Molten Alloy Research Articles

Optimized cerium addition for microstructure and mechanical properties of SAC305

PurposeThis paper aims to analyze the effect of cerium addition on the microstructure and the mechanical properties of Tin-Silver-Copper (SAC) alloy. The mechanical properties and refined microstructure of a solder joint are vital for the reliability and performance of electronics. SAC305 alloys are potential choices to use as lead-free solders because of their good properties as compared to the conventional Tin-Lead solder alloys. However, the presence of bulk intermetallic compounds (IMCs) in the microstructure of SAC305 alloys affects their overall performance. Therefore, addition of cerium restrains the growth of IMCs and refines the microstructure, hence improving the mechanical performance.Design/methodology/approachSAC305 alloy is doped with various composition of xCerium (x = 0.15, 0.35, 0.55, 0.75, 0.95) % by weight. Pure elements in powdered form were melted in the presence of argon with periodic stirring to ensure a uniform melted alloy. The molten alloy is then poured into a pre-heated die to obtain a tensile specimen. The yield strength and universal tensile strength were determined using a fixed strain rate of 10 mm per minute or 0.1667 mm s^(−1). The IMCs are identified using X-ray diffraction, whereas the elemental phase composition and microstructure evolution are, respectively, examined by using electron dispersive spectroscopy and scanning electron microscopy.FindingsImprovement in the microstructure and mechanical properties is observed with 0.15% of cerium additions. The tensile test also showed that SAC305-0.15% cerium exhibits more stress-bearing capacity than other compositions. The 0.75% cerium doped alloy indicated some improvement because of a decrease in fracture dislocation regions, but microstructure refinement and the arrangement of IMCs are not those of 0.15% Ce. Different phases of Cu_6 Sn_5, Ag_3 Sn and CeSn_3 and ß-Sn are identified. Therefore, the addition of cerium in lower concentrations and presence of Ce-Sn IMCs improved the grain boundary structure and resulted refinement in the microstructure of the alloy, as well as an enhancement in the mechanical properties.Originality/valueCharacterization of microstructure and evaluation of mechanical properties are carried out to investigate the different composition of SAC305-xCerium alloys. Finally, an optimized cerium composition is selected for solder joint in electronics.

Chemical composition analysis on industrial scale ingots and castings of TiAl alloys

The chemical composition variation of the TiAl-4722 alloys was examined in a batch of the industrial scale master ingots, and in the corresponding castings prepared by conventional vacuum arc remelting (VAR) combined with induction skull melting (ISM) and investment casting processes. The content changes of major elements and interstitial elements were evaluated based on the chemical analysis at the top and bottom of the ingots and castings. Results show that the contents of C, N, H, Fe and Si have almost no change in the ingots and castings, suggesting that the chemical analysis on these elements can be based on the batch analysis. The O content keeps almost the same in different ingots, but exhibits relatively large differences in castings, which was probably influenced by the reaction between the shell mold and the molten alloy, and the spalling of face coat of the shell mold during casting. For the major elements of Al, Nb and Cr, the composition difference between the top and the bottom of the ingots is less than that of the castings. But for the O element, the trend is different, especially for the castings, suggesting that the investment casting is a homogenization process for Cr and Nb, but a differentiation process for O. The contents of major elements in castings fluctuate mainly in the same range as that in the ingots, indicating that the contents of the major elements are controllable during investment casting.

Producing non-dendritic A356 and A380 feedstocks: Evaluation of the effects of cooling slope casting parameters

Abstract In this study, low superheat casting and cooling slope casting processes were carried out with A356 and A380 aluminum alloys in order to obtain feedstocks with near globular microstructures. Castings were conducted at 20 °C above of the liquidus temperature for both processes and molten alloys were cast through a copper cooling slope with two different lengths (350 mm and 650 mm) and two different tilt angles (30° and 60°). In order to evaluate the significance of boron nitride coating on cooling slope, castings in short slope were carried out under both coated and uncoated conditions. Microstructural examinations and hardness measurements were carried out. According to obtained results, cooling slope casting caused superior microstructural properties as compared to low superheat casting, especially for A356 alloy. 30° tilt angle was found more efficient in order to obtain a more globular microstructure for A356, while, on the other hand, the tilt angle of 60° was detected more favorable in that manner for A380. Obtained grain size measurements were slightly improved with the employment of short slope and coating was found beneficial especially for A356 alloy. The measured hardness values did not display any significant difference in the same alloy type except in the low superheat cast A356 specimen, which was obtained with coarser microstructure.

The effects of aging on the cyclical thermal shock response of a copper-beryllium alloy as a substrate of cooling wheel in planar flow casting process

In planar flow casting (PFC) process, the molten alloy from nozzle exerts cyclical thermal shock on the substrate surface of cooling wheel and the cyclical thermal shock causes damage to the substrate surface in the form of defects. In this paper, a 2D numerical model was explored and the cyclical thermal shock on the surface of cooling wheel was simulated by numerical method using practical casting parameters. A batch of hot rolled copper-beryllium (Cu-2Be) cylindrical rings was prepared and subjected to solution annealing and aging treatments. The coefficients of thermal conductivity, thermal expansion coefficients and mechanical properties of Cu-2Be rings with different aging conditions were measured. The metallograph and SEM of the Cu-2Be rings subjected to 105 cycles of thermal shock were examined. The simulation results show that the surface temperature underneath the puddle is heated up drastically to a maximum temperature around 350 °C and cooled down to a minimum temperature around 140 °C in each revolution in quasi-steady process, and the lower thermal conductivity leads to the higher surface temperature for Cu-2Be substrate. The mechanical and physical responses of a Cu-2Be alloy aged at different conditions as a substrate of cooling wheel have been investigated after 105 cycles of thermal shock in practical casting. It was observed that the cyclical thermal shock leads to damage to Cu-2Be surface which affects the surface quality of as-cast ribbon. It was found that higher thermal expansion coefficient of Cu-2Be alloy leads to large magnitude of surface expansion and surface shrinkage which results in crack damage while lower thermal expansion coefficient of Cu-2Be alloy resulting from higher temperature aging is benefit to reducing the magnitude of surface expansion and surface shrinkage but the strength of Cu-2Be substrate is also reduced and intergranular erosion occurs after 105 cycles of thermal shock.

Producing non-dendritic A356 and A380 feedstocks: Evaluation of the effects of cooling slope casting parameters

Abstract In this study, low superheat casting and cooling slope casting processes were carried out with A356 and A380 aluminum alloys in order to obtain feedstocks with near globular microstructures. Castings were conducted at 20 °C above of the liquidus temperature for both processes and molten alloys were cast through a copper cooling slope with two different lengths (350 mm and 650 mm) and two different tilt angles (30° and 60°). In order to evaluate the significance of boron nitride coating on cooling slope, castings in short slope were carried out under both coated and uncoated conditions. Microstructural examinations and hardness measurements were carried out. According to obtained results, cooling slope casting caused superior microstructural properties as compared to low superheat casting, especially for A356 alloy. 30° tilt angle was found more efficient in order to obtain a more globular microstructure for A356, while, on the other hand, the tilt angle of 60° was detected more favorable in that manner for A380. Obtained grain size measurements were slightly improved with the employment of short slope and coating was found beneficial especially for A356 alloy. The measured hardness values did not display any significant difference in the same alloy type except in the low superheat cast A356 specimen, which was obtained with coarser microstructure.

Fabrication of Powders of Alloy 25Kh15KA for Synthesizing Permanent Magnets by Selective Laser Melting

The possibility of fabrication of powders from alloy 25Kh15KA for synthesizing permanent magnets by the method of selective laser melting is considered. The method is used to make specimens of permanent magnets 10 × 10 × 9 mm size with a density meeting the State Standard for 25Kh15KA magnets produced by the standard metallurgical process to obtain a coercivity of 45.4 kAm, a residual induction of 1.02 T and a maximum magnetic energy 24 kJm3 . It is shown that the morphology of the particles and the granulometric composition of the powders fabricated by gas atomizing are better than those of the mixtures of elementary Fe, Cr and Co powders and of the powders produced by centrifugal sputtering of molten alloy 25Kh15KA from a scull-melting crucible rotated at controlled speed.

Effects of Casting Conditions for Reduced Pressure Test on Melt Quality of Al-Si Alloy

The present study investigated the effect of the casting conditions for the reduced pressure test (RPT) on the melt quality of Al-Si alloy. The casting conditions considered in RPT were the atmospheric exposure during melting, sampling method, and mold pre-heating temperature. Density Index (DI) was measured to quantify the melt quality of the Al-Si alloy casted with the different casting conditions for the RPT. The sample with blocking atmospheric exposure during melting was 5.6% lower in DI than the one without blocking. DI showed a 1.9% gap between scooping-out and pouring sampling methods. Increasing mold pre-heating temperature from 100 °C to 250 °C increased the DI of the alloy from 8.5% to 18.7%. On the other hand, when the mold pre-heating temperature was 350 °C, the DI of the alloy dropped sharply to 0.9%. The melt quality of the alloys was analyzed by measuring the pores and microstructure and simulating the solidification of the samples. It was presumed that the oxides and inclusions in the molten alloys caused the difference in DI according to the atmospheric exposure and the sampling method. The difference in DI according to the mold pre-heating temperature could be understood by calculating the solidification starting time and hydrogen diffusion coefficient during the solidification of the alloys in RPT.

Effect of Si Addition on Flow Behavior in Al-Mg and Al-Mg-Si Molten Alloys

This study investigates the fluidity change of Al-Mg binary alloys with the addition of Si and examines the factors that determine flow length in these binary and ternary alloys. Fluidity tests for Al-6Mg-xSi (all compositions in mass percent; x = 0, 3, 5, or 7) alloys were carried out using a spiral-type steel mold. The results show a decrease in both the rate of oxidation and the freezing range, as well as an increase in the heat of fusion of Al-Mg-Si ternary alloys with increasing Si content. Nevertheless, at constant superheating of 60 °C, a lower fluidity was achieved in ternary alloys of ≤ 5 pct Si content than in Al-6Mg alloy. However, further increase to 7 pct Si content yielded a flow length 25 pct higher than for Al-6Mg alloy. Further superheating above the liquidus temperature resulted in increased flow length for Al-Mg-Si ternary alloys, with a flow length increase of about 1 cm per 5 °C temperature increase. Instead of solidification range, Tα–Te range (the temperature difference between the start of the pro-eutectic α-Al phase (Tα) and eutectic phases (Te)), was used in this study, as it was found to be a more suitable criterion for predicting flow length for Al-Mg-Si ternary alloys. The key variables for predicting flow length were found to differ based on alloy composition. In the ternary alloys, total heat content and (Tα–Te) range were found to be the most influential factors driving flow behavior, while the poor fluidity of Al-6Mg binary alloys was found to be driven primarily by high oxidation tendency and low latent heat of fusion.

Influence of Manufacturing Conditions on Inclusion Characteristics and Mechanical Properties of FeCrNiMnCo Alloy

Three CoCrFeMnNi high-entropy alloys (HEAs) were produced by vacuum induction melting, induction melting under inert gas atmosphere, and melting under inert gas atmosphere followed by air exposure, respectively. The different manufacturing conditions for the three investigated alloys resulted in different levels and types of inclusions. The alloys melted under vacuum or inert gas contained Al2O3 inclusions formed by impurity Al, due to its high oxidation tendency. The molten alloy exposed in air showed an excessive oxidation. During oxidation of the molten alloy in air, impurity Al was initially oxidized, and fine MnCr2O4 inclusions were formed rather than pure Al2O3 inclusions. This difference was analyzed based on thermodynamic calculations. Specifically, the influence of impurity content on the inclusion characteristics was investigated for the three HEAs. Moreover, the inclusion characteristics were found to have an influence on mechanical properties of the alloys also. In air-exposed HEA, smaller inclusions were formed, resulting in a higher dislocation density at the matrix/inclusion interface and thus strengthening of the HEA. Thus, it is proposed that atmospheric conditions could be an important factor to control the inclusion characteristics and to form fine inclusion particles, which could improve the mechanical properties of HEAs.

Synthesis, Characterisation and Mechanical Behaviour of In-situ Al7SiMg/TiB2 Composites Prepared by Salt-Metal Reaction

Aluminium based lightweight-high strength metal matrix composites are widely used in applications such as automotive, military, and aerospace because of their improved physical, thermal and mechanical properties. In this work, the synthesis, structural and mechanical characterisation of Al7SiMg/TiB2 composites prepared by the in-situ route was studied. The composites with different amounts (4 and 9 wt. %) of TiB2 particles were developed as a result of the reaction between the molten alloy and the K2TiF6 and KBF4 salts at 810 °C. These composites were examined by XRD and SEM/EDS. The elemental phases present in the composite and presence of TiB2 were confirmed by XRD results. SEM micrographs showed the formation and distribution of micron-sized TiB2 particles mostly along the grain boundary of the alloy matrix. The structure of TiB2 particles was hexagonal. The effect of TiB2 content on the hardness and wear resistance was investigated by using Vickers hardness tester and Pin-on Disc apparatus at room temperature. Increased hardness indicated increased wt. % of TiB2 particles in the composites. The wear data indicated the amount of TiB2 particles influence wear rate and mass loss values, while wear rate and mass loss of material increase with applied normal load and sliding distance.

Effects of Mold Materials on the Interfacial Reaction between Magnesium Alloy and Ceramic Shell Mold during Investment Casting

In order to suppress the interfacial reaction between the ceramic shell mold and the magnesium molten alloy during the investment casting process, a mold material with a high thermodynamic stability based on alkaline zirconium sol (CH4NO3Zr) binder and corundum (Al2O3) powder was prepared. The effects of the mold materials and casting thicknesses on the interfacial reaction were investigated by an optical microscope, X-ray diffraction, a scanning electron microscope, and an energy dispersive spectroscope analysis. The results suggested that the casting poured by the conventional ZrSiO4 mold has a serious reaction on the surface, and the reaction was more severe when the casting thickness was increased. The oxidation layer was approximately 300 μm in some severe areas of 45 mm thickness. The XRD and EDS results showed that the reaction interface mainly contains MgO and Mg2Si. While the casting poured by the Al2O3 mold provides a light and smooth surface, the reaction layer was only 1.5 μm on average. The reaction interface mainly contains MgO and Mg2F.

Smartdust 3D-Printed Graphene-Based Al/Ga Robots for Photocatalytic Degradation of Explosives.

Milli/micro/nanorobots are considered smart devices able to convert energy taken from different sources into mechanical movement and accomplish the appointed tasks. Future advances and realization of these tiny devices are mostly limited by the narrow window of material choices, the fuel requirement, multistep surface functionalization, rational structural design, and propulsion ability in complex environments. All these aspects call for intensive improvements that may speed up the real application of such miniaturized robots. 3D-printed graphene-based smartdust robots provided with a magnetic response and filled with aluminum/gallium molten alloy (Al/Ga) for autonomous motion are presented. These robots can swim by reacting with the surrounding environment without adding any fuel. Because their outer surface is coated with a hydrogel/photocatalyst (chitosan/carbon nitride, C3 N4 ) layer, these robots are used for the photocatalytic degradation of the picric acid as an explosive model molecule under visible light. The results show a fast and efficient degradation of picric acid that is attributed to a synergistic effect between the adsorption capability of the chitosan and the photocatalytic activity of C3 N4 particles. This work provides added insight into the large-scale fabrication, easy functionalization, and propulsion of tiny robots for environmental applications.

Draining under gravity in steel galvanization.

The problem of the coating of steel has been considered in several Mathematics in Industry study groups. In this process, after passing through a bath of molten alloy, steel sheeting is drawn upward to allow draining under gravity and stripping using an air knife, leaving a coating of desirable thickness. Here we discuss some aspects of the problem and in particular the gravity draining component. The problem is a very nice introduction to industrial modelling for students, but is also relevant for manufacturing.

Anode Properties of Silicide/Si Composite Alloy Electrodes Prepared By Rapid Quenching for Lithium-Ion Battery

1. Introduction Si is attractive as an anode active material for lithium ion battery (LIB) due to its high theoretical capacity. However, large volume expansion and contraction of Si occur during charge and discharge reactions, respectively, which results in pulverization after cycling. Therefore, Si electrode shows poor cyclability. On the other hand, composite electrodes consisting of transition metal silicide and Si exhibit advanced cycling performance compared to Si-alone electrode. We have reported that the following four properties are required for silicide phase: (1) mechanical properties suitable for relaxation of the stress from Si, (2) high electronic conductivity, (3) moderate reactivity with Li+, and (4) high thermodynamic stability[1-5].Rapid quenching is one of the preparing methods of silicide/Si composite alloy. In this study, we focused that this method can control positional relation between Si and silicide phase by changing additives or its amounts. We prepared various Si-alloys and investigated relationship between their anode properties and the arrangement.1. Experiment Si-Fe and Si-Zr alloy were prepared by rapid quenching. First, ingot of Si-alloy was melted at 1500 oC by induction furnace. After melting, molten alloy was dropped on Cu roll at rotating speed of 40 m/s. Thus, molten alloy was quenched and Si-alloy (silicide/Si composite) ribbons were prepared. The ratio of Si phase to silicide phase was set to be 33 : 67 mass% (ideal discharge capacity of Si-alloy : 1200 mA h g-1). LIB anode properties of Si-alloy electrodes were investigated using slurry electrode consisting of 80 wt.% active material, 5 wt.% ketjen black, and 15 wt.% polyamic-acid. The slurry was spread out onto SUS316L foil with a thickness of 20 mm and a loading amount of about 30 mg cm-2, and then dried at 70oC to obtain a working electrode. A 2032 type coin cell was comprised the working electrode, a separator of glass fiber filter, and a counter electrode of Li metal sheet (thickness: 1 mm, diameter: 12 mm). 1M LiPF6 dissolved in ethylene carbonate (EC) : diethyl carbonate (DEC) (1 : 1 vol.%) was employed as an electrolyte.The charge-discharge testing was performed at 25oC and the current density of 0.07 A g-1 (0.05C), during the first cycle, and 0.3 A g-1 (0.2C) during subsequent cycles in the potential range of 0.002–1.0 V vs. Li/Li+.1. Results and discussions Fig. 1 shows the field emission-electron probe micro analysis (FE-EPMA) results of cross-section of Si-Fe alloy and Si-Zr alloy ribbons prepared by rapid quenching method. In Fig. 1(a), white areas were located around black areas. Corresponding element mapping revealed that black and white areas represent Si and FeSi2 phases, respectively. Therefore, the results indicate that silicide phase surrounds Si phase in Si-Fe alloy. On the other hand, ZrSi2 phase surrounded Si phase in Fig. 1(b). Thus, we could prepare various Si-alloys having different positional relation between Si and silicide phases by changing additive elements.Fig. 2 shows cycling performance of Si-alloy electrodes in 1 M LiPF6/EC:DEC(1:1 vol.%). Si-Zr alloy electrode exhibited higher capacity than Si-Fe alloy. In addition, cycle stability of Si-Zr alloy was almost the same as that of Si-Fe alloy in spite of high capacity. Fig. 3 shows the cross-sectional scanning electron microscope (SEM) images of Si-alloy electrodes before and after the 50th cycle. In Si-Fe alloy, particles of Si-Fe alloy were collapsed after the cycling and the electrode thickness significantly increased after the 50th cycle. On the other hand, particle shape of Si-Zr alloy was maintained after the 50th cycle and change in the thickness was much smaller than Si-Fe alloy.These results indicate that positional relation between Si and silicide phases influences on collapse behavior of Si-alloy during charge-discharge and the collapse of Si-alloy can be suppressed by Si phase surrounding silicide phase like Si-Zr alloy.

Modelling of intermetallic layers formation during solid-liquid joining of dissimilar metallic materials

Joining of dissimilar metallic materials gives rise to the production of components with improved properties. At the joint interface, the formation of brittle intermetallic layers might deteriorate the component application. Therefore, its formation and growth must be well understood and carefully controlled. Numerical simulations assist in the determination of processes parameters to obtain the desired bond characteristics. In solid-liquid joining processes, the melt movement plays an important role und must be accounted in the simulations. In this paper, a mathematical model at the continuum scale is used for the description of the interface formation during solid-liquid joining. The description of convection and advection of the molten alloy and the dissolution of the solid substrate are of interest. The substrate dissolution into the melt alters the local composition of the molten alloy, leading to precipitation of intermetallic compounds on the substrate surface during the solidification process. To account for these phenomena, convection heat transfer with phase transformation and diffusion and reaction at the solid-liquid interface are considered in the mathematical model that is based on conservation equations of mass, momentum, energy and species. The different scale problem is solved by applying a dynamic mesh refinement at the interface to accurately solve the intermetallic layer growth. The model was implemented in OpenFoam® and simulation results for the intermetallic layer thickness as a function of solid substrate temperature (Ts) for compound casting between initially liquid Al and a solid Cu substrate are presented. In general, for Ts initial value ranging from 400 to 700 °C while keeping the initial Al melt temperate at 750 °C, the intermetallic layers thickness increases as Ts increases.

In-situ synthesis, microstructure and mechanism of SiC/Al–Mg–Si composites: Effects of Mg addition

The SiC/Al–Mg–Si composite was obtained by in-situ synthesis, and the effects of Mg addition were investigated in this process. Mechanism of in situ SiC growth in the Resin–Al–Mg–Si system was investigated by fabricating and characterizing a SiC/Al–Mg–Si composite under moderate conditions. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to analyze the phase and its microstructure, with the aim of investigating the evolvement of grains in the alloy matrix. Mg2Si formed under higher Mg added conditions, which decreased the molten liquid and Si solute concentrations. Tiny amounts of MgO and MgAl2O4 proved that the pyrolysis gas of resin reacts slightly with the matrix. The key conditions of in-situ synthesis SiC were found that the Mg addition and the Si concentration in the molten alloy were 3%–5% and over 17. 27 % respectively. Ostwald ripening was used to explain the decrease in tiny SiC grains at elevated temperatures. In situ SiC growth is controlled by the interfacial reaction-diffusion mixed model through two different routes in the molten alloy. Two modes of in-situ synthesis were suggested. The intermediate product and template for in situ SiC growth are Al4C3, and Si was shown to diffuse into its particles gradually. Flowing Si in molten alloy reacted with pyrolysis C directly. Specimens validated the peak bending strength with a rise in temperature. The maximal bending strength was 251.89 MPa.

Fluid Dynamics Effects on Microstructure Prediction in Single-Laser Tracks for Additive Manufacturing of IN625

Single-track laser fusion were simulated using a heat-transfer-solidification-only (HTS) model and its extension with fluid dynamics (HTS_FD) model using a parallel open-source code, which included laminar fluid dynamics, flat-free surface of the molten alloy, heat transfer, phase-change, evaporation, and surface tension phenomena. The results illustrate that the fluid dynamics affects the solidification and ensuing microstructure. For the HTS_FD simulations, thermal gradient, G was found to exhibit a maximum at the extremity of the solidified pool (i.e., at the free surface), while for HTS simulations, G exhibited a maximum around the entire edge of the solidified pool. HTS_FD simulations predicted a wider range of cooling rates than the HTS simulations, exhibited an increased spread in the solidification speed, V variation within the melt-pool with respect to the HTS model results. Primary dendrite arm spacing (PDAS) were evaluated based on power law correlations and marginal stability theory models using the (G, V) from HTS and HTS_FD simulations to quantify the effect of the fluid dynamics on the microstructure. At low-laser powers and low-scan speeds, the PDAS obtained with the fluid dynamics model (HTS_FD) was larger by more than 30 pct with respect to the PDAS calculated with the simple HTS model. A new PDAS correlation, i.e., lambda_{1} left[ {mu {text{m}}} right] = 832;Gleft[ {text{K/m}} right]^{ - 0.5} Vleft[ {text{m/s}} right]^{ - 0.25} , which uses the (G, V) results from the HTS_FD model was developed and validated against experimental results.

Measuring hand-pouring motion in casting process using augmented reality marker tracking

Elucidations of workers’ pouring motions and the resultant inflow behavior of molten alloy into the mold are important because the inflow behavior is well known to affect casting quality. Nevertheless, few reports in the relevant literature describe studies of inflow behavior effects on casting quality because of difficulty in measuring the worker’s pouring motion. Therefore, this study was conducted to examine worker’s pouring motions in the actual casting field and to describe the relation between the motion and casting defects. For that, an augmented reality (AR) marker-tracking method was used to conduct contactless measurements of the pouring motion. Validation of the method revealed that the error was less than 0.9° during roll motion from 0° to 90°. Subsequently, measurements of worker’s pouring motions were conducted during actual aluminum alloy casting. Results demonstrated that the method enabled the continuous acquisition of the translation (x, y, and z) and rotation (roll, pitch, and yaw) of the crucible during pouring with a usual pouring device and crucible. Finally, the AR marker-tracking method was capable of revealing the difference of the worker’s pouring motions corresponding to the occurrence or non-occurrence of a misrun defect during the gravity die casting. The obtained results demonstrated that the AR marker-tracking method can be used to measure the worker’s pouring motion. It can reveal relations between its motion and the casting defect.

Effect of in-situ crystalline phases on the mechanical properties and energy release behaviors of Zr55Ni5Al10Cu30 bulk metallic glasses

To explore the application potential of bulk metallic glasses (BMGs) as energetic structural materials (ESMs) and address the limitations in the preparation of large-sized monolithic BMGs, the effect of the in-situ crystalline phases on the mechanical properties and energy release behaviors of Zr55Ni5Al10Cu30 BMGs are evaluated. The results indicate that while the content of in-situ crystalline phases in Zr55Ni5Al10Cu30 alloy are effectively tailored by controlling the cooling rate of molten alloys, the mechanical properties and energy release behaviors of Zr55Ni5Al10Cu30 are determined by the content of in-situ crystalline phases. The alloy prepared using the highest cooling rate possesses the lowest crystalline phase content as well as the highest strength and deformability. By contrast, the complete crystalline alloy prepared by annealing exhibits the highest energy release characteristics under high-speed impact owing to the highest degree of brittleness and most oxidation reaction. The Zr55Ni5Al10Cu30 alloy with different crystalline phase content shows potential as an ESM. Its mechanical properties and energetic characteristics can be effectively tailored by controlling the content of in-situ crystalline phases via cooling rate modulation.

Estimation of time-dependent heat transfer coefficient in unidirectional casting using a numerical model coupled with solidification analysis and data assimilation

We have recently developed a method to estimate the heat transfer coefficient based on data assimilation. To understand its usefulness for estimating the time-dependent heat transfer coefficient, herein we performed unidirectional casting experiments of Al-1mass%Si alloy and obtained the cooling curves during solidification. The experimental data were then used to validate the estimated time-dependent heat transfer coefficient. Consequently, the measured cooling curves could be accurately simulated, and the average errors between measured and simulated cooling curves were below 0.8%. The estimated time-dependent heat transfer coefficient was 29461.5 Wm−2K−1 at the initial stage of cooling, which rapidly decreased to about 6000 Wm−2K−1 and then gradually decreased to about 1000 Wm−2K−1. These values are reasonable as the heat transfer coefficients for castings of Al base alloys. Additionally, the effect of the setting parameters of the data assimilation were evaluated. It was found that the position of the cooling curve(s) used in the estimation was the most important factor and a cooling curve measured at the position near the surface of the mold should be utilized. This method allows the reasonable estimation of the time-dependent heat transfer coefficient between the mold and molten alloy for unidirectional castings without using trial and error, and experimentally measured cooling curves can be accurately reproduced by solidification analysis.