Materials Science Forum Vol. 1095

Abstract: In the last few years, materials that may have favorable thermoelectric properties have aroused great interest, because they have the ability to generate electricity through the thermoelectric effect. In this work, the temperature effect on the transport properties of a ZnSb compound having an orthorhombic structure is studied, using the local density approximation with the modified approach of Becke and Johnson (LDA + mBJ), within the framework of density functional theory (DFT). To do this, we use the BoltzTrap package implemented in the Wien2k code, with a constant relaxation time of the charge carriers. All transport properties were studied in the temperature range of 300 to 600 K. Moreover, for high temperatures, the prediction of the figure of merit of ZnSb indicates that the compound is much more suitable for thermoelectric devices. Also, the Pauli magnetic susceptibility of zinc antimonide showed that this material is non-magnetic.

Abstract: The interaction between phonons and localized plasmons in film-coupled nanoparticles designs can be exploited both for modulating the scattered electromagnetic field and the understanding of the mechanical vibrations at nanoscale. In this paper, we show by finite element numerical analysis an enhanced optomechanical interaction in a film-coupled gold nanoridges or pillars mediated by surface acoustic waves. The metallic nanoparticles are placed atop a multilayer structure consisting of a thin dielectric spacer covering a gold film layer on a silicon dioxide/or silicon substrate. Optical simulations reveal the existence of surface localized plasmons in the infrared range confined under the nanoparticles in the dielectric spacer and/or in between such particles. Optomechanical coupling between the plasmonic modes and localized phonons is evaluated from the shift in the plasmon eigenfrequency. It is found that the compressional, the in-phase compressional and the out-of-phase flexural modes, yield the highest coupling rates. Such phonons are excited by means of SAW launched from the system inlet in front of the particles. The findings in this paper could help design new generation of acousto-optic modulators monitored by fast coherent surface acoustics.

Abstract: In this work, we present the results of the calculation of the electronic and optical properties of titanium dichalcogenide materials TiX₂ (X=S, Se, Te). These calculations were performed using the QUANTUM-ESPRESSO package, based on the density functional theory and the pseudopotential technique. The results obtained showed that TiS₂ is a semi-metallic compound, this character is due to a very small overlap between the density of states p-orbitals of S and d-orbitals of the Ti atom in the vicinity of the Fermi level. While TiSe₂ and TiTe₂ indicate the metallic characters. At the Fermi level, the total density of states is 0.77 states/eV and 1.13 states/eV for both compounds respectively. On the other hand, the optical properties of these materials such as the real and imaginary parts of dielectric function ε₁ and ε₂, respectively, the refractive index, the absorption, the reflectivity, and the loss function were investigated based on Kramers-Kroning relations in the energy range of 0 to 20 eV. In the infrared region, the reflectivity spectrum R(ω) is close to 100% for TiX₂ (X= S, Se, Te), suggesting their potential application as a good coating material.

Abstract: To meet the demands of higher speeds, higher power density and the ability to adapt to harsh operating environments over a long period of time, structural designers use various materials to fabricate rotor parts for turbine assemblies. This introduces high requirements for stable rotation and rotor life. It is therefore important to analyse and determine the mechanical properties for a turbine rotor taking into account the manufacturing process. This paper focuses on laboratory mechanical testing for determination and analysis of turbine components consisting of a rotor, from 42CrMo4 (DIN EN 10083-3) and a turbine, made from Inconel 713C in laser welded assembly. The tests carried out consists of tensile testing for the turbine – rotor assembly, microhardness measurements, macro and microscopic examinations of the welded joint. The obtained results stand as a validation for the welding process technology used for this type of application ensuring the superior mechanical characteristics required for operation in harsh enviornments.

Abstract: The article presents experiments for the development of the welding technology for plates of the steel S355JR, according to EN 10025-2:2004, for ship building and harbor structures.Marine steel plate grades for ship hull, according to ABS, American Bureau of Shipping, are presented, compared with the S355JR steel.For applications on board ships, the standard EN ISO 5778:1998 is also mentioned. It specifies the materials and quality levels for small weathertight steel hatches.The filler metal is the copper-coated, manganese-silicon-alloyed solid wire, type SG-3, according to EN ISO 14341:2020. The shielding gas is the gas mixture CORGON 18/82, according to EN ISO 14175:2008, type M21.As a welding travel unit, the modular drive system MDS-1, made by the company BUG-O Systems, of USA was used. It has the following main components: 1- rack-based track; 2- carriage; 3- master drive unit; 4- clutch; 5- weaver control module; 6- linear weaver unit; 7- linear weaver cross arm; 8- gun mounting group; 9- welding gun.The welding source is the Inverter MIG 300 A type, manufactured by Mahe GmbH, Germany.The sizes of the two plates for the welding test piece are: length 700 mm; width 200 mm; thickness 15 mm, I groove with 8 mm gap.The welding parameters used for all the layers (root, fill #1 - fill #4) are presented in a common table, for comparison.The parameter ranges are as follows: welding current 177-251 A; welding voltage 21.9-23.1 V; wire advance speed 6.5-7.2 m/min; shielding gas flow rate 20.8-21.8 liters/min; welding speed 20-45 cm/min. A special spin-arc welding method was applied on all weld layers. The execution of the welding test piece is described with specific details and photos.Upon visual inspection after the execution of each layer, the appearance is adequate. No defects or imperfections are observed.On ultrasonic examination, the results are adequate.Metallographic examination, tensile, bending and Charpy V impact tests are presented with appropriate results.The conclusions mention the adequate results obtained, regarding the ranges of the welding parameters and the use of the innovative spin-arc technology. Possible applications of the S355JR steel are recommended.The references present titles related to ship building steels, filler metal, shielding gas, welding equipment and some specific technologies.

Abstract: The article presents the development of a gas-metal-arc welding technology with spin-arc and weaving facilities, for 15 mm thick plates of the steel S355J2+N, according to EN 10025-3: 2019, for shipbuilding and harbor structures construction.The filler metal is the manganese-silicon-alloyed solid wire, type SG-3, according to EN ISO 14341:2020. Shielding gas is mixture CORGON 18/82, type M21, according to EN ISO 14175:2008.The modular drive system MDS-1, manufactured by the company BUG-O Systems, of USA was used. Among other main components, it has a linear weaver unit and a weaver control module.The welding source is the Inverter MIG 300 A type, manufactured by Mahe GmbH, Germany.This welding source is connected with both a spin-arc module and a welding gun, made by the company WeldRevolution of USA. This spin-arc-weaving technology is intended to reduce the welding process duration, filler metal and energy consumption, respectively to increase the productivity by means of both the spin-arc and weaving features of the combined welding equipment.The sizes of the two plates for the welding test piece are: length 370 mm; width 200 mm; thickness 15 mm, I groove with 8 mm gap. This narrow groove preparation is also expected to have a contribution to the reduction of the necessary filler material.The parameter ranges are as follows: arc voltage U_a = 21.7- 23.5 V; welding current I_s = 183- 225 A; wire advance speed v_e = 6.5- 7.2 m/min; shielding gas flow rate f_g = 20.5- 22.0 liters/min; welding speed v_s = 20 - 35 cm/min; spinning diameter range d_s = 1 - 8 mm, selected diameter d_r = 3 mm (3 divisions); rotational speed of the spin-arc v_sa = 1500 rotations/min, selected from the range 750- 7500 rotations/min; angular weaving mode; weaving speed (frequency) v_p = 2.5 – 5.0 divisions; weaving amplitude a_p = 1 – 2 divisions; dwell time t_f = 2.0 divisions.After the execution of each layer, the appearance is adequate. No defects or imperfections are found. On ultrasonic examination, the results are adequate. Metallographic examination, tensile tests and Charpy V impact tests have accepted results.The conclusions describe the adequate results obtained, regarding the ranges of the spin-arc and weaving parameters. Possible applications of the S355J2+N steel are recommended.The references cite articles related to welding of ship components, including some spin-arc and weaving equipment.

Abstract: Ultrasonic welding is an environmentally friendly, nontoxic welding process preferred by top industrial manufacturers and in accord with the European circular economy regulation. Ultrasonic welding is an environmentally friendly, nontoxic welding process preferred by top industrial manufacturers and in accord with the European circular economy regulation. This scientific article analyses the ultrasonic welding behaviour of composites fabricated by additive manufacture technology using reinforcements, such as: glass fibre, Kevlar, Cu wire, etc. These materials are organized in a „sandwich” structure with different reinforcements and welded by ultrasound. Results were interpreted and compared with base material after performing NDT and destructive tests, namely: visual analysis, microscopic and macroscopic investigations: tensile tests, hardness tests, bending tests.

Abstract: Ni-based metallic amorphous alloys in ribbons shape are used in the manufacture of electrical resistances due to their high electrical resistivity, a value that does not change with temperature. The production of such resistances involves joining processes of amorphous ribbons. The amorphous alloys are difficult to weld by conventional melting processes, even in the presence of inert gas. Consequently, this paper presents the research carried out regarding the capacitor energy storage welding technique of Ni₆₃Cr₁₂Fe₄Si₈B₁₃ amorphous ribbons. The structural analysis was done by microscopy, X-ray diffraction, and differential scanning calorimetry, and the mechanical behavior was determined by nanoindentation. The joints obtained showed that the proposed welding technology is appropriate for this type of joint.

Abstract: The application of high-strength steels is increasing rapidly nowadays, and steels with more than 1000 MPa yield strength are usually used in welded structures. The welding of these materials has many difficulties, so very important the precise technology planning, and disciplined work during welding. The weldability of these materials is commonly investigated field in case of joining. The application of ultra-high strength steels expands rapidly, and in the last years, it started to use them as a base material for hardfacing. Besides the wearing, there is a claim about higher strength of base materials in case of relatively extremely loaded machines. Because this ultra-high strength steel appears as a base material for hardfacing and it brings new challenges for welding technologists. In case of joining, the welding technology is complicated, usually need preheating before welding, is important to calculate and to use the right t_8/5 cooling time, and basically necessary to decrease the heat input as much as possible. The bad effect of welding heat input can be compensated by the filler material too in some cases. In contrast in case of hardfacing the base material itself usually has a big thickness, and no joint preparation, additionally important to reach deep fusion on the surface. It basically determines the heat input which has a different heat cycle as in case of joining. Therefore, the heat affected zone (HAZ) differs from the HAZ in case of joining application. In this investigation, four different hardfacing were made with four different technological parameters by robotic gas metal arc welding on S1100QL steel. During the welding parameter determination, we try to find a series of heat inputs from the lowest to the practically usable highest heat input. For the experiments, two filler materials used, one for the buffer zone, and for the hardfacing itself. Microstructural evaluation and hardness tests were made on the specimens which can show the differences between the heat affected zones.