Papers by Keyword: Light Alloys

Abstract: Laser surface treatment is at present one of up-to-date methods for surface layer engineering, in this technique into the matrix material are introduced some amount of alloying additives. So the surface layer is obtained in form of composite material consisting of ceramic particle powders with different properties influencing the surface layer appliance possibilities. Using the technology it is possible to obtain a layer revealing a structured structure consisting of the heat affected zone (HAZ), transition zone (TZ) and remelted zone (RZ), as well as the substrate material. The laser is without cracks and defects as well as has with a slightly higher hardness value compared to the raw substrate material. The used laser power range is set in the range between 1.0 to 2.5 Kw, with the laser scan rate of the beam head in a range between 0.25-0.75 m/min, depending of the applied laser power and material used for alloying.This study was conducted to determine the effect of carbide on oxide ceramic powders addition on the microstructure and mechanical properties their changes and enhancement possibilities during a rapid solidification process of the remelted surface layer. The investigation should help to use this laser treatment technology for alloying of ceramic powder particles into the surface of light alloys, especially magnesium and aluminium. The scientific reason of this work is the usage of High Power Diode Laser (HPDL) for improvement of aluminium`s mechanical properties, especially the surface hardness and war resistance.There was found during the investigations and analysis of the results that, the obtained surface layer is without cracks and defects as well as with a relatively higher hardness compared to the raw material, after standard heat treatment. The hardness value increases according to the laser power used so that the highest power applied gives the highest hardness value in the remelted layer, similar relation can be found in the wear resistance parameters, which increases also with increasing laser power.The findings of the investigations allows to state, that the distribution of the used ceramic particles is generally satisfied, especially the carbide powder was confirmed in the alloys matrix, the particles are mainly present in the upper part of the surface layer or in the bottom zone of the remelted area. The hardness value increases in general according to the laser power used and the highest power results with the highest hardness value in the surface layer. The main aim of this work is to investigate and determine the effect of HPDL remelting and alloying on the cast Al-Si-Cu and Mg-Al-Cu cast aluminium and cast magnesium alloys micro structure for possible application in real working conditions mainly for light metal constructions as well as in many branches of the industry like automotive and rail transportation.

Abstract: The current paper deals with the application of numerical experiment of joining light alloys. Modelling and numerical simulation and finite element method in the ANSYS program were used to investigate the course of thermal cycles, the joining process of light alloys by welding. Joining process of light alloys by welding is defined as a moving point source of heat, which generates temperature fields of various kinds, depending on the time and thickness of the material being welded. The paper is therefore devoted to: Thermal energy transfer and solution to differential equation of heat conduction, Initial and boundary conditions for temperatures distribution of a moving point source of heat, Generation (definition) of thermal cycle. Another part of the paper deals with the analysis of the heat-affected zone. Of the result of the solution will be expressed as the temperature field generated in the base material during the welding process.

Abstract: Light alloys are a very interesting challenge in order to have light components with high mechanical features. One of these is the 7075 aluminum alloy, which is commonly employed in aeronautic, automotive and maritime fields.On the other hand, the application of a PVD (Physical Vapor Deposition) coating can improve the hardness of the surface and the tribological properties of the component.The effectiveness of these coatings on the fatigue behavior of the sublayer material is not already clear. For this reason, bending tests on uncoated and coated specimens in air were performed in order to evaluate the S-N diagrams

Abstract: The Small Punch Creep test has proven to be a suitable technique for assessing the properties of in-service components. It is a reliable, efficient and cost-effective test for predicting the behaviour of the material. The aim of this paper is to analyse the influence of different factors on the Small Punch Creep (SPC) tests. The influence of the specimen clamping has been studied, experimentally and by means of finite element models on different materials. In the analysed conditions, it has been proven that the influence of the upper die on the tests results is generally relatively insignificant, even in the absence of upper die.Furthermore, the use of different materials at the punch has also been analysed. In order to achieve this goal, SPC tests have been carried out on two light alloys (AZ31 and AlSi9Cu3) at 473 and 523 K. Three different balls have been employed: ceramic, tungsten-carbide and steel balls. It has been proven that for the creep ductile alloy (AZ31), there is no apparent effect on the specimen response. On the other hand, for the creep brittle alloy (AlSi9Cu3), a different trend of the material response is shown, dependent on the ball used. As a result, there seems to be a significant influence of the friction between the punch and the specimen on the tests results, related to the material behaviour.

Abstract: The development and application of low density alloys, such as Al and Mg alloys, has rapidly increased in the automotive sector in recent years. This necessitates advanced characterization techniques to assess the evolution of microstructure and phases during casting and processing. Further, understanding the mechanism of evolution of the defects is important in ensuring their minimization. Neutron diffraction has provided a method to determine the factors that trigger hot tearing in Al and Mg alloys as well as determining factors compromising integrity of powertrain components. In addition, neutron diffraction has been applied to examine the phase evolution during solidification of Al and Mg alloys enabling a better understanding of the effect of inoculants and solute additions on the solidification characteristics, resulting in improved castability. This paper highlights the frontiers of neutron diffraction analysis undertaken by the Centre for Near-Net-Shape Processing of Materials, Ryerson University and the CNL-Canadian Neutron Beam Centre.

Abstract: In this paper, some recent developments in materials applied in sheet metal forming processes will be overviewed mainly from the viewpoint of automotive industry as one of the most important application fields. If we consider the main requirements in the automotive industry we can state that there are very contradictory demands on developments. Better performance with lower consumption and lower harmful emission, more safety and comfort are hardly available simultaneously with conventional materials and conventional manufacturing processes. These requirements are the main driving forces behind the material and technological developments in sheet metal forming: application of high strength steels, low weight light alloys and the appropriate non-conventional forming processes are the main target fields of developments summarized in this paper.

Abstract: Aluminum alloys are widely used in aerospace, automotive, railway and shipbuilding industry, as materials having remarkable properties for applications in these fields. For this reason, in recent years the interest for friction stir lap welding of sheets from these alloys increased.The behaviour of welding materials from the plastic and mechanic viewpoint are different in case of friction stir lap welding compared to friction stir butt welding.The welding tools for friction stir lap welding can have different configurations and sizes compared to butt welding. The used welding parameters must be reconsidered in order to obtain a proper flow of material for obtaining a friction stir lap welded joint.In addition, it is very important how to prepare the sheets surfaces that come into contact and their placement (relative to each other).The paper presents considerations regarding friction stir lap welding, with examples/concrete results obtained in welding of similar and dissimilar light alloys (alloys of aluminum, magnesium and titanium). It also presents data on the characteristics of obtained welded joints, related with particularities of friction stir lap welding.The obtained results showed that light alloys sheets used in various industrial fields can be joined with respect of basis conditions specific for the friction stir lap welding process.

Abstract: In this work a method, based on bulge tests performed on a blow forming equipment, for evaluating the superplastic material characteristics is proposed. The pressure imposed on the sheet and the height of the dome of the specimen during the test are used as characterizing parameters. Different pressure levels are applied subsequently in the same test and the strain rate sensitivity index is calculated starting with analytical considerations and then with an inverse approach based on a simple finite element numerical model of the test. The change of the slope in the specimen dome height curve, due to the change of the pressure, is correlated to the strain rate in the sheet. The method has been verified applying other load profiles on the sheet and good agreement has been found between experiments and numerical results obtained by the inverse analysis.

Abstract: Nanostructured aluminum powders were obtained by means of planetary ball milling with methanol as the Process Control Agent (PCA). The behavior, during milling, was considered measuring the microhardness and grain size at different milling times. Bulk near-full density samples were sintered using the Spark Plasma Sintering technology with different schedules: temperature of 500°C and 550°C, pressure of 30 MPa and 60 MPa and different modes of applying the pressure were changed in order to understand the behavior during sintering. The samples sintered at 500°C showed a density of about 2.4-2.61 g/cm3 while for that sintered at 550°C it was 2.65-2.67 g/cm3 depending on the applied pressure. All the samples retained their nanostructure with an increase of the grain size from about 46 up to 70-90 nm. Using X-ray diffraction and metallography the formation of Al4C3 carbides was detected for samples sintered at highest temperatures.

Abstract: Most of the work reported at this conference concerned the semi-solid processing of low melting point alloys, and in particular light alloys of aluminum and magnesium. Mg alloys are very attractive as structural materials, because they are the lightest metal among all structural metal materials and excellent specific strength. The purpose of this paper is to develop a semi-solid microstructure of Mg alloys using electromagnetic stirring applicable for lighter automobile. The size of primary solid particle and the degree of sphericity as a function of the variation in cooling rate, stirring speed, and holding time were observed. By applying electromagnetic stirring, primary solid particles became finer and rounder relative to as-cast sample. As the input Hz increased from 10Hz to 14Hz, particle size decreased. The size of primary solid particle was found to be decreased with increasing cooling rate. Also, it decreased with stirring up to 3 minutes but increased above that point. The degree of sphericity became closer to be 1 with hold time. Semi-solid microstructure of Mg alloys, one of the low melting point alloys, could be controlled by electromagnetic stirring.