Conventional Casting Technique Research Articles

Simultaneously enhanced strength-ductility of AlCoCrFeNi2.1 eutectic high-entropy alloy via additive manufacturing

The negative effects of thermal cycles in the process of additive manufacture present a challenge for the control of microstructure so as to fabricate the products with improved properties compared with conventional casting technique. In this work, AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) was prepared by laser metal deposition (LMD). Compared with conventionally cast EHEA samples, the LMD-fabricated EHEA samples showed significantly enhanced tensile strength (by 19.7%) and increased tensile ductility (by 56.4%). Such enhancement in tensile properties was attributed to the refinement of the uniformly distributed eutectic-structure, which improved the strain hardening/dislocation accumulation capability of the EHEA. The present work provides a new strategy to utilize both the high cooling rates of LMD and the eutectic-structure characteristics for forming refined homogeneous structures and thus achieving superior mechanical properties to those prepared by traditional processing techniques.

Comparison of Mechanical and Microstructural Properties of as-Cast Al-Cu-Mg-Ag Alloys: Room Temperature vs. High Temperature

Unfolding the structure–property linkages between the mechanical performance and microstructural characteristics could be an attractive pathway to develop new single- and polycrystalline Al-based alloys to achieve ambitious high strength and fuel economy goals. A lot of polycrystalline as-cast Al-Cu-Mg-Ag alloy systems fabricated by conventional casting techniques have been reported to date. However, no one has reported a comparison of mechanical and microstructural properties that simultaneously incorporates the effects of both alloy chemistry and mechanical testing environments for the as-cast Al-Cu-Mg-Ag alloy systems. This preliminary prospective paper presents the examined experimental results of two alloys (denoted Alloy 1 and Alloy 2), with constant Cu content of ~3 wt.%, Cu/Mg ratios of 12.60 and 6.30, and a constant Ag of 0.65 wt.%, and correlates the synergistic comparison of mechanical properties at room and elevated temperatures. According to experimental results, the effect of the precipitation state and the mechanical properties showed strong dependence on the composition and testing environments for peak-aged, heat-treated specimens. In the room-temperature mechanical testing scenario, the higher Cu/Mg ratio alloy with Mg content of 0.23 wt.% (Alloy 1) possessed higher ultimate tensile strength when compared to the low Cu/Mg ratio with Mg content of 0.47 wt.% (Alloy 2). From phase constitution analysis, it is inferred that the increase in strength for Alloy 1 under room-temperature tensile testing is mainly ascribable to the small grain size and fine and uniform distribution of θ precipitates, which provided a barrier to slip by deaccelerating the dislocation movement in the room-temperature environment. Meanwhile, Alloy 2 showed significantly less degradation of mechanical strength under high-temperature tensile testing. Indeed, in most cases, low Cu/Mg ratios had a strong influence on the copious precipitation of thermally stable omega phase, which is known to be a major strengthening phase at elevated temperatures in the Al-Cu-Mg-Ag alloying system. Consequently, it is rationally suggested that in the high-temperature testing scenario, the improvement in mechanical and/or thermal stability in the case of the Alloy 2 specimen was mainly due to its compositional design.

The Digitalisation in Cobalt-Chromium Framework Fabrication. Surface Roughness Analysis: A Pilot Study

Selective laser melting (SLM) is a new technique in fabricating cobalt-chromium denture framework. However, the surface properties of cobalt-chromium denture framework fabricated using the aforementioned technique have not been widely investigated. The aim of this paper was to investigate the surface roughness of cobalt-chromium alloy in removable partial denture fabricated with SLM technique. Cobalt-chromium denture frameworks were fabricated with two techniques (n = 10); the conventional lost-wax casting (conventional group) and SLM techniques (SLM group). Specimens from the conventional group were subjected to the standard cobalt-chromium denture polishing protocols. No treatment was employed for specimens from the SLM group. All specimens were subjected to surface roughness measurement on polished and fitting surfaces using non-contact optical three-dimensional metrology and surface roughness analysis machine (Infinite Focus Real 3D Alicona). Statistical analysis showed no significant difference in surface roughness between the specimens from conventional and SLM groups (p > 0.05). There was no statistically significant difference in surface roughness between the polished and fitting surfaces of SLM specimens (p > 0.05). Surface roughness quality of the cobalt-chromium denture framework fabricated with the SLM technique is comparable to that fabricated with the conventional lost-wax casting technique. The surface roughness of SLM fabricated cobalt-chromium denture frameworks carries the same surface roughness quality between the polished and fitting surfaces.

Accuracy of a titanium maxillary complete denture baseplate fabricated by using the electron beam melting technique: An in vitro study

Statement of problemElectron beam melting (EBM) is a promising additive manufacturing technique for fabricating denture baseplates; however, studies evaluating its accuracy are sparse. PurposeThe purpose of this in vitro study was to compare the fit accuracy of titanium maxillary complete denture baseplates fabricated by using the EBM technique with those fabricated by using the conventional casting technique and to evaluate the dimensional accuracy of the EBM baseplate by using a 3-dimensional inspection software program. Material and methodsDefinitive casts of an edentulous maxilla were prepared. After the casts were optically scanned, computer-aided designs for the EBM baseplate were created by using a software program for standard tessellation language file editing. The EBM baseplates were fabricated with an EBM machine by using a Grade II titanium powder as the raw material. The cast baseplates were fabricated with a lost-wax casting technique by using refractory casts duplicated from the definitive casts. After fitting the EBM and cast baseplates to their corresponding definitive cast, they were embedded in a Type IV stone. The embedded baseplates on the casts were sectioned at 3 regions: posterior palatal seal, molar, and premolar. The maximum gaps between the baseplate and definitive cast were measured in these 3 regions. The virtual casts obtained by scanning the EBM baseplate were superimposed on the computer-aided design to evaluate the dimensional accuracy. Distribution color maps were then generated, and the mean absolute deviations and root mean square deviations were calculated. One-way analysis of variance and t tests were used for statistical analysis (α=.05). ResultsNo significant differences in the maximum gaps among the 3 regions were found in the cast or EBM baseplate groups (P>.05). The EBM baseplate group showed significantly lower values than the cast baseplate group in all regions (premolar: P=.008; molar: P=.003; posterior palatal seal: P=.004). The mean maximum gap for the 3 regions in the cast baseplates was 168.0 μm and that in the EBM baseplates was 60.7 μm. The distribution color map of the EBM baseplate showed a favorable dimensional accuracy. The mean absolute deviation value was 19.7 μm, and the root mean square deviation value was 25.1 μm. ConclusionsThe EBM baseplates had a significantly higher fit accuracy than the cast baseplates. Thus, the fit accuracy of the EBM technique is suitable for fabricating metal baseplates.

Study the structure of selenium modified polyethylene oxide/polyvinyl alcohol (PEO/PVA) polymer blend

A blend of polyethylene oxide (PEO)/polyvinyl alcohol (PVA) filled with gradient concentrations of selenium nanoparticles (SeNPs) was prepared using a conventional casting technique. The influence of selenium content variation on structural, optical, and surface characteristics of the studied nanocomposite films was evaluated. Characterization studies have shown that the blend ensures a uniform and controlled distribution of SeNPs within the polymer network. Infrared spectral data exhibited changes in the intensities and position of the characteristic absorption peaks within the fingerprint region extended from 1700 to 700 cm −1 for virgin and filled PEO/PVA blend samples. X-ray diffraction pattern of studied nanocomposites displays a semi-crystalline behavior that decreased with increasing SeNPs content. Both FTIR and XRD spectral data support the interaction between organic and inorganic compartments. Furthermore, the UV–visible spectra show a notable increase in absorbance combined with values and a new absorption peak appears at ~200, which gradually shifts to the side of the higher wavelength as the content of SeNPs increases. TEM images confirm the presence of spherical and crystalline SeNPs nanoparticles with radii ranging between 30 and 70 nm.

Enhanced Gas Diffusion in Reversible Solid Oxide Cell Fabricated by Phase-Inversion Tape Casting

Electrochemical characteristics of a hydrogen-electrode-supported solid oxide cell (SOC) fabricated by phase-inversion tape casting are experimentally evaluated in both fuel cell (FC) and electrolysis cell (EC) operations. Particular focus is on the effect of the microchannels formed in the hydrogen electrode on the gas diffusion performance in the electrode. Current-voltage and impedance characteristics are measured and compared with those obtained from an SOC fabricated by conventional tape casting technique. The activation resistance is found to be almost identical between the tested cells because both cells are fabricated with a spin-coated functional layer in the hydrogen electrode. On the other hand, the concentration resistance is significantly decreased in the cell fabricated by the phase-inversion tape casting because the microchannels in the hydrogen electrode enhances the gas diffusion performance. This is more remarkable when the cells are operated in diluted fuel composition and with higher current densities. The asymmetric behavior is observed in the current-voltage characteristics of the cells, meaning that the overpotentials in the FC and EC modes are not the same at the same FC and EC currents. The overpotential is found to be always larger in EC mode, however, the extent of asymmetry is reduced in the cell fabricated by the phase-inversion tape casting. This is mainly because the microchannels in the hydrogen electrode reduces the gas diffusion resistance associated with the steam transport in EC mode. Microstructure of the fabricated cells is also analyzed in micro- and nano-scale to quantify the structure of the microchannels formed in the hydrogen-electrode. The microchannels are initiated below the immersed surface during the phase-inversion process, and then grow towards the bottom of the layer. The average diameter of the microchannels increases, whereas its number density decreases. Also, the total porosity in the phase-inversion electrode is found to be almost the same as that in the conventional cell.

On the microstructure and tensile properties of Inconel 718 alloy fabricated by selective laser melting and conventional casting

In this work, we investigated the microstructure and tensile properties of Inconel 718 alloy processed by selective laser melting (SLM) and conventional casting technique using multiscale characterization methods. Results indicated that a columnar grain structure containing cellular structure units with submicron size was the major feature in the as-printed Inconel 718 alloy. At the cellular structure boundaries, the high-density dislocation tangles, segregation of Nb/Mo atoms and nano-sized Laves phases were found. Meanwhile, we also observed dislocation pile-ups and stacking faults in the interior of the cellular structure. In contrast, in the as-cast Inconel 718 alloy, both the grains and Laves phases were much coarser. Discrete dislocations, dislocation tangles and [Formula: see text]” precipitates were locally observed in the grains. Tensile results showed the as-printed Inconel 718 alloy had a higher strength and a lower elongation in comparison with those in the as-cast alloy. Based on the experimental results, the formation mechanism of the cellular structure was discussed.

Plasticizer effect on dielectric properties of poly(methyl methacrylate)/titanium dioxide composites

The effect of plasticizer on dielectric properties of poly(methyl methacrylate) (PMMA)/titanium dioxide (TiO2) composites was investigated. Propylene carbonate (PC) was used as plasticizer in the samples which were prepared with the conventional solvent casting technique. Scanning Electron Microscopy with Energy Dispersive X-Ray Analysis (SEM-EDX) and Differential scanning calorimetry (DSC) analyses and LCR Meter measurements (performed between 300 K and 400 K), were conducted to examine the properties of the composites. With the addition of plasticizer, the thermal properties have changed and the dielectric constant of the composite has increased significantly. The glass transition temperature of pure PMMA measured 121.7°C and this value did not change significantly with the addition of TiO2, however, 112°C was measured in the sample with the addition 4 ml of PC. While the dielectric constant of pure PMMA was 3.64, the ε′ value increased to 5.66 with the addition of TiO2and reached 12.6 with the addition of 4 ml PC. These changes have been attributed to increase in amorphous ratio that facilitates polymer dipolar and segmental mobility.

Synthesis of Bulk Zr48Cu36Al8Ag8 Metallic Glass by Hot Pressing of Amorphous Powders

The critical cooling rate necessary for glass formation via melt solidification poses inherent constraints on sample size using conventional casting techniques. This drawback can be overcome by pressure-assisted sintering of metallic glass powders at temperatures above the glass transition, where the material shows viscous-flow behavior. Partial crystallization during sintering usually exacerbates the inherent brittleness of metallic glasses and thus needs to be avoided. In order to achieve high density of the bulk specimens while avoiding (or minimizing) crystallization, the optimal combination between low viscosity and long incubation time for crystallization must be identified. Here, by carefully selecting the time–temperature window for powder consolidation, we synthesized highly dense Zr48Cu36Ag8Al8 bulk metallic glass (BMG) with mechanical properties comparable with its cast counterpart. The larger ZrCu-based BMG specimens fabricated in this work could then be post-processed by flash-annealing, offering the possibility to fabricate monolithic metallic glasses and glass–matrix composites with enhanced room-temperature plastic deformation.

Waste Fly Ash Powder Filled Glass Fiber Reinforced Epoxy Composite: Physical, Mechancial, Thermo-mechanical, and Three-body Abrasive Wear Analysis

In the present research work, waste fly ash powder-filled chopped glass fiber reinforced epoxy composites are fabricated. Conventional open mold casting technique is used for fabrication of composite samples. The fly ash powder is incorporated from 0 to 15 wt.% in the composite at an interval of 5 wt.% to analyze the physical (experimental and theoretical densities, void fraction and hardness), mechanical (tensile strength, tensile modulus, flexural strength, flexural modulus, impact strength), thermo-mechanical (dynamic mechanical analysis, DMA), and three-body abrasive wear rate, respectively. From this study, it is clearly seen that density, void fraction, and hardness of the composites improved with fly ash content. The strength and modulus of the composites increased with filler content up to 10 wt.%. For the analysis of the homogeneity of composites, the storage modulus, loss modulus, and the cole-cole plot are drawn from dynamic mechanical analysis. Finally, a three-body abrasive wear test is conducted for composite samples, in a steady-state abrasive wear condition up to 10 wt.% fly ash filled composites shown better wear resistance with the variation in sliding distance and normal load. The Taguchi’s design of experiment method is used for designing of experimental runs having input controlling variables like sliding distance, normal load, filler content, and abrasive size.

Influence of manufacturing technique on marginal fit of cobalt chromium restorations: An in-vitro Study.

For porcelain fused to metal restorations, computer-aided designing (CAD) / computer-aided manufacturing (CAM) systems claim to provide improved marginal fit than conventional casting systems. The present in-vitro study was conducted to compare the marginal fit of cobalt-chromium alloy copings fabricated with milled wax/lost wax, CAD/CAM milling/sintering and direct metal laser sintering (DMLS) techniques. A metal die simulating a prepared tooth was fabricated and scanned using an optical scanner. A standardized coping design was used to manufacture 30 alloy copings divided into three groups of ten copings each i.e., milled wax/lost wax, milling/sintering and DMLS. A modified replica technique was used to measure the silicone film thickness at four pre-designated points on the margin under a digital stereo-microscope. The mean values for marginal gap were compared using one-way Analysis of Variance (ANOVA) followed by Tukey-Kramer test for all pair-wise comparisons. The mean marginal gap values obtained by using milled wax/lost wax technique, milling/sintering technique and DMLS technique were 88.44 μm, 61.135 μm and 55.39 μm, respectively. One-way ANOVA showed a significant difference for marginal fit between the lost wax group and the other two test groups (P < 0.05). The cobalt-chromium alloy copings fabricated using DMLS techniques displayed significantly better marginal fit than the milled wax/lost wax technique which may contribute to their improved clinical performance. DMLS technique produces restorations with an improved marginal fit and may be preferred by clinicians over milling and conventional casting techniques.

Effects of stir casting process parameters on dispersion of reinforcement particles during preparation of metal composites

Abstract The flow behavior of the liquid metal during the stir casting process significantly affects dispersion of reinforcement particles in Metal Matrix Composites (MMCs). Liquid metal processing is carried out in an opaque crucible, in which the flow patterns are invisible. Hence, numerical simulation is an apt tool to understand flow behavior and particle dispersion. Blade angle and stirring speed are two important factors ultimately resulting in the final quality of the composites. Thus, in the present investigation, simulation of stir casting process has been performed to optimize blade angle and stirring speed. In order to compare the results of simulation, MMCs were developed using a conventional stir casting technique. Microscopic investigation and porosity analysis has been incorporated to study dispersion of reinforcement inside molten matrix. Microstructural investigation unveiled the homogeneous distribution of SiC particles in the molten matrix and grain size of composite material is reduced by 10.5% as compared to matrix material.

To Evaluate the Marginal Adaptation of Porcelain Fused to Metal Crown with Different Base Metal Alloys.

Introduction:The success of any restoration depends on the marginal seal. The adaptation of castings, luting cement, and the surface structures of the margins are all important factors in achieving marginal seal.Aim:The aim of this study was to evaluate the vertical marginal discrepancy of cast copings obtained by employing conventional casting technique with two different base metal alloys with two different finish lines before and after porcelain firing.Material and Methods:A total of forty wax copings were fabricated with stainless steel die assembly and divided into four groups with ten specimens for each metal and each finish line. Measurements were recorded from coping margin to the stainless steel die margin for vertical marginal gap recordings. Each metal coping was finished, and porcelain application was completed. Copings with porcelain were placed on their respective dies, again subjected to the same measuring microscope for checking the vertical marginal discrepancy by the same operator and results.Results:The results of the present study showed that the mean vertical marginal gaps of all the cast copings obtained in each group (G1–G8) were within clinically acceptable limits. The mean vertical marginal gap of G1 was 135.36 ± 2.30 μm, G2 was 67.22 ± 4.25 μm, G3: 39.47 ± 2.98 μm, G4: 71.00 ± 3.97 μm, G5: 109.57 ± 2.98 μm, G6: 109.57 ± 2.98 μm, and G8: 114.58 ± 2.40 μm.Conclusion:The difference in the vertical marginal gap of cast copings obtained in different groups was statistically highly significant at 0.005 level, while the difference in the vertical marginal gap of cast copings obtained at different points was statistically nonsignificant.

Environmental and cost assessment of customized modular wall components production based on an adaptive formwork casting mechanism: An experimental study

The application of automation and robotics in construction industry, has shown significant growth in recent decades with examples to include, among others, adaptive casting techniques. Such examples have been few in number and have been assessed, mostly in regard to their qualitative performance. Also, little, fragmented and not fully systematized research has examined their environmental and economic impact, along with the benefits that their application could bring in construction. A comprehensive and systematic investigation of their environmental and economic feasibility based on quantitative results could provide a clearer understanding of their benefits with future goal their widespread use in the construction industry. This hypothesis is tested through an experimental study of an innovative adaptive formwork casting mechanism that is applied for the customized production of a variety of modular brick typologies. The results of implementation and production process are assessed in terms of their life cycle and cost performance, and compared with a conventional casting approach. Adobe, mixture of clay with cement, and concrete, are used as the materials of implementation. The introduction of a novel adaptive formwork casting mechanisms and the results obtained show that the technique can be effectively applied for the construction of modular brick components with large variability. This is due to the advantages that arise in relation to their environmental impact and cost performance in long term, compared to conventional formwork casting techniques. Such applications might open new possibilities in construction industry towards a more sustainable and cleaner casting and production process of customized building components.

EFFECT OF RECASTING CO-CR ALLOYS ON THE MARGINAL FIT OF CROWN WITH SHOULDER MARGIN - AN INVITRO STUDY

Introduction: Marginal adaptation is one of the most important and weakest links in the success of cast restorations. There is some indication that the quality of marginal adaptation may be as important to gingival health as marginal location.01&#x0D; Aims and Objectives: To evaluate the marginal integrity and occlusal discrepancy of base metal alloy copings by recasting method using conventional casting technique.&#x0D; Methodology: The 30 test samples were grouped into 3groups as Group I: 10 samples will be prepared using 100% new co-cr alloy.Group II: 10 samples will be prepared using 50% new alloy and 50% reused alloy.Group III:10 samples will be prepared using 25% new alloy and 75% reused alloy. The patterns obtained were casted with an induction casting machine and Co-Cr copings, the vertical gap and internal gap/occlusal discrepancy of all the 30 Co-Cr cast copings are obtained, with the use of stereo microscope.&#x0D; Results: Paired t test and tukey Kramer tests were conducted to determine p value. The p value for marginal integrity was found to be less than 0.01 which indicates that there is a significant difference between groups on buccal,lingual,mesial and distal surfaces . p value for occlusal discrepancy was found to be greater than 0.01 indicating that there is no significant difference between groups on occlusal mesial surfaces while distal side it is less than 0.01 which is significant.&#x0D; Summary and Conclusion: The patterns were prepared with inlay casting wax on the custom-made stainless steel die. 30 of the patterns were invested with a metal ring during investment. The vertical marginal gaps of three groups cast copings obtained by conventional casting were statistically significant to each other with higher value in group 2 followed by group 3 and group 1.

High Temperature Mechanical and Creep Performance of AA7075/TaC/Si3N4/Ti Hybrid Metal Matrix Composites

An effort was contrived to incorporate aluminium alloy (AA) 7075 reinforced with Silicon Nitride (Si3N4), Tantalum Carbide (TaC), and Titanium (Ti) particulates using conventional stir casting technique. The tension and creep investigations of these composite materials were analysed at room and elevated temperature to regulate their strain to failure and ultimate tensile strength (UTS). The data obtained inferred that addition of these ceramic reinforcements was naturally enhanced the mechanical and creep properties. Strength due to elongation was observed as high as 111.41 N/mm2 at 120°C when compared to unalloyed aluminium alloy. The load tests analysis reveals that the increase in reinforcement wt% of TaC and Ti combinations leads to increase in resistance for deformation failure and the composite is able to with stand 500 kg load at 120°C. The results of the creep tests shows that the ability of the material to with stand an higher cycle time of more than 30,000 seconds when the strain value is 0.02 wt% of reinforcement are 0.5% of TaC, 6% of Si3N4, and 1% of Ti.

Radiographic Assessment of Accuracy of Fit for Different Conical Connection Abutments on Tapered Implants

Purpose: This study aimed to evaluate the accuracy of fit between implant and abutment using different types of abutments. Methods: A total of 32 titanium implants with 3.5mm diameter, 12mm length and conical connection were used in this study. All implants were randomly divided into four equal groups according to the type of the abutment used as follows: Group I (Control Group): Ready-made Titanium abutment . Group II: Custom-made Gold abutment . Group III: Custom-made Co-Cr abutment with prefabricated machined Co-Cr base . Group IV: Custom-made Fully Casted Co-Cr abutment. Abutments for groups II, III, IV were fabricated using the conventional casting technique to obtain custom-made gold abutments for group II and custom-made Co-Cr abutments for groups III, IV. All the abutments were tightened at 35 N/cm using manual Torque Wrench. The x-ray sensor was placed parallel to the implant and a radiograph was taken for each sample. The distance from the end of the base of the abutment till the beginning of the screw holes of the implant was measured in mm. Data were statistically studied. Results: Results showed that Group IV had the statistically significantly highest mean value. Group III showed statistically significantly lower mean value. There was no statistically significant difference between Group I and Group II; both showed statistically significantly lowest mean values. Conclusions: Within the limitations of this study, it was concluded that: Custom-made Co-Cr abutments with prefabricated Co-Cr base revealed promising results. Casted connections don’t seem to be a good alternative to machined connections.

Viscous Flow of Supercooled Liquid in a Zr-Based Bulk Metallic Glass Synthesized by Additive Manufacturing.

The constraint in sample size imposed by the critical cooling rate necessary for glass formation using conventional casting techniques is possibly the most critical limitation for the extensive use of bulk metallic glasses (BMGs) in structural applications. This drawback has been recently overcome by processing glass-forming systems via additive manufacturing, finally enabling the synthesis of BMGs with no size limitation. Although processing by additive manufacturing allows fabricating BMG objects with virtually no shape limitation, thermoplastic forming of additively manufactured BMGs may be necessary for materials optimization. Thermoplastic forming of BMGs is carried out above the glass transition temperature, where these materials behave as highly viscous liquids; the analysis of the viscosity is thus of primary importance. In this work, the temperature dependence of viscosity of the Zr52.5Cu17.9Ni14.6Al10Ti5 metallic glass fabricated by casting and laser powder bed fusion (LPBF) is investigated. We observed minor differences in the viscous flow of the specimens fabricated by the different techniques that can be ascribed to the higher porosity of the LPBF metallic glass. Nevertheless, the present results reveal a similar overall variation of viscosity in the cast and LPBF materials, which offers the opportunity to shape additively manufactured BMGs using already developed thermoplastic forming techniques.

Elucidating the Relationship Between Structure and Property of Waterborne Polyurethane-Cellulose Nanocrystals Nanocomposite Films

Cellulose nanocrystals (CNCs) are promising polymer reinforcements owning to their biocompatibility and high elastic modulus, low density, nano size, and inherent biocompatibility. The waterborne polyurethane-cellulose nanocrystals (WPU-CNCs) nanocomposite films were prepared using the conventional solvent casting technique over a whole composition. The mechanical performance, optical transmittance, amphiphilicity, water vapor permeability (WVP), and oxygen permeability (OP) of these WPU-CNCs films were evaluated. The incorporation of CNCs into WPU resulted in a significant enhancement of Young's modulus and tensile strength. The WVP of nanocomposite films had a lowest value at CNCs content of 50 wt.%. Upon the increase of CNCs content from 0 to 90 wt.%, the transmission path of oxygen molecular through the nanocomposite films became more tortuous, leading to drastic decrease in the OP. These WPU-CNCs nanocomposite films with high strength, optical transparency, water vapor and oxygen barrier properties have the potential applications in biomedical, furniture coating, and food packaging fields.

Investigation of the machinability of SiC reinforced MMC materials produced by molten metal stirring and conventional casting technique in die-sinking electrical discharge machine

In this study, MMC materials were produced by stir casting method using AA7075 alloy matrix and silicon carbide (SiC) as reinforcement elements in order to investigate the effect of die-sinking electric discharge machining (EDM) process parameters for various weight percentage reinforcement (10% 14% and 18%) used MMC. EDM with three different pulse-on time (Time on) (25, 50 &75 µs) and discharge current value (2, 4 & 6 Amperes) and at constant dwell time (20 µs) and depth of cut (0.5 mm). After machining process, the effects of process parameters on processing time, average surface roughness, hole diameter and the weight loss were investigated. As a result of the study, highest values, the lowest values of processing time, hole diameter and average surface roughness were obtained for various weight percentage reinforcement MMC respectively. Ideal MMC, discharge current value and time-on duration for average surface roughness, hole diameter, processing time and material wear loss according to signal to noise ratio were determined. According to ANOVA results, R2 values for the average surface roughness, hole diameter, processing time and material wear loss were calculated as 89.55%, 98.46%, 89.85% and 24.06% respectively.