Solid State Phenomena Vol. 332

Abstract: Genome engineering is a powerful tool that enhances the accelerated innovation in materials development allowing both the discovery and optimization of functionalities based on a wide range of techniques. Thin films engineering is in the forefront of this new approach by allowing the generation of a wide range of compositions in a limited number of experiments and taking advantage out of the possibility to use high-throughput characterization techniques. The paper exemplifies the innovation via compositional spreads generated by magnetron sputtering and the mapping of the material’s manufactured libraries via electric resistivity and interfacial contact resistance measurements.

Abstract: An effective way to improve quality of metal layers of the 450Kh30M and 500Kh22B7 types by controlling the silicon content in hard-facing consumables is shown. The influence of silicon and aluminum content in hard-facing consumables on content of silicon, aluminum, chromium and carbon in the hard-faced layer as well as the amount of non-metallic inclusions of silicate type was studied to develop mathematical models and to derive corresponding dependencies. As a result some corrections to the composition of the hard-facing consumables were proposed to improve quality of metal layers of high-alloyed white cast irons of the investigated types.

Abstract: Aluminium metal matrix composites (AMC) are perspective materials for a wide range of applications in automotive, aerospace and other industries where material mechanical properties and weight ratio is crucial. In AMC manufacturing through metallurgical process the main obstacle for particle introduction into the melt is poor particle wettability and their tendency to form agglomerates due to van der Waals and interfacial forces. Most of currently used AMC manufacturing methods through metallurgical route are effective only for small quantities or are time consuming, even though metallurgical AMC production route would promise significant cost savings. In this study we propose a permanent magnet stirring technology developed by IP UL as tool for alternative realization of stir- and compo-casting methods for AMC production. First results of contactless stirred semi-solid aluminium alloys show effective alloy stirring in melt volume and intense surface deformations that can break the oxide layer and stir in the reinforcement material from the melt surface.

Abstract: This paper aims to highlight the advantages of using the ultrasonic welding process to join Cu alloy connector with Cu conductor wire, materials that are widely used in the automotive industry. Ultrasonic welding is a “cold”, ecological joining process, which does not produce noxious substances and is of great interest for subassembly manufacturers operating in today’s circular economy. In order to optimize the functional parameters for the connector and conductor wire in question, we use a sonotrode (active tool) made of tool steel, at the operating frequency of 20kHz, designed and executed in INCD ISIM Timișoara; experiments were undertaken to define the welding technology parameters for the materials subjected to the experimental investigation. The results were interpreted after the execution of NDT and destructive tests, namely: visual analysis, microscopic and macroscopic investigations; hardness tests.

Abstract: In many cases it is considered appropriate to estimate, as accurately as possible, the remaining life for various metal constructions, especially when they are of major importance. By estimating as accurately as possible, the risks of yielding during operation, or even causing catastrophes, can be reduced. In order to make this estimate, various investigations are needed on the critical areas established in initial design, or determined during operation. Out of the desire to find ways to improve the procedures applied and to provide more certainty to the conclusions resulting from the technical reports prepared, the paper presents and critically analyzes such a procedure applied to a specific case. Following the analysis, several observations and technical and methodological proposals for improvement are presented, in line with current scientific and technological developments.

Abstract: In the automotive industry and not only, more and more attempts are being made to replace parts made of metals with those made of plastics, due to their low weight and low manufacturing cost. Thus, a detailed knowledge of the mechanical properties of polymeric materials is a must. This paper presents a study of the influence of temperature on the tensile mechanical properties of semicrystalline polyphthalamide (PPA). Dog bone specimens were obtained by injection molding and, in order to eliminate the possible moisture absorbed in the place of storage of the specimens, they were subjected to a drying treatment in an airtight oven at a temperature of 80 degrees for 12 hours. The specimens were tested at 5 different temperatures (25, 40, 80, 120, and 160°C) with a loading speed of 5 mm/min. For each test temperature 3 specimens were used, according to the ISO 527-2 standard. With the data extracted from the experimental tests, the mechanical properties were calculated. Also, the force – displacement and stress – strain curves were plotted. After the experimental tests, it was concluded that the dry specimens are more resistant, and with increasing temperature, the PPA material changes from a brittle to a ductile behavior. Moreover, the main tensile properties decrease significantly with increasing temperature (the modulus of elasticity decreases by 66.8% from temperature of 25 °C to temperature of 160 °C).

Abstract: The welding of shape-memory alloys is a challenge due to the fact that there are numerous compositions and because the properties are greatly influenced by the temperature. Of the multitude of shape-memory alloy systems, the most popular and widely used is the Ni-Ti system. Pulsed laser welding is a solution used for joining NiTi shape-memory alloys, having the advantage of localized heating and the possibility to adjust the welding parameters to obtain optimal properties. NiTi wires were welded using a 500W pulsed laser equipment by varying the current intensity. Thus, laser melted spots were made on a NiTi wire, changing only the value of current intensity in 20A increments in the range of 100-200A. The results analyzed by scanning electron microscopy showed, as expected, that as the current intensity increased, the spot size and the heat affected zone (HAZ) increased for each spot. Differential scanning calorimetry revealed that the martensitic transformation is still present in all samples, but with a decrease in peaks related to the phase transformation, as well as an increase of the temperature (8-12 °C), compared to the base material.

Abstract: Shape memory alloy film-based micro-actuators have their behaviour controlled by a change in the thermomechanical stress that occurs in the bimorph - shape memory alloy film plus substrate assembly. The modification of the composition of the shape memory alloy leads to a change of the transformation temperature and implicitly of the temperature at which the stress change takes place in the bimorph. The design of micro-actuator blocks in which the composition and/or the temperature control mode of each micro-actuator in the block allows to obtain successive or sequential transformation sequences. The paper analyses the case of cantilever actuator modules with films of different compositions, deposited on the same substrate. It is highlighted how the composition of the alloy film with shape memory influences the modification of the curvature of bimorph cantilever type actuators in the studied block.

Abstract: The review article describes the recent progress on SiC single-crystal and epitaxial growth technology. SiC is a third-generation semiconducting material with wide bandgap and high electrical breakdown field. Thanks to its excellent properties, it becomes an advantageous material in the field of high-temperature and high-power electronic device applications. Power devices fabricated of SiC are able to be operated at higher power density and higher switching frequency. This review focus on the growth, doping control and defect control of SiC single-crystal ingot and epilayer. The process of PVT, CVD, defect control, doping control and some recent applications of SiC are described. Various types of defects are described, including Micropipes, Dislocations, Stacking Faults etc. The wafering and polishing technology are also described.