Advanced Materials Research Vol. 1114

Abstract: The intermetallic compounds (IMC) of Ni-Al system exhibit interest both by theoretical and practical point of view: theoretically, due to particular aspects in relation to their synthesis and practically, due to their qualities that recommend them for the top industries such as, for example, the aerospace industry. In this paper are shown the results of researches on obtaining of high temperature compounds of Ni-Al system by self-propagating high temperature synthesis and thermal explosion, through the initiation of process at a temperature below the melting temperature of the easy fusible component.

Abstract: Severe plastic deformation (SPD) has received enormous interest over the last two decades as a method capable of producing fully dense and bulk ultra-fine grained (UFG) and nanocrystalline (NC) materials. Significant grain refinement obtained by SPD leads to improvement of mechanical, microstructural and physical properties. Compared to classical deformation processes, the big advantage of SPD manufacturing techniques, represented in particular by equal channel angular pressing (ECAP) is the lack of shape-change deformation and the consequent possibility to impart extremely large strain. In ECAP processing, the workpiece is pressed through a die in which two channels of equal cross-section intersect at an angle of ϕ and an additional angle of ψ define the arc of curvature at the outer point of intersection of the two channels. As a result of pressing, the sample theoretically deforms by simple shear and retains the same cross-sectional area to allow repeated pressings for several cycles. A commercial AlMgSi alloy was investigated in our study. The specimens were processed at room temperature for multiple passes, using three different ECAP dies. All samples (ECAP processed and as-received) were subjected to metallographic analysis and mechanical testing. Several correlations between the main processing parameters and the resulting microstructural aspect and mechanical features for the processed material were established. It was shown that severe plastic deformation by means of ECAP processing can be used in aluminum alloys microstructural design as an advanced tool for grain refinement in order to attain the desired microstructure and mechanical properties.

Abstract: The Ti-25Ta-25Nb alloy was produced in a levitation induction melting furnace, under argon protective atmosphere. The obtained ingots were two times remelted, in order to obtain a high degree of chemical homogeneity. The alloy was then thermo-mechanically processed by a first cold-rolling and a recrystallization treatment in a heat treatment oven, followed by a second cold-rolling, to achieve final strips of 141 μm thickness. Using a PanalyticalX’Pert PRO MRD diffractometer, the as-cast specimens and the final cold processed specimens were XRD characterized, so that the phase structure and phase characteristics could be determined. The position of each diffraction peak, the intensity and the peak broadening parameters were determined using the PEAKFIT v4.11 software package. Finally the structural features of Ti-25Ta-25Nb alloy in the as-cast state and thermo-mechanically processed state were shown and discussed.

Abstract: The paper presents results of researches carried out to establish the causes that led to the cracking of forgings made of manganese low alloy steel microalloyed with boron. The researches includes analysis of samples taken from the forgings in the cracked surface area and also analysis of a sample from forged material. The following methods and techniques were used for investigation:metallographic analysis by optical microscopy;visual macroscopic examination by scanning electron microscopy (SEM) at low magnification, using scanning electron microscope;examination by scanning electron microscopy on the material cracks area and its adjacent area;investigation of material by X-ray microanalysis in energy dispersive (EDAX) for its characterization, in terms of microcomposition;

Abstract: This paper presents in detail the laser welding of a new mechatronic component belonging to the pressure sensors made ​​by aluminum alloy AW2007. Due to very high reflectivity of aluminum alloys, fast oxidation, the absorption of gases from the surrounding medium, special difficulties arise at laser beam welding and most situations require appropriate surface pretreatment. Given these issues, the paper present an experimental study on the influence of welding parameters on the seam quality for the aluminum alloy AW2007. In addition of the study regarding the influence of welding parameters, such as, laser power, welding speed, we conducted an analysis on the influence of the initial temperature of the material on the quality of the weld. Besides these aspects the paper presents a constructive solution for a device used to optimize the laser welding process of the sensor.

Abstract: The goal of this paper is to analyze the influence of the mechanical vibrations during the casting on AlSi10Mg casting alloy structure. Seven samples were studied, solidified on vibrating field, using different frequencies and accelerations. After preparation, the structure was studied using optical microscope and SEM. The dimension of the Si phase was also measured. Through applying the vibrations during the crystallization, the fragmentation of the dendrites was accomplished by obtaining solid solution regions close to a spherical shape. These regions contain chemical compounds of a much smaller size than those resulting from static crystallization. The dimension of the Si phase is influenced by the presence of vibrations; increasing frequency will induce the decreasing of the Si phase size. The mathematical modelling of the frequency influence on the Si phase dimension is also presented.

Abstract: The electronic modules are complex ensemble of electronic components having terminals (PIN) connected by solder joints on dedicated metallic surfaces (PAD) parts of conductive interconnection structure realized on rigid or flexible dielectric substrate having different core materials. The reliability of the electronic modules could be considered as expression of solder joints functionality (SJF) relating to working conditions and unique defined by their electrical, mechanical and thermal properties. These properties are in close connection with the solder joints microstructures, result of the soldering Process temperature gradient action over the trinomial solder alloy Paste, Pin and Pad. Consequently the solder joints quality can be correctly evaluated taking into consideration not only the severally intrinsic parameters of the trinomial elements Pin-Pad-Paste characterized by specific thermophysical properties (ThP), but also interrelate the complex reaction at the interface between them and interdependence with the soldering Process parameters.In the paper, will be analyzed the influencing factors of manufacturing processes, the most important assembling defects at macro and micro level, their causes relating to specific ThP and processes at interfaces Pin-solder joints-Pad, it will be identify the Key Process Input Variables (KPIV) and propose a structural model for assembling processes, 4P Soldering Model, as an useful tool in engineering of electronic product in order to assure the assumed goal for assembling stage.

Abstract: Investigations on carburized layers phase composition are usually made ​​by optical microscopy, electron microscopy and X-ray diffraction. A microstructure consisting in different proportions of superior bainite, inferior bainite, martensite and retained austenite was found after carburizing in paste of the 21NiCrMo2 steel which has appropriate bainitic hardenability. The investigations carried out on 21NiCrMo2 steel samples, carburized in paste with additions of about 10% Ce, highlighted a significant change of phase proportions ratio in the carburized layer resulting in an important increasing of the lower bainite ratio. It was also observed, that the carburized layer case depth obtained in the carburizing paste with Ce additions does not significantly differ in relation to that attained in the carburizing paste without Ce additions but the microhardness increases considerably. The reason is connected also to the presence of Ce carbide identified by X-ray diffraction in the carburized layer. The Ce hard affinity towards oxygen and its influence on bainitic hardenability increasing is well known and adopted, however neither Ce transfer mechanism from carburizing paste to the carburizing layer and nor the effects of its high affinity to oxygen (for example) are not addressed in this particular case. The present study proposes a possible transfer mechanism of Ce in the carburized layer and an explanation of the consequences of Ce hard affinity towards oxygen on the phase composition of the carburized layer. Nanoscale iron oxides such as wüstite, magnetite and maghemite were identified in the surface of the carburized layer by Mössbauer spectrometry.

Abstract: Increasing the functional parameters and endurance of the turbines, blades systems, rocket engines, high-performance metallurgical installations, power energy require the creation of new systems for integrated assessment, testing-investigating.From the ensemble of wear factors acting simultaneously on the multilayer ceramic materials, associated to the coatings structures, the quick thermal shock acts most disruptive.To illustrate the effect of gradients with high value for heating-cooling the authors have designed and developed a versatile installation with semi-automatic functioning and monitoring test parameters. The fundamental testing parameter that the installation uses is heating-cooling speed up to 100 ° C/s, which is superior to the performances of the known testing installations.The extreme thermal shock testing parameters generate in the multilayers ceramic structures, triplex type with intermediate layer, structural, morphological and composition modifications which initiate and develop the ceramic layer spallation.

Abstract: Hardfacing can be broadly defined as the application of a wear-resistant material, in depth, to the vulnerable (or worn) surfaces of a component by a weld overlay or thermal spray process.In the paper are presented the main hard facing iron-base and nonferrous alloys together with their properties and applications, together with a comparison of its performances.In addition, hardfacing alloys are applied to critical wear areas of original equipment or during reclamation of parts. These alloys, which are referred to as buildup alloys, are not designed to resist wear but to return a worn part beck to, or near, its original dimensions and/or to provide adequate support for subsequent layers of more wear-resistant hardfacing alloys.