Melting Casting Research Articles

Effects of process parameters on surface quality, composition segregation, microstructure and properties of QSn6. 5-0. 1 alloy slabs fabricated by HCCM horizontal continuous casting

Columnar-grained QSn6. 5-0. 1 alloy slabs with a width of 70 mm and thickness of 10 mm were fabricated by heating-cooling combined mold (HCCM) horizontal continuous casting. The effects of process parameters on solidification microstructure, surface quality, composition segregation and mechanical properties were studied. The results showed that the slabs with good surface quality, excellent mechanical properties and no obvious segregation could be prepared at the melt casting temperature of 1250 °C, the heating-mold temperature of 1150—1200 °C, the cooling water flow rate of 600 L/h and the casting speed of 20—80 mm/min. The slabs had the yield strength of 124—155 MPa, the elongation rate of 46.6%—56.3% and the surface roughness of 0.22—0.55 μm, which enabled them to be directly processed without subsequent milling surface. The ratio of Sn content in the surface to that in the core was 0.83—1.10, with an average value close to 1.0, and not obviously influenced by process parameters. When the casting speed increased from 20 to 80 mm/min, the grain size changed little if the other process parameters were the same. When the heating-mold temperature increased from 1150 to 1200 °C, the grain size was obviously refined and became more uniform if the casting speed was the same. Within the range of the casting speed at which the columnar grain structure could be obtained, the columnar grain size was mainly influenced by the heating-mold temperature.

Degradation behavior and mechanical strength of Mg-Zn-Ca bulk metallic glass composites with Ti particles as biodegradable materials

MgZnCa-based alloys have great potential as implant materials due to their non-cytotoxicity, ease of degradation in the human body, and a low Young's modulus close to that of bone. However, there are few reports on their long-term degradation behavior and the mechanical properties resulting from degradation. This study thus aims to explore the long-term degradation behavior and mechanical strength of Mg60Zn35Ca5 and Mg67Zn28Ca5 bulk metallic glass (BMG) and its composites with Ti particles (BMGCs) before and after immersion in simulated body fluid (SBF). Rods of Mg60Zn35Ca5 and Mg67Zn28Ca5 BMG and their corresponding composites BMGCs have been prepared through an induction melting and injection casting method. Then, their degradation behavior, surface morphology, microstructure, mechanical properties, and biocompatibility have been systematically investigated. The results show that Mg60Zn35Ca5 BMGC has the lowest degradation rate (0.26 mm/year) after 12 weeks of immersion. It has a compressive strength of 807 MPa initially and 154 MPa after 12 weeks of immersion. In this study, all samples are classed as slightly toxic based on the standard ISO 10993-5.

Study on the synthesis of 2-fluoro-2,2-dinitroethyl esters as a potential melt cast matrix in explosive charges

Polynitro energetic compounds with low melting points, high thermal stabilities, good detonation properties, and considerably mechanical insensitivities are reported; some of these compounds are promising potential replacements of TNT used in melt cast explosives.

Study on a novel high energetic and insensitive munitions formulation: TKX-50 based melt cast high explosive

Dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) is a promising candidate to replace traditional explosives, HMX and RDX, used in insensitive munitions, which is currently being explored to achieve shock insensitive melt cast formulations.

Diclofenac sodium ion exchange resin complex loaded melt cast films for sustained release ocular delivery

Purpose: The goal of the present study is to develop polymeric matrix films loaded with a combination of free diclofenac sodium (DFSfree) and DFS:Ion exchange resin complexes (DFS:IR) for immediate and sustained release profiles, respectively.Methods: Effect of ratio of DFS and IR on the DFS:IR complexation efficiency was studied using batch processing. DFS:IR complex, DFSfree, or a combination of DFSfree + DFS:IR loaded matrix films were prepared by melt-cast technology. DFS content was 20% w/w in these matrix films. In vitro transcorneal permeability from the film formulations were compared against DFS solution, using a side-by-side diffusion apparatus, over a 6 h period. Ocular disposition of DFS from the solution, films and corresponding suspensions were evaluated in conscious New Zealand albino rabbits, 4 h and 8 h post-topical administration. All in vivo studies were carried out as per the University of Mississippi IACUC approved protocol.Results: Complexation efficiency of DFS:IR was found to be 99% with a 1:1 ratio of DFS:IR. DFS release from DFS:IR suspension and the film were best-fit to a Higuchi model. In vitro transcorneal flux with the DFSfree + DFS:IR(1:1)(1 + 1) was twice that of only DFS:IR(1:1) film. In vivo, DFS solution and DFS:IR(1:1) suspension formulations were not able to maintain therapeutic DFS levels in the aqueous humor (AH). Both DFSfree and DFSfree + DFS:IR(1:1)(3 + 1) loaded matrix films were able to achieve and maintain high DFS concentrations in the AH, but elimination of DFS from the ocular tissues was much faster with the DFSfree formulation.Conclusion: DFSfree + DFS:IR combination loaded matrix films were able to deliver and maintain therapeutic DFS concentrations in the anterior ocular chamber for up to 8 h. Thus, free drug/IR complex loaded matrix films could be a potential topical ocular delivery platform for achieving immediate and sustained release characteristics.

Influence of crystallization conditions on the structure and modifying ability of Al–Sc alloys

The influence of the modes of thermal-and-temporal treatment and cooling rate of metallic alloys on crystallization regularities of Al–Sc alloys and their structure, properties, and modifying ability are established. Castings of Al–Sc alloy, which were prepared by the electrolysis of salt melts KF–NaF–AlF3–Sc2O3 at 820–850°C, are used as the initial charge for casting. It is established that, by varying the magnitude of melt overheating and casting temperature, it is possible to vary the crystal shape, amount, and size in wide limits. The modifying action of cast and rapidly quenched master alloys, as well as the master alloy produced by electrolysis, is tested for Al–4.5% Cu alloy. The largest effect of milling the structure of the Al–4.5% Cu–0.4% Sc alloy is attained when using the rapidly quenched master alloy.

Characterization of phase changes during fabrication of copper alloys, crystalline and non-crystalline, prepared by mechanical alloying

The manufacture of alloys in solid state has many differences with the conventional melting (casting) process. In the case of high energy milling or mechanical alloying, phase transformations of the raw materials are promoted by a large amount of energy that is introduced by impact with the grinding medium; there is no melting, but the microstructural changes go from microstructural refinement to amorphization in solid state. This work studies the behavior of pure metals (Cu and Ni), and different binary alloys (Cu-Ni and Cu-Zr), under the same milling/mechanical alloying conditions. After high-energy milling, X ray diffraction (XRD) patterns were analyzed to determine changes in the lattice parameter and find both microstrain and crystallite sizes, which were first calculated using the Williamson-Hall (W-H) method and then compared with the transmission electron microscope (TEM) images. Calculations showed a relatively appropriate approach to observations with TEM; however, in general, TEM observations detect heterogeneities, which are not considered for the W-H method. As for results, in the set of pure metals, we show that pure nickel undergoes more microstrain deformations, and is more abrasive than copper (and copper alloys). In binary systems, there was a complete solid solution in the Cu-Ni system and a glass-forming ability for the Cu-Zr, as a function of the Zr content. Mathematical methods cannot be applied when the systems have amorphization because there are no equations representing this process during milling. A general conclusion suggests that, under the same milling conditions, results are very different due to the significant impact of the composition: nickel easily forms a solid solution, while with a higher zirconium content there is a higher degree of glassforming ability.

Vertikalno kontinuirno litje NiTi zlitine

In this paper we present research that is connected to the performance of a series of experiments combined with the vacuum-induction melting and continuous vertical casting of a NiTi alloy in order to produce the strand. The theoretical chosen parameters made it possible to obtain a continuously cast strand with a diameter of 11 mm. The strand microstructures were investigated with a light and scanning electron microscope, while the chemical composition of the single phase was identified with the semi-quantitative micro-analysis energy-dispersive X-ray spectroscopy and inductively coupled plasma – optical emission spectrometry. The research showed that the microstructure is dendritic, where in the inter-dendritic region the eutectic is composed of a dark NiTi phase and a bright TiNi3–x phase. In some areas we found Ti carbides and phases rich in Fe. The micro-chemical analysis of the NiTi strand showed that the composition changed over the cross and longitudinal sections, which is proof that the as-cast alloys are inhomogeneous. In the final part, the electrochemical behaviours of NiTi strand samples were compared to a commercially available NiTi cast alloy with the same composition.

Determination of the hardness and the mechanical properties of steel during melting, secondary refining, and continuous casting in an arc-furnace shop

The density and the ultimate tensile strength of steel are studied during melting, secondary refining, and continuous casting in an arc-furnace shop.

Ocular Disposition of ∆8-Tetrahydrocannabinol from Various Topical Ophthalmic Formulations.

The purposes of this project are to enhance the trans-membrane penetration of Δ8-Tetrahydrocannabinol (Δ8-THC) and to study the effect of various lipid based systems in delivering the compound, non-invasively, to anterior and posterior ocular chambers. Solid lipid nanoparticles (SLNs), fast gelling films were manufactured using high pressure homogenization and melt cast techniques, respectively. The formulations were characterized for drug content, entrapment efficiency, particle size and subsequently evaluated in vitro for trans-corneal permeation. In vivo, the drug disposition was tested via topical administration in albino rabbits. The eye globes were enucleated at the end of experiment and tissues were analyzed for drug content. All formulations showed favorable physicochemical characteristics in terms of particle size, entrapment efficiency, and drug content. In vitro, the formulations exhibited a transcorneal flux that depended on the formulation's drug load. An increase in drug load from 0.1 to 0.75% resulted in 12- to16-folds increase in permeation. In vivo, the film was able to deliver THC to all the tissues with high accumulations in cornea and sclera. The SLNs showed a greater ability in delivering THC to all the tissues, at a significantly lower drug load, due to their colloidal size range, which in turn enhanced corneal epithelial membrane penetration. The topical formulations evaluated in the present study were able to successfully deliver Δ8-THC in therapeutically meaningful concentrations (EC50 values for CB1: 6nM and CB2: 0.4nM) to all ocular tissues except the vitreous humor, with pronounced tissue penetration achieved using SLNs as a Δ8-THC delivery vehicle.

A Self-Binding, Melt-Castable, Crystalline Organic Electrolyte for Sodium Ion Conduction.

The preparation and characterization of the cocrystalline solid-organic sodium ion electrolyte NaClO4 (DMF)3 (DMF=dimethylformamide) is described. The crystal structure of NaClO4 (DMF)3 reveals parallel channels of Na+ and ClO4- ions. Pressed pellets of microcrystalline NaClO4 (DMF)3 exhibit a conductivity of 3×10-4 S cm-1 at room temperature with a low activation barrier to conduction of 25 kJ mol-1 . SEM revealed thin liquid interfacial contacts between crystalline grains, which promote conductivity. The material melts gradually between 55-65 °C, but does not decompose, and upon cooling, it resolidifies as solid NaClO4 (DMF)3 , permitting melt casting of the electrolyte into thin films and the fabrication of cells in the liquid state and ensuring penetration of the electrolyte between the electrode active particles.

A Self‐Binding, Melt‐Castable, Crystalline Organic Electrolyte for Sodium Ion Conduction

AbstractThe preparation and characterization of the cocrystalline solid–organic sodium ion electrolyte NaClO4(DMF)3 (DMF=dimethylformamide) is described. The crystal structure of NaClO4(DMF)3 reveals parallel channels of Na+ and ClO4− ions. Pressed pellets of microcrystalline NaClO4(DMF)3 exhibit a conductivity of 3×10−4 S cm−1 at room temperature with a low activation barrier to conduction of 25 kJ mol−1. SEM revealed thin liquid interfacial contacts between crystalline grains, which promote conductivity. The material melts gradually between 55–65 °C, but does not decompose, and upon cooling, it resolidifies as solid NaClO4(DMF)3, permitting melt casting of the electrolyte into thin films and the fabrication of cells in the liquid state and ensuring penetration of the electrolyte between the electrode active particles.

An Experimental Study of Thermophysical Properties for Quinary High-Entropy NiFeCoCrCu/Al Alloys**Supported by the National Natural Science Foundation of China under Grant Nos 51571163, 51371150, 51271150 and 51327901

Two quinary high-entropy alloys (HEAs) with equiatomic concentrations formed by doping either Cu or Al elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entropy of fusion, thermal expansion coefficient and thermal diffusivity are experimentally investigated with differential scanning calorimetry, dilatometry and laser flash methods. The NiFeCoCrCu HEAs contain a face-centered cubic high-entropy phase plus a minor interdendritic (Cu) phase and display a lower entropy of fusion and the Vickers hardness. The NiFeCoCrAl HEAs consist of two body-centered cubic high-entropy phases with coarse dendritic structures and show higher entropy of fusion and the Vickers hardness. Both the thermal expansion coefficient and the thermal diffusivity of the former Cu-doped alloy are significantly larger than those of the latter Al-doped alloy. Although the temperature dependence of thermal diffusivity is similar for both HEAs, it is peculiar that the thermal expansion curve of the NiFeCoCrAl alloy exhibits an inflexion at temperatures of 860–912 K.

Application of a Resistive Superconducting Fault Current Limiter in a Distribution Grid

This article presents a study on short-circuit current limiting using resistive superconducting fault current limiters, based on a melt cast processed BSCCO-2212. The application of the resistive superconducting fault current limiter was analyzed when installed downstream of a substation, protecting a distribution feeder. The studied power system is based on a dynamic model of the IEEE 13-node test feeder considering a power system expansion scenario, including renewable power generation. As a result of the power system expansion, fault current levels tend to increase, and the resistive superconducting fault current limiter device is used for fault current mitigation. The main contribution of this article is the performance assessment of superconducting fault current limiters and its effects on power quality due to different fault locations in the system and by accounting the complexity of the power system topology. Results obtained demonstrate that the system expansion does not significantly raise fault current levels. It also demonstrated that the resistive superconducting fault current limiter has a desirable operation zone, and unwanted power interruption may occur due to its operation outside this zone.

Cooling rate-dependent microstructure and mechanical properties of AlxSi0.2CrFeCoNiCu1−x high entropy alloys

The influence of cooling rate on microstructure and mechanical properties of the AlxSi0.2CrFeCoNiCu1−x high entropy alloys (HEAs) were investigated. The alloys were prepared by arc melting (the Ix alloys) and injection casting assisted by liquid nitrogen (the Rx alloys). Both the phase structure of Ix and Rx alloys evolved from FCC to FCC + BCC dual-phase, and finally to a BCC phase with an increase in the Al content, and the microstructure transformed from columnar dendrite to equiaxed grain correspondingly. The x range of the Rx alloys with dual-phase structure is smaller than that of the Ix alloys. The Rx alloys also exhibited smaller grain size and spinodal decomposition plate than the Ix alloys. Additionally, because of the microstructure refinement and/or phase structure change, both the hardness and yield stress of Rx alloys were higher than the Ix alloys. The maximum increase rate presented when x = 0.6, and the minimum one presented when x = 0.4.

Effect of heat treatment on wear resistance of Fe–Cr–Mn–C–N high-interstitial stainless steel

High-Interstitial Fe–Cr–Mn–C–N stainless steels, CN66 (C+N=0.28+0.38wt%) and CN71 (C+N=0.27+0.44wt%), were produced in an induction melting furnace and cast in air atmosphere. The abrasive wear resistance of CN66 and CN71 was investigated as a function of heat treatment conditions, subsequent to casting. The wear rate of CN66 decreased from 0.107 to 0.095mm3/m. with a heat treatment of 1200°C solutionizing for 2h followed by water quenching, The value of Fe2p bonding energy of CN66 shifted from 708.93 to 708.53eV due to the heat treatment, and was caused by the dissolution of pearlite. The dissolution was also confirmed by microstructural analysis. The bonding energy of CrN, that formed as a result of heat treatment, is at 575.4eV (Cr2p2/3). The amount of ferrite phase in CN66 and CN71 was increased with heat treatment from 3.4% to 8.9% and 1.3% to 5.7%, respectively. The enhancement of wear resistance is due to the increased amount of ferrite phase resulting from lower nitrogen content in CN66 steel as well as the dissolution of pearlite by heat treatment. The abrasive wear resistance of type 316L stainless steel comparatively is lower than any of the experimental steel developed in this study.

Influence of Zr content on phase formation, transition and mechanical behavior of Ni-Ti-Hf-Zr high temperature shape memory alloys

Quaternary Ni-Ti-Hf-Zr high temperature shape memory alloys containing different Zr content (0–15 at.%) were prepared by arc melting and suction casting. The addition of Zr led to change in lattice parameters and monoclinic angle of B19′ martensite phase. The phase transformation temperature as well as yield strength of the alloys gradually increased with increasing the Zr content. Moreover, the alloys exhibited significant changes in phase transition and deformation behaviors. With the addition of Zr up to 7 at.%, the alloys exhibited double yielding and two-step phase transition behaviors. In contrast, alloys containing 10 and 15 at.%Zr revealed single yielding and one-step phase transition behaviors. These distinctions on phase transition and yielding behaviors of the alloys were mainly related to the structural evolution related to twinning mode in martensite phase of as-cast alloys originated from the change of lattice distortion during martensitic transformation by increasing of Zr content. Through detailed investigations on the microstructural features, thermal characteristics, mechanical properties and structural evolution on deformation of the alloys, the influence of Zr content on phase formation, phase transition and deformation behavior of Ni-Ti-Hf-Zr high temperature shape memory alloys was elucidated.

Significantly enhanced drilling ability of the orthopedic drill made of Zr-based bulk metallic glass composite

Zr-based bulk metallic glass composite (BMGC) presents superior unique properties, including high hardness, high fracture strength, high toughness, large elastic limit, excellent corrosion resistance, and was believed as a promising material for medical-tool applications. In this study, the 4 mm diameter rods of ZrCuAlAgSi-based (Zr-based) BMGC containing ex-situ Ta particles were successfully fabricated by two-step arc melting and suction casting method. These Zr-based BMGC rods was ascertained their amorphous nature by X-ray diffraction and differential scanning calorimetry analyses, and then machined into the orthopedic drill bits with 2 mm in diameter. The drilling tests of the commercial and Zr-based BMGC orthopedic drill bits were conducted by a specially designed indentation-drilling rig. The data of thrust force as a function of drilling distance between drill and porcine bone was recorded and analyzed to evaluate the drilling ability of the Zr-based BMGC made and commercial orthopedic drills, respectively. As a result, the Zr-based BMGC made drill presents 73% reduced thrust force than the commercial one, this indicates that the Zr-based BMGC made drill has less friction force and performs much better drilling ability.

Million-Fold Decrease in Polymer Moisture Permeability by a Graphene Monolayer.

Flexible, transparent, and moisture-impermeable materials are critical for packaging applications in electronic, food, and pharmaceutical industries. Here, we report that a single graphene layer embedded in a flexible polymer reduces its water vapor transmission rate (WVTR) by up to a million-fold. Large-area, transparent, graphene-embedded polymers (GEPs) with a WVTR as low as 10(-6) g m(-2) day(-1) are demonstrated. Monolayered graphene, synthesized by chemical vapor deposition, has been transferred onto the polymer substrate directly by a very simple and scalable melt casting process to fabricate the GEPs. The performances of the encapsulated organic photovoltaic (OPV) devices do not vary even after subjecting the GEPs to cyclic bending for 1000 cycles. Accelerated aging studies of working OPV devices encapsulated in the GEPs show a 50% lifetime of equivalent to 1 000 000 min, which satisfies the requirements of organic electronics.

Role of niobium and oxygen concentration on glass forming ability and crystallization behavior of Zr-Ni-Al-Cu-Nb bulk metallic glasses with low copper concentration

Arc melting and suction casting was used to prepare (Zr57Ni20Al15Cu8)100−xNbx bulk metallic glass alloys with Nb concentration ranging from 1.9 to 4.3at.%. The glass forming ability and crystallization behavior of these alloys were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). By varying the Nb concentration, a high glass forming range between 2 and 4at.% Nb was observed in XRD and SEM. It was also revealed that oxygen has a detrimental effect on the GFA within this high glass forming range and the severity was closely linked to the state in which oxygen was present. Since thermal activation is an intrinsic property of crystallization, the activation energy for crystallization was computed from Kissinger, Ozawa and Cheng's methods based on non-isothermal DSC data. A comparison of activation energy models revealed that Kissinger and Ozawa show similar trends while Cheng's method depicted varied results for samples containing pre-existing crystals. For amorphous samples, Kissinger and Ozawa showed the highest value of activation energy (316kJ/mol and 329kJ/mol, respectively) at 2.7at.% Nb, which is consistent with the supercooled liquid region and resulting in higher glass forming ability at this composition.