Processability of high-strength aluminum 6182 series alloy via laser powder bed fusion (LPBF)

The growing demand for more materials available for the LPBF-process, in particular high-strength aluminum alloys, is evident in the market. In the present work, a systematic investigation of the processability of aluminum 6182 series alloys, using LPBF, was carried out. For this purpose, the influence of process parameters, especially of enhanced preheating by heating the substrate plate during the LPBF process, on the microstructure of EN AW 6182 specimens was studied.Experiments were conducted at different preheating temperatures always using the same d-optimal design-of-experiments, the laser power, scanning speed, hatch distance, and laser focus position being varied over a wide range.It was found that the preheating temperature has the strongest impact on hot cracking. Higher temperatures result in a significantly reduced number of hot cracks in the microstructure. Moreover, an equiaxed microstructure of the specimens manufactured can be observed at preheating temperatures of 500 °C. In addition to the preheating temperature, the achievable part density is most strongly affected by the laser focus position and the laser power, whereas the hatch distance shows no discernible impact on the part density. Furthermore, neither the hatch distance nor the laser focus position shows any significant effect on hot cracking.In combination with the optimal scanning parameters, crack-free parts with a fully equiaxed grain structure and densities > 99.0% can be manufactured via LPBF at a preheating temperature of 500 °C.

Microstructural and Process Parameters of aluminium alloys Using FSW

Friction stir welding (FSW) has become a popular method for connecting low weight metals. Material joining occurs in the solid state in FSW. Inserting a rotating tool travelling over the faying surfaces of the material to be bonded is used to complete the procedure. It produces practically defect-free welds with little distortion and a fine grain structure. However, the welding mechanism and process parametric combination for welds with consistent and dependable outcomes are not well understood. The thesis details the experimental efforts made to suggest an optimal combination of parameters with simple tool geometry for FSW at greater linear speeds. The materials for research were two precipitation hardenable aluminium alloys: 6mm thick 2219-T87 and 5083H321. The influence of process parameters on weld microstructural changes and defect development was also examined. The optimal combination of process parameters for the FSW of aluminium alloys was proposed, and the most relevant parameter for weld strength and quality was discovered.

Effects of drilling parameters on delamination of kenaf-glass fibre reinforced unsaturated polyester composites

Drilling is a secondary material removal and usually carried out to facilitate fastening of parts together. Drilling of composite materials is not usually a problem-free process. Issues related to delamination composite laminates need to be addressed because it introduces the stress concentration point on the composite. This study focussed on the influence of process parameters such as spindle speed, feed rate, type of drill bits and geometry on the extend of delamination experienced by the composite during the drilling process of kenaf-glass fibre-reinforced unsaturated polyester composite, and the delamination measurements were taken under a microscope. Taguchi methods and analysis of variance were employed to find the optimal parameters. From the results, the most significant parameter was the feed rate. The minimum delamination was achieved when the feed rate was 0.05 mm/rev and spindle speed was 700r/min using both types of drill bits. The quality of the drill hole using the twist drill bit has been proven to be better than the brad drill bit.

Adjustment of the scan track spacing and linear input energy to fabricate dense, pseudoelastic Nitinol shape memory alloy parts by selective laser melting

Nitinol is a well-known shape memory alloy (SMA) which is widely used due to its unique properties such as shape memory effect and pseudoelasticity. However, challenges fabricating Nitinol parts have limited the use of this alloy. Nowadays, additive manufacturing methods, specifically selective laser melting (SLM), are being used as an alternative to conventional methods for fabricating Nitinol specimens. Achieving a dense structure and controlling the transformation temperatures in such products have been among the most important challenges for several research groups. In the present study, fabrication of dense Nitinol parts by SLM together with control of their transformation temperatures is investigated with the main purpose of achieving pseudoelastic products at room temperature. For this purpose, the effect of process parameters on density, transformation temperatures, microstructure, hardness, and shape memory response are studied. The influence of process parameters on transformation temperatures varies depending on the amount of power so that the effect of scan tracks spacing for high powers is more pronounced than that for low powers. The hardness and compressive strength of the parts are also affected by the process parameters. Accordingly, optimal parameters are found to fabricate dense pseudoelastic parts with the ability of strain recovery at ambient temperature.

Microstructural, Thermal and Corrosion Characterization of Friction Stir Welded Magnesium Alloys

The requirement for structural materials with demanding properties is always a major concern among automotive researchers. Magnesium alloys possess the required properties. In this work magnesium alloys, AZ31B and AZ91B were joined by friction stir welding. The influence of process parameters on the weld properties has been studied. The process parameters were tool rotational speed, welding speed, tilt angle. Three different combinations AZ31B-AZ91B, AZ31B-AZ31B and AZ91B-AZ91B were friction stir welded. Non-destructive tests have been performed on the welded joints as the primary analysis. After mechanical testing, optical microscopic examination comprising of macrostructure analysis, microstructure analysis and SEM analysis were carried out on selected specimens and the results are formulated. The corrosion behavior of Mg alloys has been tested using a salt spray test. The thermal behavior was studied using thermogravimetric and differential thermal analysis. The joints were friction stir welded with maximum efficiency where grain refinement was observed in the weld microstructure of dissimilar alloys and the elongated grains was recrystallized. This paper primarily focuses on the microstructural aspects, corrosion performances and TG/DTA analysis.

Design and Simulation Study of the Induction Heated Injection Mold with Sliders

In order to increase the quality of the products manufactured by injection molding, RTC technology can be used to achieve higher mold temperatures. As a result, the path of the injected melt can be extended, allowing the production of parts with more complex shapes and greater length. Induction heating allows heating only selected forming surfaces of the mold which increases the speed and efficiency of the process. This paper presents the concept of a detachable inductor integrated with sliders to enable the application of this technology in an injection mold with sliders, along with the theoretical model used to perform the tests. First, the effect of the magnetic concentrator shape on the process was analyzed. This was followed by a simulation study of the influence of process parameters: heating time, frequency, and electric current. An extensive analysis of the test results of the temperature distribution on the insert allowed for the selection of parameter sets that would enable obtaining the desired surface temperature without a major increase in process time. The results of simulation studies confirm the possible applications and present the range of parameters for obtaining the optimal process.

Process and device simulations aimed at improving the emitter region performance of silicon PERC solar cells

Achieved levels of Silicon-based passivated emitter and rear cell (PERC) solar cells' laboratory and module-level conversion efficiencies are still far from the theoretically achievable Auger limit of 29.4% for silicon solar cells, prominently due to emitter recombination and resistive losses. The emitter region in PERC devices is formed by using either ion implantation followed by a diffusion process or POCl3 diffusion. In ion-implanted emitter-based PERC, the process variables such as dose, energy, diffusion time, and temperature play a vital role in defining the characteristics of the emitter region. Detailed investigation of these parameters could provide a pathway to mitigate the recombination as well as resistive losses; however, it requires a considerable budget to optimize these parameters through a purely experimental approach. Therefore, advanced industrial standard process and device simulation are perceived in this work to carry out the comprehensive study of process variables. Investigation of ion implantation and diffusion process parameters on the PV performance of an upright pyramid textured, industrial standard stacked dielectric passivated PERC solar cell is carried out to deliver 22.8% conversion efficiency with improved PV parameters such as short circuit current density (JSC) of 40.8 mA/cm2, open-circuit voltage (VOC) of 686 mV, and fill-factor (FF) of 81.54% at optimized implantation and diffusion parameters, such as implantation dose of 5×1015 cm-2 with energy 30 keV followed 950 oC diffusion temperature and 30 min of diffusion time. The performance of the optimized PERC device is compared with already published large area screen printed contact-based device. This work may open up a window for the experimental work to understand the influence of process parameters on the emitter region to develop the highly efficient PERC solar cell in the future.

Studies on the influence of process parameters on the protection performance of the outer layer of fire-protective clothing

During an operation, the turnout gear for firefighters must meet two important requirements: thermal protection and comfort. As comfort and protection are inherently incompatible, it is impossible to satisfy both. As part of this study, the outer layer of multilayered turnout suits was analyzed under the influence of various factors such as intensity of heat flux, pick density, and air space between the fabric and the sensor. Choosing Nomex IIIA was based on its inherent properties that are conductive to thermal protection. To simulate the environment encountered during firefighting, benchtop experiments were designed. A system equation for the prediction of the protection time (t-protection) was developed based on a three-factor and three-level Box–Behnken model. The predicted values of t-protection obtained for all the experimental blocks in the design space were subjected to ANOVA analysis which showed that the system equation, as well as the coefficients of linear interactive and square terms, is significant, so the system equation can be efficiently used for predicting t-protection. The validity of the system equation was verified by using the same experimental blocks and estimating t-protection using the Stoll criteria. The accuracy of the system equation was checked by comparing t-protection and t*-protection which revealed a linear relationship with a high correlation coefficient (R2 = 0.975). To analyze the effects of the independent variables on protection time, 3D surface response curves were created. The nature of the surfaces was critically analyzed by developing regression equations for the contours and the diagonals.