in the case of aggregate produced from the ingeous intrusive or extrusive rocks comparing to the sedimentary carbonate rocks aggregate
Prediction of maximum casting defect size in MAR-M-247 alloy processed by hot isostatic pressing
Get PDFNickel based MAR-M-247 superalloy treated by hot isostatic pressing was investigated with the aim to identify the influence of casting defect size on fatigue life. Two testing temperatures of 650 and 800°C and one stress amplitude were chosen for fatigue tests. The Murakami approach and the largest extreme value distribution theory were applied. It has been found that the maximum size of casting defects in a specimen can be satisfactorily predicted. Fatigue life of specimens was in the good agreement with assumptions based on the evaluation and prediction of the casting defect size
Optimal welding technology of high strength steel S690QL
Get PDFIn this paper is presented the detailed procedure for defining the optimal technology for welding the structures made of the high strength steel S690QL. That steel belongs into a group of steels with exceptional mechanical properties. The most prominent properties are the high tensile strength and impact toughness, at room and at elevated temperatures, as well. However, this steel has a negative characteristic - proneness to appearance of cold cracks. That impedes welding and makes as an imperative to study different aspects of this steel's properties as well as those of eventual filler metal. Selection and defining of the optimal welding technology of this high strength steel is done for the purpose of preserving the favorable mechanical properties once the welded joint is realized; properties of the welded metal and the melting zone, as well as in the heat affected zone, which is the most critical zone of the welded joint
EVALUATION OF FIBRE LENGTH DISTRIBUTION IN A SHORT GLASS FIBRE REINFORCED PA-6
Get PDFThe aim of this work is to evaluate the fibre length distribution in a polyamide reinforced by short glass fibre. The fibre length and the fibre orientation distributions strongly influence the mechanical properties of short fibre reinforced composites. The sample investigated is a 30GFPA6 (polyamide-6 reinforced by 30 % by weight glass fibre), extracted from an injection-moulded plate. The digital reconstruction of the three-dimensional structure of the sample was obtained by synchrotron radiation micro-computed tomography (micro-CT), a high spatial resolution non-destructive technique. One global and one local method have been tested for the automatic evaluation of the fibre length distribution in our sample. The global method is based on the mean fibre length distribution computed from the Star Length Distribution (SLD), a morphological parameter. The local method is based on a 3D skeletonize function. The results are discussed in the light of the experimental data available in literature
The Investigation of the Corrosion Resistance of the Tension Clamps Skl14
Get PDFAt the level crossings it is possible to find the problems with the corrosion of the parts of the fastening system. These problems are especially at the rubber level crossings and in the tunnels. As a part of the thesis the problem of the corrosion of the tension clamp Skl14 of the producer Vossloh at the rubber level crossings is examined. For the purposes of the comparison the tension clamps without the corrosion protection and the tension clamps with the corrosion protection KTL were examined. As a first step the corrosion features of the tension clamps Skl14 were solved. The examination was divided into two parts. First part it was the examination according to ČSN EN ISO 9227. The samples of the tension clamps were putted into the corrosion chamber. After 1728 h the results of the corrosion impacts were not satisfied. It was decided for the second step of the examination. It was the immersion in an electrolyte solution. As a result of the paper the corrosion features of the tension clamps without the corrosion protection and with the corrosion protection are compared
CHARACTERIZATION AND PERFORMANCE OF DUPLEX-COATINGS ON Cr-V COLD WORK TOOL STEEL
Get PDFSpecimens made of Vanadis 6 steel were heat treated, plasma nitrided and coated with Cr2N. The microstructure, phase constitution and mechanical properties of plasma nitrided areas and duplex-coatings have been investigated using the light microscopy, scanning electron microscopy, X-ray diffraction and microhardness measurements. The adhesion of the coatings and the wear performance were studied using the scratch test and ring-on-plate tribological testing. Worn surfaces were examined by scanning electron microscopy. Nitrided areas formed at lower temperature were free of compound “white” layer while hose developed at higher temperatures contained as the white layer so the nitrided network. Significant increase in substrate hardness was detected due to the nitriding. Beneficial effect of the nitriding on the adhesion of Cr2N coatings was clearly determined whereas the extent in improvement of the adhesion depends on the presence/no presence of “white” layer on the surface. The extent of beneficial effect of plasma nitriding on the wear performance follows the impact of the constitution of nitrided areas on the adhesion. The amelioration of wear performance of Cr2N coatings can be attributed to the supporting effect of hard nitrided intermediate region, which provides excellent resistance of the substrate against plastic deformation, under heavy loading in particular. Practical testing demonstrated many times prolonged service-time of duplex-treated tools for sheet metal working.
ELECTROCHEMICAL METHODS TO IMPROVE THE WEAR RESISTANCE OF COATING DEPOSITED ON THE METAL SURFACE
Get PDFIt was established that existing methods show low accuracy when assessing the durability of coatings. Furthermore, they don’t allow assessment of the contribution into durability of structural components and fillers for thermodiffusion and polymer-composite coatings, respectively. A method to evaluate durability of thermal diffusion chrome coatings on carbon steel and gray cast irons has been developed - the speed υp of destruction of the structural components of the coating. In addition, the destruction of each structural component is characterized by a constant value of destruction speed υp and potential φ, and their sharp vibrations are in complete destruction of the coating and the beginning of the destruction of the base metal. From the start of the test until the abrupt change in the rate of destruction υp, which is found on the curve υp - τ is the assessment of durability coating t¶ hat is specified with the curve φ - τ. Accuracy of the durability decreases from ± 30 min to ± 2 min. Developed as a way to assess the durability fillers polymer composite coatings, along with the finding that the rate of destruction υp of the time includes total disability coverage t3aƧ and time breakdown cover τn which are fixed on the curve φ - τ.