Conventional Casting Process Research Articles

Very high cycle fatigue properties at 973 K of additively manufactured and conventionally processed intermetallic TiAl 48-2-2 alloy

The fatigue lives of 2nd generation γ-TiAl alloy Ti–48Al–2Cr–2Nb manufactured both by additive manufacturing using electron beam powder bed fusion (EB-PBF) as well as conventional casting process by vacuum arc remelting for comparison (REF) were investigated. Both batches (EB-PBF and REF) were subject to the common treatment process, i.e. hot isostatic pressing and heat treatment to achieve a duplex microstructure. As a result, a fine- and a coarse-grained microstructure consisting of γ-grains and colonies of α2/γ lamellae have evolved for the EB-PBF and conventionally cast material, respectively. Uniaxial fatigue tests were performed in the very high cycle fatigue (VHCF) range up to 109 cycles at a load ratio of R = −1 using ultrasonic fatigue testing equipment at an elevated temperature of 973 K. The SN data of both batches were discussed with respect to the influence of microstructure and temperature on the processes of crack initiation and propagation. The additive manufactured material showed superior fatigue strength compared to the conventional material due to its smaller grain size. It was shown that the fine-grained duplex microstructure of the batch EB-PBF is particularly appropriate to decrease short crack propagation at elevated temperatures due to its microstructural characteristics.

Hot isostatic pressing of Cu–15Ni–8Sn alloy with suppressed Sn macro-segregation and enhanced mechanical properties

Sn macro-segregation and coarse grains easily occur in the conventional casting process of the Cu–15Ni–8Sn alloy with a high Sn content. Here, hot isostatic pressing (HIP), an advanced powder metallurgy technique, was introduced to explore feasibility in alleviating or eliminating such defects. The gas–atomized powder with high homogeneity of composition was used, which was solidified rapidly. The microstructural evolution, mechanical properties, deformation mechanisms and strengthening mechanisms were deeply and systematically revealed and discussed. Nearly fully dense samples were fabricated by HIP with no Sn macro-segregation, and simultaneous strength-plasticity enhancement was obtained. The content of harmful discontinuous precipitation colonies was controlled to only ∼3.11 vol%. This was attributed to the fine grain size of the powder and the preferential complete recrystallization process during the HIP. That is, the γ nucleation sites were occupied by numerous grain boundaries provided by fine grains, and the driving force of γ growth was consumed by recrystallization. Furthermore, enhanced mechanical properties were related to the Sn macro-segregation suppression, grain refinement (∼11.0 μm), dislocation density continuous increase, and dispersion distribution of γ precipitates, etc. These encouraging findings validate the advantages and potential of HIP in the fabrication of Cu–15Ni–8Sn alloy with enhanced mechanical properties for structural applications.

Microstructure Study and Linear/Nonlinear Optical Performance of Bi-Embedded PVP/PVA Films for Optoelectronic and Optical Cut-Off Applications.

Hybrid polymer films of polyvinyl pyrrolidone (PVP)/polyvinyl alcohol (PVA) embedded with gradient levels of Bi-powder were prepared using a conventional solution casting process. XRD, FTIR, and SEM techniques have been used to examine the micro/molecular structure and morphology of the synthesized flexible films. The intensities of the diffraction peaks and transmission spectrum of the PVP/PVA gradually declined with the introduction of Bi-metal. In addition, filler changes the microstructure surface of the pure film. The modification in the microstructure leads to an enhancement in the optical absorption characteristic of the blend films. The indirect allowed transition energy was calculated via Tauc’s and ASF (Absorption Spectra Fitting) models. The decrease in the hybrid film’s bandgap returns to the localized states in the forbidden region, which led the present films to be suitable for photo-electric, solar cell, etc., applications. The relation between the transition energy and the refractive index was studied. The enhancement in the refractive index with Bi-metal concentrations led to use the as-prepared films in optical sensors. The rise of Bi-metal concentrations leads also to the improvement of the nonlinear susceptibility and refractive parameters. The optical limiting characteristics revealed that the higher concentration dopant films reduce the light transmission intensity which is appropriate for laser attenuation and optical limiting in photonic devices. The results suggest that hybrid films are promising materials in a wide range of opto-electronic applications.

Microstructure evolution of Al-Si hypoeutectic alloys prepared by controlled diffusion solidification

The possibility of changing the dendritic microstructure associated with the conventional casting processes of hypoeutectic Al-Si alloys to non-dendritic microstructure by using the controlled diffusion solidification process (CDS) has been investigated. The successful CDS process depends on mixing two precursor alloys heated at a superheat condition near their respective liquidus temperature. Experimental work and simulation work using Ansys software were carried out in the present study by employing Al-Si and Al-Cu systems. This study investigates the effect of the content of the two precursor alloys, the mass ratio changing from 2.6 to 8.3, and the superheat of the first precursor alloy on changing the microstructure. The experimental results show that the pure aluminum used as the first precursor alloy needs more undercooling and agitation during the mixing to form the non-dendritic microstructure compared with hypoeutectic Al-Si alloys. Furthermore, mixing pure aluminum with hypereutectic alloy can change the microstructure of hypoeutectic alloys leading to extending the possibility to choose the second precursor alloy. The results also show that a higher mass ratio is preferred when mixing pure aluminum with hypoeutectic alloy. Furthermore, the microstructure of the alloy Al- 6.45Si- 4Cu- 0.5 Mg- 0.66Fe- 0.66 wt%Zn was successfully changed via the CDS process by mixing Al- 7.75Si- 0.79Fe- 0.78Zn- 0.6 wt%Mg at 2 °C superheat into Al-24 wt%Cu at around 5 °C superheat. The simulation results show that lower air bubbles and better distribution of the two precursor alloys happen during the mixing step when using the Al-Cu system.

Stretchable and Flexible Non‐Enzymatic Glucose Sensor Based on Poly(ether sulfone)‐Derived Laser‐Induced Graphene for Wearable Skin Diagnostics

AbstractThe laser‐induced graphene (LIG) has a great potential in electrochemically active electrodes for wearable biosensors. Herein, for the first time, a stretchable and non‐enzymatic glucose sensor based on LIG derived from commercial poly(ether sulfone) (PES) membranes is reported. The LIG is in situ transferred onto an elastomer and tightly wrapped by the elastomer in one laser carbonization step. Superior to the conventional casting and demolding transfer process, this method avoids the LIG's morphology distortion and loss. By adjusting the laser settings and the patterns, hierarchically structured electrodes are prepared with greatly increased surface areas for glucose detection. The electrodeposited dendritic gold‐nanoparticles act as the catalyst for glucose sensing. The optimized flexible sensor demonstrates a linear range for glucose from 10 μm to 10.0 mm and a detection limit of 26 μm. The sensor shows a sensitivity of 0.024 ± 0.001 mA mm−1 and selectivity toward other interfering metabolites, as well as excellent performance under mechanical bending (stable performance after 500 bending cycles) and stretchability (resistance unchanged after 1000 cyclic stretching at 20% strain). Due to the simplicity of preparation and extraordinary fidelity, the novel PES‐LIG sensor is a promising candidate for the next generation of skin‐adherent diagnostic devices and wearable electronics.

Induction melting of an Al-50Cu alloy for improved homogeneity required for powder spheroidisation

Copper alloys are typically produced by conventional casting processes, including spark plasma sintering (SPS), which often produce inhomogeneous mixtures of Cu or Al precipitates and unwanted intermetallic phases in solid products. Induction melting should provide good mixing, controlled heating and melt stirring, potentially improving homogeneity. Homogeneous melts should produce homogeneous powders, giving better properties in additive manufacturing (AM). To ascertain homogeneity, a density test was developed. After comminution, homogeneous powders can be used to produce high quality components. To manufacture dense AM components, spheroidised powders are needed because they increase particle packing and powder flow. An Al-50Cu (at.%) button was produced by high-frequency (HF) induction melting, to give better mixing and hence phase distributions. To identify the phases and their distributions, the as-cast sample was studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), as well as absolute density using helium pycnometry. Results indicated inhomogeneity in the samples, due to Al loss, complex solidification and the densest phase settling at the bottom of the button.

Al Alloys and Casting Processes for Induction Motor Applications in Battery-Powered Electric Vehicles: A Review

With the rapid expansion of battery-powered electric vehicles (BEVs) in the automotive industry, research interest in lightweight Al alloys as well as their casting processes and applications has increased considerably. The substitution of castable aluminum alloys with superior strengths and electrical conductivity for copper reduces the weight and size of electric induction motors, and improves the energy efficiency and driving range of the BEVs. The present article was intended to give a general introduction into the common cast Al aluminum alloys and their relevant processes, as well as to motivate the development of high strength and conductive Al alloys for the practical realization of Al applications in the motors of the BEVs. A number of cast alloy systems containing Cu, Si, Ni, Mg, Fe, and Ti were evaluated, in comparison to nanostructured wrought Al alloys. The conventional casting processes suitable for Al alloys, high pressure die casting, squeeze casting, and sand casting were described. Strengthening mechanisms including solid solution strengthening, precipitation strengthening, dislocation accumulation strengthening, and grain boundary strengthening were presented. The phenomenon of electrical conduction for Al alloys was outlined. The mechanical properties and electrical properties of the recently developed Al alloys for casting and deformation processes were comprehensively listed and critically reviewed in association with microstructural characteristics.

Application of ultrasounds to improve the dispersion of nanoparticulates in a Al-Si7Mg0.6 alloy reinforced with 0.5 wt. % of nanodiamonds

One of the most important technical barriers that hinders the development and implementation of nanoparticulate reinforced aluminium alloys is the difficulty to avoid the formation of clusters and to obtain their homogeneous distribution. The present work summarises the results obtained with the use of an ultrasound probe that was immersed into the melt alloy containing nanodiamond particulates just before the casting step. The microstructure and tensile properties of the obtained specimens are compared with nanoreinforced samples obtained with conventional stir cast process. The materials used in the study are the Al-Si7Mg0.6 casting alloy and nanodiamond particulates obtained by detonation synthesis. Samples containing up to 0.5 wt.% of nanodiamonds have been obtained. The use of the ultrasound probe results in the elimination of nanoparticulate clusters and provides an improvement of mechanical properties in comparison to properties measure with the unreinforced alloy and also with the conventionally stir cast composite.

Ablation technology applied to A356 alloys compared with conventional casting processes

Because ablation differs from conventional casting, some conventional metallurgical concepts, such as the relationship among secondary dendrite arm spacing (SDAS), microconstituents and tensile properties, should be revised.To understand the mechanisms governing ablation technology, the most popular of casting alloys, A356 alloys, were selected, and conventional melt treatments, such as degassing, grain refinement and Si modification with Sr, were applied. All ablated as-cast microstructural characteristics (SDAS, grain size, porosity, Si particle morphology and Fe-bearing phases) and the mechanical properties after T6 were compared with two conventional processes: permanent moulding and sand cast manufacturing with the same metal. SDAS values, which are commonly used to predict mechanical properties in conventional casting processes, are no longer valid for ablation, which presents coarse SDAS microstructures, similar to those obtained with the conventional sand casting process, with some isolated areas of fine SDASs. However, the high freezing rate in the last stage of the solidification process obtained by ablation technology generates fine eutectic Si and iron-bearing particles and low porosity. This makes it possible to obtain quality index values of Q = 480 MPa that are significantly higher than those of sand casting (Q = 426 MPa) and similar to those obtained for permanent moulds (Q = 480 MPa).Additionally, the potential advantages of ablation for T5 (Q = 419 MPa) and shorter solution time T6 treatments (Q = 479 MPa) were also investigated in terms of mechanical properties and Si particle size and shape.

Experimental Investigation on Mechanical Properties of Part Fabricated by Wire Arc Additive Manufacturing Process

Additive manufacturing process is a method of layer by layer joining of materials to create components from three-dimensional (3D) model data. After their introduction in the automotive sector a decade ago, it has seen a significant rise in research and growth. The Additive manufacturing is classified into different types based upon the energy source use in the fabrication process. In our project, we used self-build CNC machine that runs MACH3 software, as well as the MACH3 controller is used to control the welding torch motion for material addition through three axis movement (X, Y and Z). In the project we used ER70 S-6 weld wire for the fabrication and examined its microstructure and mechanical properties. Different layers of the specimen had different microstructures, according to microstructural studies of the product. Rockwell hardness tester used for testing hardness of the product. According to the observation of the part fabricated components using the Wire Arc Additive Manufacturing process outperformed the mechanical properties of mild steel casting process. The product fabricated by Wire Arc Additive Manufacturing process properties is superior to conventional casting process.

Microstructure Characteristics and Strengthening Behavior of Cu-Bearing Non-Oriented Silicon Steel: Conventional Process versus Strip Casting

Based on conventional hot rolling processes and strip casting processes, Cu precipitation strengthening is used to improve the strength of non-oriented silicon steel in order to meet the requirements of high-speed driving motors of electric vehicles. Microstructure evolution was studied, and the effects of Cu precipitates on magnetic and mechanical properties are discussed. Compared with conventional processes, non-oriented silicon steel prepared by strip casting exhibited advantages with regard to microstructure optimization with coarse grain and {100} texture. Two-stage rolling processes were more beneficial for uniform microstructure, coarse grains and improved texture. The high magnetic induction B50 of 1.762 T and low core losses with P1.5/50, P1.0/400 and P1.0/1000 of 1.93, 11.63 and 44.87 W/kg, respectively, were obtained in 0.20 mm sheets in strip casting. Cu precipitates significantly improved yield strength over ~120 MPa without deteriorating magnetic properties both in conventional process and strip casting. In the peak stage aged at 550 °C for 120 min, Cu precipitates retained bcc structure and were coherent with the matrix, and the yield strength of the 0.20 mm sheet was as high as 501 MPa in strip casting. The main mechanism of precipitation strengthening was attributed to coherency strengthening and modulus strengthening. The results indicated that balanced magnetic and mechanical properties can be achieved in thin-gauge non-oriented silicon steel with Cu addition in strip casting.

Simulation studies on melting characteristics of bulk alloy Al-1050 during in-situ microwave casting process

The metal casting process is one of the industry's most significant production processes and is also one of the eco-friendly techniques for making usable parts. Metal smelts are the main melting process that takes several stages. However, concerning increased energy consumption, longer casting periods, and major failures, the conventional casting process does have significant problems. New methods are being developed to address these deficiencies of classic casting procedures. The technique of microwave casting is one of the innovative methods that satisfy current needs in the business. The process involves complexity of understanding the heating rate, material interaction phenomenon etc. A 3-D model of the in situ casting process was generated through COMSOL multiphysics software tool. A complete simulation based studies were carried out to predict the thermal history of the metal melting. The simulation results obtained by considering various power levels (1500 W to 3500 W) to predict melting time, average heating rate, desired energy to melt the materials. It was observed that the role of electric field distribution inside the microwave applicator and distribution of the temperature in the charge play a important role at hot spot condition and also to increase in temperature in the charge. It is noted that energy decreases are 15.37% at 3500 W, 9.8% at 2000 W, 16.67% at 2500 W, and 13.6% at 3000 W. Finally, the simulation data showed that the heating of the bulk metal is rapid and consistent at specific location of the mold assembly.

Increased tensile strength and elongation of the Ni–Fe based polycrystalline cast superalloy via the trace addition of TiC nanoparticles

In this work, a Ni–Fe based cast superalloy (K214) containing 0.02 wt% TiC nanoparticles was fabricated by the vacuum induction melting, and the effects of TiC nanoparticles on the microstructure and tensile properties of the alloys were investigated. The trace addition of TiC nanoparticles effectively refined the as-cast grains, promoted the coarsening of secondary dendrite arms, and reduced microsegregation. The yield strength, ultimate tensile strength and elongation at room/elevated temperatures were simultaneously improved, which could be ascribed to reduced microsegregation and refined γ′ precipitates. This work provides a strategy for the effective improvement in the mechanical properties of cast superalloys fabricated by the conventional casting process.

Patterned mesoporous TiO2 microplates embedded in Nafion® membrane for high temperature/low relative humidity polymer electrolyte membrane fuel cell operation

Incorporating inorganic fillers, such as SiO2, TiO2, and CeO2, into the electrolyte membrane via the conventional casting and evaporation process is proved to intensify the water retention, thus improve the proton conductivity of the polymer electrolyte membrane (PEM) under high temperature. However, this approach does not dramatically enhance the performance of the composite membrane due to the issue of proton pathway reduction and fillers agglomeration. Herein, uniformly patterned mesoporous TiO2 microplates (PTMPs) are successfully embedded on the anode side surface of the Nafion® membrane by using micro-hole stencil for spatially localizing the PTMPs and well-controlled ionomer spray technique. Interestingly, the membrane comprised of PTMPs with a diameter of ∼50 μm and a height of ∼5.2 μm exhibits the maximum power density by more than 35.2% compared to the reference Nafion® membrane with the same thickness (∼25 μm) under 120 °C and relative humidity of 35% condition. The result indicates that suitably designed PTMPs-embedded Nafion® membrane is effective for improving the PEMFC performance under elevated temperature and low humidity conditions.

A comparison of the microstructures and hardness values of non-equiatomic (FeNiCo)-(AlCrSiTi) high entropy alloys having thermal histories related to laser direct metal deposition or vacuum remelting

Compared with conventional casting process, laser direct metal deposition (LDMD) can effectively reduce component segregation in non-equiatomic high entropy alloys (HEAs). However, the non-equilibrium thermal history imparted by this method has a significant effect on the microstructure and mechanical properties of the HEA. The present work prepared non-equiatomic (FeNiCo)-(AlCrSiTi) HEAs using the LDMD process, after which some samples were subjected to a subsequent vacuum remelting (VRM) treatment. The variations in phase composition, microstructure and hardness between the HEAs processed using the LDMD or VRM methods were investigated. Differences in phase composition increased with increases in the proportion of the Al, Cr, Si and Ti components. Compared with the HEA samples processed using the VRM method, the LDMD specimens possessed much finer and simpler microstructures mainly comprising solid solution phases. At relatively high concentrations of the Al, Cr, Si and Ti components (32 at% and 40 at% in total), the HEAs processed under LDMD conditions had similar grain morphologies, intermetallic phases and microhardness values, while the VRM specimens presented completely different microstructures and properties.

Study on Mechanical Properties of AA6061/SiC/B<sub>4</sub>C Hybrid Nano Metal Matrix Composites

The present work investigates the mechanical characterization of aluminium alloy (AA) 6061 based hybrid nanometal matrix composites (MMCs) fabricated using conventional stir casting process. Two compositions viz., AA6061+1.5 wt.% B4C+0.5 wt.% SiC (Hybrid A) and AA6061+1.5 wt.% B4C+1.5 wt.% SiC (Hybrid B) was prepared and its mechanical properties such as microhardness, tensile, compressive, flexural and impact strength were investigated to compare with unreinforced AA6061. SiC and B4C ceramic particles (purity 99.89%) of average particle size of 50 nm were used as reinforcements. Significant enhancement in microhardness of 30.2% and 31.02% for hybrid A and B are observed respectively. The ultimate tensile strength (UTS) increased by 10.72% and 16.55% for hybrid A and B respectively. Improved interaction because of the enhanced surface to volume ratio at the interface resulted in improvement of mechanical properties. Field emission scanning electron microscopy (FESEM) of the fractured surface shows brittle fracture because of the incorporation of the ceramic reinforcements in the matrix material. The developed AA6061/SiC/B­4C hybrid nanocomposites show improved mechanical properties for high-performance structural applications.

Comparison of Ni-Cr based partial dentures prepared by thermoplastic and wax based investment casting: Mechanical, morphological and in-vitro analysis

The Ni-Cr (Y) alloys are being extensively used for the manufacture of commercial partial dentures (PDs). In this study, five different routes of developing master patterns (including conventional wax, computer-aided manufactured wax, three-dimensional printed (3DP) thermoplastic, wax coated 3DP thermoplastic, and acetone treated 3DP thermoplastic) have been compared for the development of Y-alloy based PDs through conventional investment casting (IC) process. The finally developed PDs have been compared for their geometrical (dimensional accuracy and surface roughness), mechanical (micro-hardness), and morphological (optical and scanning electron microscopy (SEM) analysis). Moreover, the in-vitro corrosion and cell-culture properties of the developed PDs have also been analyzed. The overall results of the study highlighted that depending on the merits offered by the master pattern, the PDs can be developed for superior dimensional accuracy, surface finish, micro-hardness, corrosion resistance, and biocompatibility.

Microstructure and magnetic properties of ultra-thin grain-oriented silicon steel: Conventional process versus strip casting

Ultra-thin grain-oriented silicon steels were processed via the conventional process and strip casting process, and the mechanisms of texture inheritance and inhibitor induced secondary recrystallization were comparatively studied in detail. In the conventional route with commercial grain-oriented silicon steel as the starting material, exact {111} 〈112〉 dominated the deformation texture after cold rolling with ~ 63% reduction, and strong Goss texture was formed in 0.08–0.10 mm thin-gauge primary recrystallized sheet. Meanwhile, weak {210} 〈001〉 and {h11} < 1/h12 > textures were also observed because of the inhomogeneous deformation with initial deviated Goss texture. After high temperature annealing, the sheet experienced incomplete secondary recrystallization with abnormal growth of Goss grains accompanied by normal growth of {210} 〈001〉 and {411} 〈148〉 grains, considering the absence of pinning force on grain boundary migration. In the strip casting process, the intensity of γ-fiber texture was increased, while grain size decreased from ~ 13.3 to ~11.4 μm and the area fraction of Goss grains decreased from 2.8% to 0.6% in the primary recrystallized sheet with decrease of thickness from 0.15 to 0.08 mm. During high temperature annealing process, MnS, (Nb,V)N and AlN provided continuous and sufficient inhibition force for normal grain growth, which guaranteed the formation of complete secondary recrystallization of exact Goss grains. Superior magnetic induction B8 was up to 1.97 T in the strip casting process, which was 0.09 T higher than the conventional route. Meanwhile, the iron losses P1.7/50 and P1.0/1000 were as low as 0.85 and 20.7 W/kg, respectively, which were comparable to the reported ultra-thin grain-oriented silicon steels. The present study provided a novel method to produce high efficiency ultra-thin grain-oriented silicon steel, which may significantly contribute to energy saving in high-frequency electrical devices.

The effect of composition on microstructure and properties for additively manufactured superalloy 718

Additive manufacturing (AM) represents an exciting new approach towards producing metallic aerospace components. The ability to make complex geometries that were impossible to create using conventional manufacturing methods has sparked interest from the aerospace community, including NASA. The use of AM components for crucial and human rated space missions necessitates a full characterization of the differences between AM and more conventional wrought and cast processes. For this study, sixteen different commercially available superalloy 718 powder feedstocks were obtained, built using laser powder bed fusion (L-PBF), and microstructurally and mechanically analyzed. These measurements revealed a wide range of build qualities and microstructures despite all powder lots falling within the 718 chemical specification and being processed using the same prescribed build and heat treatment parameters. Statistical analysis found a strong correlation of the amount of carbon in the powder with the final grain size and strength of the heat-treated 718 part. Ultimately, this study highlights the need of a refined superalloy 718 chemical specification for powder lots to be used in AM.

Comparative Study on Morphological, Physical and Mechanical Characteristics of L-PBF Based AlSi10Mg Parts with Conventional Stir Casted Al-10 %SiC Composites

Stir casting plays a major role in the production of Al-SiC10 % composites for aero space and automobile applications. However, obtaining the composites with homogenous distribution of the SiC particles, low porosity and without clustering of reinforcement particles are still a major problem faced by the research community. These kind of casting defects were overcome by the Additive Manufacturing (AM) technology. In this research, AlSi10Mg parts were manufactured by Laser-Powder Bed Fusion (LPBF) method, one of the AM techniques. The mechanical and morphological characteristics of Additive manufactured (AM) samples were compared with the Stir Casted (SC) samples. Both AM and SC samples were analyzed for the porosity% using the Optical Microscope (OM). From the porosity analysis, it was evident that the AM samples shows 14 % reduction in porosity when compared with the SC samples. Mechanical testing such as tensile test, hardness test, fracture toughness test and double shear stress were carried out. The results obtained from the tensile test reveals that the AM samples shows 28.6 % higher tensile strength than the SC samples. Similarly, the hardness test for the AM samples shows 23.69 % higher hardness strength than the SC samples. The fracture toughness test for the AM samples shows 50 % higher fracture toughness strength than the SC samples and from the results of double shear stress test proves that the AM samples shows 32.55 % higher shear stress than the SC samples. The outcome of this research proved that additive manufactured AlSi10Mg sample shows enhanced mechanical and morphological properties when compared with the conventional stir casting process.