Solid State Phenomena Vol. 349

Abstract: Ti-6Al-4V alloy is not easy to machine complicated shapes due to its low thermal conductivity, so high-temperature forming techniques such as ring-rolling are being applied. When this high-temperature forming technology is applied, the microstructure is greatly changed by process variables, and the mechanical properties of the forming product are also different accordingly. In particular, in the case of the Widmanst tten structure, α lamellar spacing and colony size have a great influence on mechanical properties. Therefore, in this study, the most suitable process conditions were selected by performing a high-temperature compression test to apply the ring-rolling process to the Ti-6Al-4V alloy used as an aerospace material. After that, the microstructure of the forming product was observed, the effects of α lamellar spacing and colony size on the mechanical properties were confirmed, and the correlation between mechanical properties and microstructure was evaluated based on this.

Abstract: Friction stir welding (FSW) has become very popular for joining similar or dissimilar aluminum alloys. The heat used for this welding process is caused by friction between the welding tool and the workpiece which the axial force, the main parameter for heat generation, plays a very important role. Insufficient heat during welding will result in defective workpieces. This research is aimed to predict the axial force from the relevant factors of the FSW of dissimilar materials (aluminum alloys AA2024-T3 and AA6061-T6). The 2³ full factorial design with center point was used for this experiment that consisted of 3 main factors: 1) rotation speed (rpm), 2) welding speed (mm/min), and 3) pin geometry each factor has 2 levels and 2 replications with the total of 20 experiments. The axial force data of each experiment were collected using a stationary dynamometer which obtained the data acquisition every 0.1 seconds (frequency of 10 Hz). The results from the design of experiment were analyzed by statistical method at the significance level of α = 0.05 which found that the significance and the optimum value of the main factors were rotation speed of 1500 rpm, welding speed of 35 mm/min, pin geometry of tri flat threaded, and the 2-way interaction between rotation speed and pin geometry. Furthermore, the prediction of the average axial force value on dissimilar aluminum alloys obtained from the specified parameters equals 478.91 N.

Abstract: The wire arc additive manufacturing (WAAM) technology has become very popular recently. However, the properties of printed pieces are not yet examined properly. In this paper the effect of severe shot peening (SSP) on mechanical properties of wire arc additive manufactured AISI 316L is investigated. The effect of SSP on the surface hardness of the WAAM 316L is investigated by performing microhardness measurements. Changes to the surface microstructure caused by SSP are evaluated in the EBSD investigation. The effects of SSP on tensile and fatigue strength are investigated experimentally. The EBSD analysis showed that there has been remelting of each printed layer due to the heat input from the next printed layer, and heavy epitaxial grain growth was present in the microstructure. This led to coarse columnar grain structure. Investigation of deformed SSP surface layer indicated that the main deformation type was either conventional dislocation glide or twinning. This meant that no martensite formation was present on the surface. The SSP increased the surface hardness of WAAM printed 316L by 225% and the hardened layer was 0.4 mm thick. The SSP improved the yield strength of WAAM 316L by 34%. The SSP significantly improved WAAM 316L fatigue resistance in both low-cycle and high-cycle regime.

Abstract: Beta stabilizing elements cause high processing cost due to their high density and high melting point. Ti-xMo-2Fe alloy is metastable beta titanium alloy containing a low-cost beta stabilizing elements, and it is possible to secure excellent price competitiveness. Microstructure characterization and mechanical properties of a new designed Ti-xMo-2Fe alloys were investigated by Optical microscope, Vickers hardness, room temperature tensile test, in this study. The microstructure and mechanical properties were different depending on Mo contents, and Ti-9.2Mo-2Fe showed high hardness and brittle failure due to the high Mo content. As a result, Ti-3.4Mo-2Fe showed a tensile strength of 821.2 MPa and a high elongation of 10.3%.

Abstract: The incremental sheet forming process (ISF) is the emerging forming process in the small size product manufacturing industries where as embossing, stamping, coining operations can be used to produce a product in large quantity. Therefore, ISF is one of the best solution to decrease the cost of production when a small quantity of product is demanded. In present study Efforts are devoted to study the effect of wall angle on sheet thinning, reaction forces, reaction moments, etc. for truncated cone of aluminium alloy (AA1050) using Finite Element simulation. Initially, A MATLAB code was written for spiral tool path. Modeling and simulation was done in ABAQUS software. Thereafter, a theoretical sheet thickness was computed using sine law and it was found out to be in close agreement with simulated sheet thickness.

Abstract: This research aims to study the influence of controlled parameters on the machining performance for small hole drilling by an electrical discharge machine. Tubular copper with an outside diameter of 1 mm was used as an electrode. JIS SKD 61 grade steel at a depth of 40 mm for machining was used as a workpiece. The experimental results show that machining speed and electrode wear drastically increased with the discharge current. The high machining performance with varied pulse on-time occurred in the range of 16 to 28 μs. The machining time and electrode wear ratio increased with a decreased pulse off-time. In addition, the lowest difference in the dimension of the entrance and exit of the drilled hole at approximately 0.030 mm appeared at the pulse off-time of 6 μs. However, the high machining speed and electrode wear ratio occurred at the low dielectric pressure of 20 kg/cm². Furthermore, the machining performance reduced and slightly fluctuated with the varied dielectric pressure in the range of 40 to 80 kg/cm².

Abstract: This paper presents the results of factorial experiment applied to optimize Matrix‑Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition (PLD) coating technologies used to improve the corrosion resistance of steels. MnTa₂O₆ pseudo-binary oxides and 5,10-(4-carboxy-phenyl)-15,20-(4-phenoxy-phenyl)-porphyrin was used for these experiments to obtained thin film coating system of hybrid nanostructures. Based on factorial experiments, correlations between the main technological parameters of the coating process (MAPLE laser energy E_MAPLE [mJ], PLD laser energy E_PLD [mJ]) and porphyrin concentration and the main related property of the coating system (corrosion protection factor) were determined. The base material used as substrate in the experiments was S235JR+C. Electrochemical measurements showed that by applying the appropriate parameters of the coating technologies, homogeneous layered sandwich thin films were obtained and corrosion rate was reduced by more than 7 times.

Abstract: The good mechanical properties of aluminum alloy 2017 A have determined its use in a wide range of applications in which cavitational solocitations occur, such as hydraulic actuation installations, heat engine blocks, boat propellers and sloops, pumps in the cooling system of thermal engines, wings and ogives of airplanes. Currently, research is focused on the development of procedures for improving the resistance to cavitational erosion of these materials. This paper presents the results of the research on the cavitation erosion behavior of the material subjected to thermal aging treatment at different temperatures of 140 °C and 180 °C respectively and a constant holding time of 12 hours. The research was carried out according to the ASTM G32-2016 norms, on a vibrating device with piezoceramic crystals from the Cavitation Laboratory of the Polytechnic University of Timisoara. The research results, based on characteristic curves, mechanical properties, micro and macro structural images, showed that the sample kept for 12 h at a temperature of 180 °C is weaker than the control sample, during the sample time kept for 12 h at a temperature of 140 °C, has a small increase, even if, compared to the control sample (without heat treatment), the hardness is lower.

Abstract: The use of aluminum alloys in the manufacture of hydropneumatic systems components is very known. However, the knowledge of their behavior under cavitational demands, determinated of flow of the working liquid, is limited. For this reason, in recent years, the older research, carried out on this type of material and on some of its alloys, regarding the resistance to cavity erosion, has been resumed, especially since the mechanical properties and reduced mass are an advantage for the parts that work in this conditions (ship propellers, pumps and bodies of hydraulic devices, etc.). Therefore, the results of this paper are in step with the new researches, highlighting the behavior and resistance to the erosion produced by vibrating cavitation on the aluminum alloy 6082 subjected to the thermal aging treatment at 140 °C, with a holding time of 12 hours. The performance evaluation is based on the characteristic curves of the cavity, the specific parameters and the macro and microstructural investigations. The comparison with the delivered state shows a double increase in resistance from the cavitational erosion created by the shock waves and microjets.