Varying Process Parameters Research Articles

Validation of an experimentally-based heat source for flash heating modeling of directed energy deposition: Systematic study of process and simulation parameters

Computational prediction of the temperature history during directed energy deposition (DED) is a fundamental input for the subsequent numerical analysis of microstructural characteristics and thermomechanical response. In order to allow for industrial implementation of such simulations, the development of computationally efficient methods taking advantage of multi-scaling techniques is needed. This work provides a new formulation for the flash heating (FH) method to be applied when modeling DED. As with other FH methods, this formulation ensures energy conservation when defining the volumetric heat source term, however, in the present case, the actual deposited cross-sectional area obtained from experiments is used instead of hatch spacing and layer thickness as usually done in FH methods for laser powder bed fusion (LPBF). A new feature of the model is that the high-resolution cross-sectional area of the multi-layer geometry is extracted from optical micrographs, resulting in a curvilinear top surface of every track. The method is validated through comparison with experimental monitoring data and provides valuable information regarding cooling rates, development of the molten area, and heat accumulation when varying process parameters within relevant limits. The influence of varying simulation parameters, such as the partitioning of the geometry and the time used for heating (contact time), on computational cost and accuracy is moreover studied. It is found that a very short contact time is mandatory to ensure the melting of the geometry and, consequently, the proper evaluation of cooling rates and thermal gradients.

Development of an indirect measurement method for the Contact Tube to Workpiece Distance (CTDW) in the Direct Energy Deposition – Arc (DED-ARC) process for different arc types

During the layer-by-layer build-up in the Direct Energy Deposition (DED) - Arc additive manufacturing (AM) process, the distance between the contact tube and the workpiece, effectively the welded layer, changes. Since the weld paths are predefined by the path planning software, a constant Contact Tube to Workpiece Distance (CTWD) and weld bead height is assumed. However, even small changes in geometry, such as crossovers of weld paths, result in higher weld beads than assumed. Similarly, an incorrectly assumed bead height as input to the path planning will result in a change in the CTWD. The sum of the deviations of the real weld geometries from the assumed ones in the path planning can greatly influence the CTWD. This implies that the dimensional accuracy may be significantly compromised. This research presents an approach for a general indirect measurement method using the welding current to obtain the CTWD during the actual welding process. A real-time process control method is implemented and validated using the mechanically controlled short arc and the pulsed arc process. Varying process parameters are used to validate the general applicability for a specific material. For the mechanically controlled short arc process, the model underestimates the measured CTWD by a mean error of 3.4 mm. The pulse process is overestimated by a mean error of 2.2 mm. The standard deviation for the pulse process with 1.3 mm is slightly smaller than for the short arc process with 1.7 mm.

Thickness Variation of Conductive Polymer Coatings on Si Anodes for the Improved Cycling Stability in Full Pouch Cells.

Si-dominant anodes for Li-ion batteries provide very high gravimetric and volumetric capacity but suffer from low cycling stability due to an unstable solid electrolyte interphase (SEI). In this work, we improved the cycling performance of Si/NCM pouch cells by coating the Si anodes with the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) prior to cell assembly via an electropolymerization process. The thicknesses of the PEDOT coatings could be adjusted by a facile process parameter variation. Glow-discharge optical emission spectroscopy was used to determine the coating thicknesses on the electrodes prior to the cell assembly. During electrochemical testing, improvements were observed closely linked to the PEDOT coating thickness. Specifically, thinner PEDOT coatings exhibited a higher capacity retention and lower internal resistance in the corresponding pouch cells. For the thinnest coatings, the cell lifetime was 18% higher compared to that of uncoated Si anodes. Postmortem analyses via X-ray photoelectron spectroscopy and cross-sectional scanning electron microscopy revealed a better-maintained microstructure and a chemically different SEI for the PEDOT-coated anodes.

Crystallographic Texture Evolution in 3D Printed Polyethylene Reactor Blends.

In this work, crystallographic texture evolution in 3D printed trimodal polyethylene (PE) blends and high-density PE (HDPE) benchmark material were investigated to quantify the resulting material anisotropy, and the results were compared to materials made from conventional injection molded (IM) samples. Trimodal PE reactor blends consisting of HDPE, ultrahigh molecular weight PE (UHMWPE), and HDPE_wax have been used for 3D printing and injection molding. Changes in the preferred orientation and distribution of crystallites, i.e., texture evolution, were quantified utilizing the wide angle X-ray diffraction through pole figures and orientation distribution functions (ODFs) for 3D printed and IM samples. Since the change in weight-average molecular weight (Mw) of the blend was expected to significantly affect the resulting crystallinity and orientation, the overall Mw of the trimodal PE blend was varied while keeping the UHMWPE component weight fraction to 10% in the blend. The resulting texture was analyzed by varying the overall Mw of the trimodal blend and the process parameters in 3D printing and compared to the texture of conventional IM samples. The printing speed and orientation (defined with respect to the axis along the length of the samples) were used as the variable process parameters for 3D printing. The degree of anisotropy increases with an increase in the nonuniform distribution of intensities in pole figures and ODFs. All the highest intensity major texture components in IM and 3D printed samples (0° printing orientation) of reactor blends are observed to have crystals oriented in [001] or [001̅]. Overall, for the same throughput, 3D printed samples in the 0° orientation showed greater texture evolution and higher anisotropy compared to IM samples. Most notably, an increase in 3D printing speed increased the crystalline distribution closer to the 0° direction, increasing the anisotropy, while deviation from this printing orientation reduced crystalline distribution closer to the 0° direction, thus increasing isotropy. This demonstrates that tailoring material properties in specific directions can be achieved more effectively with 3D printing than with the injection molding process. Change in the overall Mw of the trimodal PE blend changed the preferential orientation distribution of the crystal planes to some degree. However, the degree of anisotropy remained the same in almost all cases, indicating that the effect of molecular weight distribution is not as significant as the printing speed and printing orientation in tailoring the resulting properties. The 3D printing process parameters (speed and orientation) were shown to have more influence on the texture than the material parameters associated with the blend.

Optimizing FDM process parameters: predictive insights through taguchi, regression, and neural networks

Fused deposition modelling (FDM) is a popular additive manufacturing process used for rapid prototyping and the production of complex geometries. Despite its popularity, FDM’s susceptibility to variations in numerous process parameters can significantly impact the quality, design, functionality, and mechanical properties of 3D printed parts. This study explores thirteen FDM process parameters and their influence on the mechanical properties of polylactic acid (PLA) polymer, encompassing surface roughness, warpage, tensile and bending strength, elongation at break, deformation, and microhardness. The optimum parameters were identified alongside key contributors by applying the Taguchi method, signal-to-noise ratios, and analysis of variances (ANOVA). Notably, specific FDM parameters significantly affect the surface profile, with layer thickness contributing 32.65% and fan speed contributing 8.59% to the observed variations. Similarly, warping values show notable influence from nozzle temperature (29.53%), wall thickness (16.74%), layer thickness (16.56%), and retraction distance (12.80%). Tensile strength is primarily determined by wall thickness (31.83%), followed by infill percentage (26.73%) and infill pattern (16.18%). Elongation at break predominantly correlates with wall thickness (44.82%), with a supplementary contribution from nozzle temperature (10.90%). Microhardness lacks a dominant parameter. Bending strength variations primarily arise from layer thickness (38%), wall thickness (37.6%), and infill percentage (9.17%). Deformation tendencies are influenced by layer thickness (19.20%), print speed (11.37%), wall thickness, and fan speed (10.9% each). The optimized dataset of FDM process parameters was then employed in two prediction models: multiple-regression and artificial neural network (ANN). Evaluation based on the correlation coefficient (R2) and root mean squared error (RMSE) indicates that the ANN model outperforms the multiple-regression approach. The results indicate that precise control of FDM parameters, coupled with ANN predictions, facilitates the fabrication of 3D printed parts with the desired mechanical characteristics.

Implementation of mechanistic modeling and global sensitivity analysis (GSA) for design, optimization, and scale-up of a roller compaction process

The pharmaceutical industry has been shifting towards the application of mechanistic modeling to improve process robustness, enable scale-up, and reduce time to market. Modeling approaches have been well-developed for processes such as roller compaction, a continuous dry granulation process. Several mechanistic models/approaches have been documented with limited application to high drug-loaded formulations. In this study, the Johanson model was employed to optimize roller compaction processing and guide its scale-up for a high drug loaded formulation. The model was calibrated using a pilot-scale Minipactor and was validated for a commercial-scale Macropactor. Global sensitivity analysis (GSA) was implemented to determine the impact of process parameter variations (roll force, gap, speed) on a quality attribute [solid fraction (SF)]. The throughput method, which estimates SF values of ribbons using granule production rate, was also studied. The model predicted SF values for all 14 Macropactor batches within ± 0.04 SF. The throughput method estimated SF with ± 0.06 SF for 7 out of 11 batches. GSA confirmed that roll force had the largest impact on SF. This case study represents a process modeling approach to build quality into the products/processes and expands the use of mechanistic modeling during drug product development.

Properties of silicon dioxide coatings obtained by nano physical vapor deposition (PVD) method on the titanium 13‐niobium 13‐zirconium alloy

AbstractSurface modification techniques play an important role in adjusting the physicochemical properties of titanium and its alloys. To reduce the penetration of alloying element ions into the body, various types of oxide coatings are used to protect it from the corrosive environment. Another important issue related to the surface layer requirement is ensuring an appropriate set of mechanical properties. Accordingly, in this study, the mechanical and electrochemical properties of the silicon dioxide layers formed by the deposition of nano physical vapor deposition on the surface of titanium and titanium 13‐niobium 13‐zirconium alloy samples were investigated. To evaluate the mechanical properties of the layers produced by this method, hardness tests were carried out, as well as tests on the adhesion of these layers to the metal substrate. On the other hand, electrochemical properties were studied using potentiodynamic measurements to assess the resistance to pitting corrosion, followed by impedance measurements to interpret the processes and phenomena occurring at the silicon dioxide layer/electrolyte interface. The data obtained showed different mechanical and electrochemical properties of the silicon dioxide layers generated with varying process parameters.

Development of a new laboratory-scale reduction facility for the hydrogen plasma smelting reduction of iron ore based on a multi-electrode arc furnace concept

Steel production accounts for a significant share of industrial CO2 emissions. The HPSR process is a possible alternative to reduce these emissions massively if not completely negate them. In principle, Fe-ore is reduced at high temperatures in the plasma of a DC electric arc. hydrogen reacts with the oxidic melt at the gas-liquid interface. Various concepts for the hydrogen plasma reduction of iron ore have been investigated, but the process technology has not yet surpassed the demonstration scale (TRL5). Experimental setups for charging masses from a few grams to a few hundred kilograms have been realized. Further investigations on the process stability and the reaction kinetics are still necessary. An improved laboratory-scale furnace concept shall provide the basis for the fundamental research. An existing laboratory facility is the starting point for designing and constructing the new plasma furnace. There are several problems with this experimental setup. Mainly, the reactor’s dimensions and power supply limitations restrict the arc’s length. The first leads to problems with excessive refractory wear, while the latter limits the variation of process parameters. Strong cooling when using Fe crucibles and the unstable nature of the arc complicate the process control. A promising concept to deal with the problem of arc stability is the use of multiple electrodes in a direct current arc furnace. Together with an optimized furnace geometry, new potential for further investigations can open. Using a multi-cathode furnace is also promising to further explore ferroalloy production via hydrogen plasma reduction. An electric arc furnace was designed based on the requirements for the planned plasma reduction facility. The energy requirement was based on assumptions for heat transfer from the arc to the melt, walls, and lid and continuous transfer through the individual furnace parts. Considerations of power supply, hearth dimensions, refractory design, controlled gas atmosphere, and the implementation of auxiliary equipment were central to creating an ideal basis for various experimental setups.

Encapsulation of Fennel Essential Oil in Calcium Alginate Microbeads via Electrostatic Extrusion

Fennel essential oil (EO) is well known for its biological activities and wide potential for use in the food, cosmetic, and pharmaceutical industries, where the main challenge is to achieve higher stability of EO. This study aimed to evaluate the potential of electrostatic extrusion for encapsulation of fennel EO by examining the effects of alginate (1%, 1.5%, and 2%) and whey protein (0%, 0.75%, and 1.5%) concentrations and drying methods on the encapsulation efficiency, loading capacity, bead characteristics, and swelling behavior of the produced fennel EO microbeads. Results revealed that electrostatic extrusion proved to be effective for encapsulating fennel EO, with whey protein addition enhancing the examined characteristics of the obtained microbeads. Freeze-drying exhibited superior performance compared to air-drying. Optimal encapsulation efficiency (51.95%) and loading capacity (78.28%) were achieved by using 1.5% alginate and 0.75% whey protein, followed by freeze-drying. GC-MS analysis revealed no differences in the qualitative aspect of the encapsulated and initial EO, with the encapsulated EO retaining 58.95% of volatile compounds. This study highlighted the potential of electrostatic extrusion using alginate and whey protein as a promising technique for fennel EO encapsulation while also emphasizing the need for further exploration into varied carrier materials and process parameters to optimize the encapsulation process and enhance product quality.

Temperature evolution, IMC formation, and resulting bonding efficacy in bimetallic tubular components fabricated by a novel friction stir backward extrusion cladding method

The ability to economically offer distinct properties within a single component has gathered significant attention for bimetallic or cladded tubular components across various industries. A novel friction stir-based cladding method and its in-depth analyses to achieve internal cladding of Al inside the stainless steel (SS) tubes are presented. The process outcome with the variation in process parameters and its impact on heat generation and intermetallic compounds (IMCs) formation was analyzed. In this process, the joining between the base substrate and the cladded material is due to the heat generation that leads to interdiffusion and ultimately promotes the formation of IMCs. The mechanism of IMCs formation, its growth phenomenon, and its impact on joining efficacy were investigated. The cladded Al exhibited an approximately twofold increase in grain size compared to the base Al alloy, as revealed through electron back-scattered diffraction (EBSD) analysis. The coarser grains help to restrict the propagation of fracture during the flattening test. The cladded tube exhibits no sign of delamination after compression, which paves the way for the industrial adoption of the process.

Deep-reactive ion etching of silicon nanowire arrays at cryogenic temperatures

The pursuit of sculpting materials at increasingly smaller and deeper scales remains a persistent subject in the field of micro- and nanofabrication. Anisotropic deep-reactive ion etching of silicon at cryogenic temperatures (cryo-DRIE) was investigated for fabricating arrays of vertically aligned Si nanowires (NWs) of a large range of dimensions from micrometers down to 30 nm in diameter, combined with commonly used wafer-scale lithography techniques based on optical, electron-beam, nanoimprint, and nanosphere/colloidal masking. Large selectivity of ∼100 to 120 and almost 700 was found with resists and chromium hard masks, respectively. This remarkable selectivity enables the successful transfer of patterned geometries while preserving spatial resolution to a significant extent. Depending on the requirements by applications, various shapes, profiles, and aspect ratios were achieved by varying process parameters synchronously or asynchronously. High aspect ratios of up to 100 comparable to the best result by metal-assisted wet-chemical etching and sub-μm trenches by DRIE were obtained with NW diameter of 200 nm, at an etch rate of ∼4 μm/min without being collapsed. At the same time, low surface roughness values were maintained on the NW top, sidewall, and bottom surface of ∼0.3, ∼13, and ∼2 nm, respectively, as well as high pattern fidelity and integrity, which were measured using angle-resolved Fourier microscopy, combined atomic force, and scanning electron microscopy on selected NWs. This work establishes the foundation in the controllable development of Si nanoarchitectures, especially at sub-100 nm structures, for energy-harvesting and storage, damage-free optoelectronics, quantum, photovoltaics, and biomedical devices.

Tailoring surface roughness through the temporal variation of additive manufacturing process parameters

The benefits that additive manufacturing (AM) offers to the industry are generally well understood and appreciated. However, the current design for additive manufacturing (DfAM) methodologies and computer-aided manufacturing (CAM) packages neglect to exploit the full potential that AM can offer through its unique ability to vary material characteristics whilst the final component geometry is being formed. The purpose of this research is to demonstrate that additional design control can be gained through temporal DfAM (TDfAM). In this study, the ability to tailor the surface roughness of fused deposition modelling (FDM) AM polylactic acid (PLA) parts through the variation of two process parameters, nozzle temperature and print speed, is explored. The underpinning hypothesis is that variation of temperature and printing speed, can provide a significant change of surface roughness within one homogeneous part. This research demonstrated that nozzle temperature and print speed have a statistically significant effect on the surface roughness of the top and side surfaces. By increasing temperature and speed, the roughness of the side surfaces decreased and the roughness of the top surface increased. Furthermore, the in-silico implementation of TDfAM is demonstrated. As such, the research supports the hypothesis that TDfAM can enable additional control over the surface characteristics of a homogeneous part.

The effect of the laser beam intensity profile in laser-based directed energy deposition: A high-fidelity thermal-fluid modeling approach

Modeling the thermal and fluid flow fields in laser-based directed energy deposition (DED-LB) is crucial for understanding process behavior and ensuring part quality. However, existing models often fail to accurately predict these fields due to simplifying assumptions, particularly regarding powder particle-induced attenuation in laser power and energy density distribution, and the variable material properties and process parameters. The present work introduces a high-fidelity multi-phase thermal-fluid model driven by a combination of the discrete element method (DEM) and the finite volume method (FVM). Incorporating an enhanced attenuation model for laser energy enables a more precise approximation of powder particle-induced attenuation effects in the laser power and energy density distribution. The study focuses on the influence of laser beam intensity profiles during DED-LB of austenitic stainless steel (AISI 316 L), with model validation conducted through experimental measurements of deposited track dimensions for different beam shapes. The results of numerical simulations demonstrate the critical impact of powder-induced attenuation on the laser power and intensity profiles. Neglecting laser energy attenuation, a common assumption in numerical simulations of DED-LB, leads to overestimations of the absorbed energy of the laser beam, affecting thermal and fluid flow fields, and melt pool dimensions. The present study unravels the complex relationship between the attenuation coefficient (due to the powder stream) and powder stream characteristics, describing the variations of the attenuation coefficient with changes in the powder mass flow rate and powder stream incidence angle. The findings show the critical effects of laser beam shaping on melt pool behavior in DED-LB, with square beams inducing larger melt pool volumes and circular beams creating smaller but deeper melt pools. The proposed enhanced thermal-fluid modeling framework offers a robust approach for optimizing laser-based additive manufacturing across diverse materials and laser systems.

Effects of processing parameters on the leakage current of silicone rubber insulator

Silicone rubber (SiR) is known for its exceptional electrical insulation properties. The performance of SiR could be affected by many factors, including processing parameters, particularly mixing speed and time. While these parameters are crucial for ensuring the homogeneity of blended polymeric materials, their electrical impact remains relatively unexplored. This research investigates the effect of varying processing parameters on SiR samples during rapid aging under the incline plane tracking (IPT) test. The study unfolds in three phases, with the final IPT stage revealing the significant influence of different mixing speeds and times on the recorded leakage current (LC) values for each sample. Sample 2, subjected to 70 rpm mixing speed and 10 minutes of mixing time, exhibited great resistance to tracking and erosion. Fourier transform infrared spectroscopy (FTIR) was conducted on the samples before and after the IPT test to further analyze the impact of the varying processing parameters. Once again, sample 2 displayed notable resilience, demonstrating lower reductions in absorbance values for key functional groups. In conclusion, the specific processing parameters of 70 rpm and 10 minutes have been shown to positively influence the performance of SiR, enhancing their resistance to tracking and erosion during rapid aging.

Ultrasonic fortification of interfiber autohesive contacts in meltblown nonwoven materials

Autohesion is a unique class of adhesion that enables the bonding of two identical surfaces by establishing intimate contact at interfaces. Creating intimacy between two identical surfaces poses a challenging task, often constrained by the presence of surface roughness and chemical heterogeneity. To surmount this challenge, we document a variety of autohesive traits in polypropylene-based meltblown nonwovens, accomplished through a facile, scalable, energy-efficient, and cost-effective ultrasonic bonding process. The mean work of autohesion for a single polypropylene bond, serving as a figure of merit, has been computed by extending the classical Johnson−Kendall−Roberts (JKR) theory by factoring in peel strength along with key fiber and structural parameters of nonwoven materials. Achieving a high figure of merit in ultrasonically bonded nonwovens hinges on the synergistic interplay of key process parameters, including static force, power, and welding speed, with the fiber and structural properties acting in concert. In this regard, peel-off force analysis has also been conducted on a series of twenty-seven ultrasonically bonded meltblown nonwovens prepared using a 33 full factorial design by systematically varying process parameters (static force, power, and welding speed) across three levels and extension rate. X-ray microcomputed tomography (microCT) analysis has been performed on select ultrasonically bonded nonwoven samples to discern their bulk characteristics. A broad spectrum of mean work of autohesion for a single polypropylene bond, ranging from 1.88 to 9.93 J/m², has been ascertained by modulating key process parameters.

Modeling-based Approach Towards Quality by Design for a Telescoped Process.

A telescoped, two-step synthesis was investigated by applying Quality by Design principles. A kinetic model consisting of 12 individual reactions was successfully established to describe the synthesis and side reactions. The resulting model predicts the effects of changes in process parameters on total yield and quality. Contour plots were created by varying process parameters and displaying the model predicted process response. The areas in which the process response fulfils predetermined quality requirements are called design spaces. New ranges for process parameters were explored within these design spaces. New conditions were found that increased the robustness of the process and allowed for a considerable reduction of the used amounts of a reagent. Further optimizations, based on the newly generated knowledge, are expected. Improvements can either be direct process improvements or enhancements to control strategies. The developed strategies can also be applied to other processes, enhancing upcoming and preexisting research and development efforts.

Industrial implementation of a next generation advanced high strength steel

This study describes a suitable process for manufacture of a cold rolled and continuous annealed advanced high strength steel with a carbide-free bainitic ferrite or quenching and partitioning microstructure in an existing annealing production line. The effect of variations of the main processing parameters on the phase transformation responses and mechanical properties of potential candidate steels was investigated with particular focus on the effect of the overaging temperatures. The relationship between the microstructure and the tensile properties and the hole expansion capacity was scrutinized. In addition to the second phases such as fresh martensite and retained austenite, the non-relaxed strain gradient in the microstructures might be an important parameter to influence the hole expansion capacity.

High-frequency characteristics of multilayer graphene nanoribbon interconnects: Exploring the implications OF SKIN effect

A study is undertaken to explore the frequency-dependent traits of crosstalk delay (X-D), crosstalk noise area (X-NA), and the mean time to failure induced by electromigration (EM-MTF) in interconnects constructed from lithium-doped multilayer graphene nanoribbon (Li-MLGNR) and their optimized counterparts, known as optimized Li-MLGNR (O-LiMLGNR) interconnects. The analysis is based on the skin depth and impedance model incorporating scatterers and the finite thickness of the interconnect. The obtained high-frequency impedance and performance characteristics reveals that O-LiMLGNR outperforms Li-MLGNR, rough copper, and mixed carbon nanotube bundle in terms of X-D, X-NA, and EM-MTF. Subsequently, the performance of O-LiMLGNR, limited by process and temperature variations, is analyzed at high frequencies under the influence of skin-effect. As a result of variations in process parameters and temperature, the O-LiMLGNR exhibits an increase in variations of X-D and X-NA, accompanied by a reduction in variation of EM-MTF as the frequency increases.

Enhancing Manufacturability of SU-8 Piezoelectric Composite Films for Microsystem Applications.

Piezoelectric thin films are extensively used as sensing or actuating layers in various micro-electromechanical systems (MEMS) applications. However, most piezoelectrics are stiff ceramics, and current polymer piezoelectrics are not compatible with microfabrication due to their low Curie Temperature. Recent polymer-composite piezoelectrics have gained interest but can be difficult to pattern. Photodefinable piezoelectric films could resolve these challenges by reducing the manufacturability steps by eliminating the etching process. But they typically have poor resolution and thickness properties. This study explores methods of enhancing the manufacturability of piezoelectric composite films by optimizing the process parameters and synthesis of SU-8 piezo-composite materials. Piezoelectric ceramic powders (barium titanate (BTO) and lead zirconate titanate (PZT)) were integrated into SU-8, a negative epoxy-based photoresist, to produce high-resolution composites in a non-cleanroom environment. I-line (365 nm) light was used to enhance resolution compared to broadband lithography. Two variations of SU-8 were prepared by thinning down SU-8 3050 and SU-8 3005. Different weight percentages of the piezoelectric powders were investigated: 5, 10, 15 and 20 wt.% along with varied photolithography processing parameters. The composites' transmittance properties were characterized using UV-Vis spectroscopy and the films' crystallinity was determined using X-ray diffraction (XRD). The 0-3 SU-8/piezo composites demonstrated resolutions < 2 μm while maintaining bulk piezoelectric coefficients d33 > 5 pm V-1. The films were developed with thicknesses >10 μm. Stacked layers were achieved and demonstrated significantly higher d33 properties.

Effect of processing parameters on the microstructure, mechanical properties and thermal expansion behavior of Invar 36 alloy manufactured by laser powder bed fusion

Invar 36 alloy manufactured via the laser powder bed fusion (LPBF) process have attracted interest for their excellent low expansion properties. The properties of Invar 36 alloy, particularly thermal expansion, are highly sensitive to variations in process parameters. However, the effect of process parameters on microstructure and properties has not been systematically studied. This study examines the microstructure, mechanical properties, and coefficient of thermal expansion (CTE) of Invar 36 alloy under various processing parameters with different volumetric energy densities (VED). The results demonstrate that VED variations significantly impact the microstructure, mechanical properties, and CTE. Increasing VED leads to larger grain size and higher high angle grain boundaries, while geometric dislocation density and Taylor factor do not exhibit a linear relationship. At 89.29 J/mm3 VED, the Invar 36 alloy displays the optimal yield strength (405.4 MPa), tensile strength (489.3 MPa), and elongation (43.3%). The CTE meets the ASTM F1684 standard for all specimens. Lower relative density corresponds to smaller CTE, with the lowest CTE achieved at VED of 41.67 J/mm3. Furthermore, the influence of porosity on CTE diminishes with rising temperature. This research opens up the possibility of process parameters optimization for improved CTE and mechanical properties in as-printed Invar parts.