Semi-solid Slurry Research Articles

Interfacial bonding mechanism of graphene nanoplatelets reinforced AZ91D magnesium alloy prepared by semi-solid injection molding

The incompatibility between the strength and thermal conductivity of magnesium alloys limits their application in heat dissipation components. Magnesium matrix composites were obtained by adding reinforcements into the AZ91D alloy to achieve synergistic enhancement of mechanical and thermal conductivity to promote the application of magnesium alloy. Graphene nanoplatelets (GNPs) reinforced magnesium matrix composites were successfully prepared by semi-solid injection molding. The high viscosity of the semi-solid metal slurry contributes to the homogeneous dispersion of GNPs in the magnesium matrix. A GNPs/MgO/Mg heterostructure with high interfacial bonding strength was found at the interface of GNPs and α-Mg matrix. The semi-solid casting method improves the mechanical properties of the composites by grain refinement and simultaneously reduces the thermal conductivity. The addition of GNPs can balance the mechanical and thermal conductivity enhancement, and the most balanced properties of the composites are obtained when the content of GNPs is 0.3 wt%, with a tensile strength of 243.1 MPa, Vickers hardness of 93.7 HV, and thermal conductivity of 74.8 W/(m·K). Therefore, the semi-solid forming method is considered a promising processing method, and GNPs is considered an ideal reinforcement material to improve the performance of the magnesium matrix.

Design and Optimization of 3D-Printed Tablets Containing Mucuna Extracts for Erectile Dysfunction Management: A DoE-Guided Study.

Erectile dysfunction (ED) refers to the inability of the penis to maintain a firm erection during sexual activity. Mucuna, or M. pruriens, contains levodopa, a compound showing promise in ED treatment. However, formulating Mucuna extract into tablet dosage forms is challenging due to its semisolid nature. This study aimed to develop sustained-release tablets containing Mucuna extract via semisolid extrusion 3D printing. Eudragit RS PO (Eudragit) served as a sustained-release polymer, with poly (vinyl alcohol) (PVA) as a co-polymer for forming the tablet matrices. This study had the following two main phases: screening, which identified the factors affecting the printability, and optimization, which focused on the factors influencing the levodopa release and its consistency. The results showed that both the polymeric solid percentage content (PSPC) in the semisolid slurry and the Eudragit-PVA ratio significantly affected the printability. All of the formulations were printable, and the PSPC and Eudragit-PVA ratios were incorporated into the optimized model. The desired formulation, achieving targeted levodopa release and consistency, had a PSPC of 58.8% and a Eudragit-PVA ratio of 2.87:1. In conclusion, semisolid extrusion 3D printing guided by the design of experiments (DoE) proved feasible for producing reliable 3D-printed tablets with consistent active ingredients and desired release rates.

Multi-physics coupled numerical simulation study to optimize process parameters for electromagnetic stirring of semi-solid A356 aluminum alloy under the influence of skin effect

The electromagnetic stirring (EMS) method stands as a widely used technique in creating semi-solid aluminum alloy slurry due to its convenience and precision in parameter control compared to other methods. In this study, a comprehensive model that combines electromagnetics, flow, heat transfer and solidification was formed. By analyzing the influence of input current and frequency on the electromagnetic force, the behavior of various process parameters in velocity field and temperature field under influence of the skin effect is investigated. The aim is to find the optimal process parameters for production of slurry using the low-frequency EMS. The results show that within the investigated range, by adjusting the input current and frequency to 150 A and 15 Hz, higher fluid velocities and appropriate distribution of vortex zones can be observed, while achieving a uniform temperature field, the highest cooling rate and the minimum radial temperature difference. In addition, the sample prepared under the optimal process parameters shows that the melt edge is least affected by the skin effect, which leads to a higher stirring strength and a smaller overall grain size, which is consistent with the theoretical skin effect research found within the simulation section.

Influence of solute content and cooling rate on the preparation of semi-solid slurries for novel creep-resistant Mg-Gd-Ca-Zr alloys

The semi-solid Mg-Gd-Ca-Zr alloys slurries with fine and spherical α-Mg particles were successfully prepared. The influence of solute Gd and Zr contents, and cooling rate on the morphological evolution of α-Mg are systematically investigated. The results showed that addition of Zr will turn the coarse dendritic α-Mg particles into fine and globular particles. With the increase of Zr addition from 0 to 0.6 wt%, the particle size decreases, and the particle density and shape factor increase continuously. With the change of solute Gd content from 5 to 15 wt% in the Mg-yGd-2Ca-0.6Zr alloy, the particle size of α-Mg particles decreases continuously, and shape factor increases continuously. With cooling rate decreases from 3 to 1.5 °C/min, the α-Mg particles are slightly coarsened and the morphology are kept nearly globular, while with further decreasing into 0.5 °C/min, the α-Mg particles are severely coarsened and turned into irregular shape. The optimal Zr addition is ∼0.6 wt% and Gd addition is no less than 10 wt%, and the optimal cooling rate is 1.5–3 °C/min. The mechanisms for obtaining fine and spherical α-Mg particles through Zr and Gd additions are discussed to be different roles of heterogenous nucleation effects and growth restriction effects.

A novel atomistic approach of estimating interfacial free energy and growth kinetics of primary Mg2Si during semi solid slurry formation of the novel Al–15Mg2Si–4.5Si composite

A novel atomistic approach of estimating interfacial free energy and growth kinetics of primary Mg2Si during semi solid slurry formation of the novel Al–15Mg2Si–4.5Si composite

Entrained Defects in A356 Semisolid Slurry Produced by RSF and CSC Processes

Entrained Defects in A356 Semisolid Slurry Produced by RSF and CSC Processes

Semi-Solid Slurries for Rheocasting of Hypoeutectic Al-Si-X Alloys Produced by Self-Stirring in Serpentine Channels

Nowadays it is common to see the production of complex and critical automotive and aeronautical components reduced in weight for energy efficiency using light alloys with improved microstructural and mechanical properties. The casting processes involved in this trend are strong; in this study, an optimized design of a vertical serpentine channel and a novel design of a horizontal serpentine channel to produce semi-solid slurry (S2S) with thixotropic behavior by self-stirring for rheocasting of A380 and A356 alloys are tested. Simultaneously, chilling during solidification, flow development, and shearing on the alloys to improve the performance of solid fractions and self-stirring at high shear rate are applied. The effects of these conditions on the modification of the morphology transition of the α(Al) phase from dendrite to equiaxed grain are discussed. The results suggest the ability of the mentioned processes to promote the morphological transition of the primary solid due to the produced equiaxed grains of α(Al) phase having sizes between 25–50 µm from A380 alloy processed by vertical self-stirring. On the other hand, the treatment of the A356 alloy using the new horizontal serpentine channel produces equiaxed grains with an average size of 39 µm. Unexpected Si crystals, trapped in the α(Al) phase using both methods with both alloys, are detected. The applied operation parameters were aided by gravity-pouring close to the liquidus temperature, and the obtained microstructural results show the ability for S2S to form alongside thixotropic behavior and non-dendritic solidification by mean of self-stirring in the serpentine channels, suggesting the potential for further experiments under die-casting conditions.

Rheological Characterization of a Thixotropic Semisolid Slurry by Means of Numerical Simulations of Squeeze-Flow Experiments

We propose a methodology for the rheological characterization of a semisolid metal slurry using experimental squeeze-flow data. The slurry is modeled as a structural thixotropic viscoplastic material, obeying the regularized Herschel–Bulkley constitutive equation. All rheological parameters are assumed to vary with the structure parameter that is governed by first-order kinetics accounting for the material structure breakdown and build-up. The squeeze flow is simulated using finite elements in a Lagrangian framework. The evolution of the sample height has been studied for wide ranges of the Bingham and Reynolds numbers, the power-law exponent as well as the kinetics parameters of the structure parameter. Systematic comparisons have been carried out with available experimental data on a semisolid aluminum alloy (A356), where the sample is compressed from its top side under a specified strain of 80% at a temperature of 582 °C, while the bottom side remains fixed. Excellent agreement with the experimental data could be achieved provided that at the initial instances (up to 0.01 s) of the experiment, the applied load is much higher than the nominal experimental load and that the yield stress and the power-law exponent vary linearly with the structure parameter. The first assumption implies that a different model, such as an elastoviscoplastic one, needs to be employed during the initial stages of the experiment. As for the second one, the evolution of the sample height can be reproduced allowing the yield stress to vary from 0 (no structure) to a maximum nominal value (full structure) and the power-law exponent from 0.2 to 1.4, i.e., from the shear-thinning to the shear-thickening regime. These variations are consistent with the internal microstructure variation pattern known to be exhibited by semisolid slurries.

JIS ADC12 Aluminum Alloy Semi-Solid Slurry Preparation Technology by Applying Mechanical Vibration

JIS ADC12 Aluminum Alloy Semi-Solid Slurry Preparation Technology by Applying Mechanical Vibration

Elucidating in-situ heat generation of LiFePO4 semi-solid lithium slurry battery under specific cycling protocols

Semi-solid lithium slurry battery combines the advantages of the high energy density of lithium-ion battery and the flowability of flow battery electrodes and has attracted attention in energy storage. Elucidating the heat generation during cycling is crucial for evaluating the safety. However, there is a relative lack of research in this field of semi-solid lithium slurry battery. Herein, the heat generation of lithium iron phosphate (LiFePO4) semi-solid lithium slurry battery during cycling under specific cycling protocols is investigated in this work. The results show that the battery has lower heat generation when cycling at an ambient temperature of 35–50 ℃ and a charging cutoff voltage below 4.0 V, meanwhile, it maintains considerable capacity. However, when the charging cutoff voltage exceeds 4.4 V, the cyclic heat generation of the battery increases significantly, and the capacity attenuates significantly. Meanwhile, the classical equation for calculating battery heat generation of lithium-ion battery is no longer reliable. This is mainly because the electrolyte content of the semi-solid lithium slurry battery is too high (over 80 %), and at high charging cutoff voltage, the side decomposition reactions of the electrolyte increase significantly. Subsequent characterization of electrode materials also confirms this inference. This study can provide a clearer understanding of the safety of semi-solid lithium slurry battery and has guiding implications for industrial applications.

Investigation on the effects of isothermal holding temperature and time on the coarsening mechanism and rheological properties of ADC12 Al semi-solid slurry

The current work's key emphasis is on investigating the influence of isothermal holding temperature and time on the microstructural development and coarsening rate during the directly generated semi-solid slurry of ADC12 Al alloy from the cooling slope process. Additionally, a thorough investigation is conducted to optimize process variables in the rheo-pressure die-casting process to determine the correlation between the non-Newtonian flow behaviour and its morphological characteristics of the quenched slurry of ADC12 Al alloy. The obtained results inferred that with increasing isothermal holding time, average grain size marginally increases initially, then significantly increases with increasing time, while shape factor increases first and then declines. Furthermore, when isothermal temperatures increase, the average grain size rises, while the shape factor rises first before decreasing. As a result of the increase in grain size due to elevated processing temperature and prolonged processing time, the aluminium alloy's hardness deteriorated. The ideal condition for more spheroidization of α-Al in the synthesized semi-solid slurry of ADC12 aluminium alloys was at an isothermal temperature of 565 °C and a holding time of 7 min. Under ideal processing conditions, the alloy's grain size, shape factor, and hardness were 31 μm, 0.89, and 62.32 HV, respectively. The semi-solids of ADC12 Al alloy have a low coarsening coefficient. The coarsening rate constant at 565 °C was calculated using the Lifshitz-Slyozov-Wagner relationship, and a value of 37 μm3/s was discovered. The findings of the isothermal rheology experiment demonstrate that viscosity decreases as the shear rate increases, confirming the existence of shear-thinning actions in semi-solid slurries.

Effect of flow characteristics in the inner gate on the microstructure of a semi-solid processed hypereutectic Al–Si alloy

ABSTRACTThis study aims to prepare hypereutectic Al–Si alloy cylindrical samples with hard inner surfaces by changing the depth of inner gates in squeeze casting molds. The characteristic parameters (volume fraction and equivalent diameter) of the hard phases (primary Si and Fe-rich phases) and the hardness of the samples were observed. When the depth of the inner gate is 5 mm, there is a radial gradient in the characteristic parameters of the hard phases in the members resulting in surface strengthening of the structural member. However, when the depth of the inner gate is 9 mm, there is no radial gradient. The mechanisms of achieving surface strengthening in hypereutectic Al–Si alloy cylindrical samples by changing the rheological characteristics of semi-solid Al–Si alloy slurries were revealed.

A Comparative Study on Microstructure, Segregation, and Mechanical Properties of Al-Si-Mg Alloy Parts Processed by GISS-HPDC and SEED-HPDC.

There are multiple routes to prepare semi-solid slurries with a globular microstructure for semi-solid forming. The variations in the microstructure of semi-solid slurries prepared using different routes may lead to significant differences in the flow behavior and mechanical properties of rheo-diecasting parts. Therefore, it is crucial to have a comprehensive understanding of the microstructure evolution associated with different slurry preparation routes and their resulting effects. In this study, the gas-induced semi-solid process (GISS) and the swirl enthalpy equilibrium device (SEED) routes were employed to prepare semi-solid Al-Si-Mg slurries for their simplicity and productivity in potential industrial applications. The prepared slurries were then injected into the shoot sleeves of a high-pressure die casting (HPDC) machine to produce tensile test bars. Subsequently, the bars underwent T6 treatment to enhance their mechanical properties. The microstructure, segregation, and mechanical properties of the samples were investigated and compared with those of conventional HPDC. The results indicated that the GISS and SEED can produce semi-solid slurries containing a spherical α-Al primary phase, as opposed to the dendritic structure commonly found in conventional castings. The liquid fraction had a significant effect on the flow behavior, resulting in variations in liquid segregation and mechanical properties. It was observed that a higher solid fraction (>75%) had a suppressing effect on surface liquid segregation. In addition, the tendency for liquid segregation gradually increased along the filling direction due to the special flow behavior of the semi-solid slurry with a low solid fraction. Furthermore, under the same die-casting process parameters, the conventional HPDC samples exhibit higher yield stress (139 ± 3 MPa) compared to SEED-HPDC and GISS-HPDC samples, which may be attributed to the small grain size and the distribution of eutectic phases. After undergoing the T6 treatment, both SEED-HPDC and GISS-HPDC samples showed a significant improvement in yield and tensile strength. These improvements are a result of solution and precipitation strengthening effects as well as the spheroidization of the eutectic Si phase. Moreover, the heat-treated SEED-HPDC samples demonstrate higher ultimate strength (336 ± 5 MPa) and elongation (13.7 ± 0.3%) in comparison to the GISS-HPDC samples (307 ± 4 MPa, 8.8 ± 0.2%) after heat treatment, mainly due to their low porosity density. These findings suggest that both GISS-HPDC and SEED-HPDC processes can be utilized to produce parts with favorable mechanical properties by implementing appropriate heat treatments. However, further investigation is required to control the porosities of GISS-HPDC samples during heat treatment.

Effect of Pouring Temperature by a Novel Micro Fused-Casting on Microstructure and Properties of ZL101 Semisolid Slurry

Effect of Pouring Temperature by a Novel Micro Fused-Casting on Microstructure and Properties of ZL101 Semisolid Slurry

Characteristics of Pore Morphology in Aluminum Alloy Foams Fabricated by Semi-Solid Route among Multiple Experimental Runs

A semi-solid route is expected to be a fabrication method that can fabricate aluminum alloy foams with a variety of mechanical properties, but the allowance fluctuation of the fabrication conditions of aluminum alloy foams with high reproducibility is not clear. The objective of this study was to reveal the allowance fluctuation between the setting temperature and the actual temperature of the melt to fabricate stable foams, having pores with small pores and high circularity, and the influence of the increasing volume fraction of the solid on the pore morphology. Al-Si alloy foams were fabricated five times by adding a blowing agent into a semi-solid slurry under the same setting fabrication conditions, such as the temperature and concentration of oxygen in the atmosphere. The results of small relative standard deviations of pore diameter and circularity indicated that the conducted fabrication process had high reproducibility, even if the volume fraction of the solid changed in a range of 5%. When the volume fraction of the solid exceeds the minimal fraction of primary crystals for prevention of drainage, the clogging effect works more efficiently because the ratio of clogged cell walls increases. Additionally, the preferred range of the volume fraction of the solid for the fabrication of stable foam was revealed to be around 15% to 35%.

Microstructure, segregation and mechanical properties of A356 alloy components fabricated by rheo-HPDC combined with the swirled enthalpy equilibration device (SEED) process

The challenges commonly associated with conventional high pressure die casting (HPDC) have led to increased interest in semi-solid metal (SSM) forming processes. In the present study, semi-solid slurries of A356 alloy prepared by the Swirled Enthalpy Equilibration Device (SEED) process were used for manufacturing components with complex shape by using a high pressure die casting machine. The segregation phenomenon and the effect of heat treatment on the microstructure evolution and mechanical properties were investigated. The results showed that the alloy consists of primary spherical α-Al grains, secondary solidified α-Al grains, eutectic Si, iron-rich intermetallic phases and low porosities. The microstructural investigations revealed that the eutectic Si particles underwent fragmentation, spheroidization and coarsening with increasing solution temperature. Furthermore, the solution treatment results in the dissolution of the π-Al8FeMg3Si6 phase and the growth of the β-Al5FeSi phase. The hardening peaks at 170 °C could be obtained with ageing for 5 h. Due to both solution and precipitation strengthenings, the yield strength, ultimate tensile strength and hardness of A356 alloy after heat treatment increase significantly compared to those in the as-rheocast state: they reach 266 MPa, 343 MPa and 110 HV0.2, respectively. The analysis of fracture surfaces of rheo-HPDC samples in both the as-rheocast and the heat-treated states revealed a mixed mechanism of dimples and quasi-cleavage. The microstructure inside the part was found to be quasi-homogeneous while the segregation phenomenon in different zones of the part is affected by die geometry during the filling process. The results imply that the SEED-HPDC process has the potential to be industrialized by implementing appropriate heat treatments for producing complex components with good mechanical properties.

Microstructure Design of Semi-Solid Slurry for Metal Direct Writing

Metal direct writing in semi-solid slurry is an innovative technology to realize low-cost printing of load-bearing parts in contrast to laser-based additive manufacturing. However, it is challenging to achieve near net-forming of 3D parts in the current stage because of the out of controlled microstructure and hence the unstable macro extrusion of the used semi-solid slurry. Here, mixed powder remelting (MPR) is introduced to actively design the characteristics of solid phases, i.e., solid fraction, shape factor, and size distribution. Specifically, high-melting-point pure Al powder served as the dispersed solid phases in the liquid phase that transformed from Al-Si alloy powder after remelting, leading to hypoeutectic Al-Si semi-solid slurry. The effectiveness of this approach was experimentally examined and kinetically modelled, to prepare semi-solid slurry with pre-set microstructure. The improved extrusion stability of semi-solid slurry can be anticipated, and it is universal for manufacturing of metal matrix composites slurry.

New Addressable Applications for Rheocasting to Escape from an Oversupplied Market

The current market change of aluminium HPDC castings started with the “Dieselgate”. First, there was a shift from diesel to petrol engines. In the second step, hybrid and battery-powered cars gained significant market shares in sales statistics. Therefore, lucrative powertrain components are falling away. As powertrain foundries still want to utilize their machines to capacity, they are pushing into the structural castings market. As a result, there is an oversupply of casting machines here, which massively depresses prices and, thus, margins for tenders. With rising energy costs, these declining margins were eaten up, bringing foundries into crisis. Implementing Rheocasting at the existing die-casting cells is the solution to move into new market shares that are now not accessible in conventional HPDC.One of the new applications is electronic housings, high wall thickness parts, and fatigue bearing parts. These parts are commonly manufactured in sand or gravity castings because of their high wall thickness and low tolerance of porosity. Rheocasting is the perfect process for high-wall thickness components. Because of the semisolid melt preparation and the lamellar filling behavior, these components can be manufactured from the same alloy without pores or voids.This flow behavior of the semisolid slurry also results in a longer flow length. Slower casting speeds and lower pressure settings result in lower clamping forces. This gives an advantage in production costs and targets battery constructions made of castings and sheet metal. Structural battery housings must be leak-tight, even in a crash event. Having it in one casting instead of an assembly reduces the leakage area and improves crash performance.Another industry that relies on Rheocasting is the telecommunications industry. The power electronics in these 5G modules are significantly larger and generate much more waste heat. Until now, many antennas have been actively cooled or milled from a block of aluminum. The milled housings are significantly too expensive to enable series production. Therefore, the goal is to reproduce the passively cooled modules in die casting. Due to the process, the thermal conductivity in conventional HPDC is around 120 to 130 W/m*K. Similarly, no slim cooling fins can be formed. Only the Rheocasting process makes it possible to cast other alloys with low proportions of alloying elements, such as AlSi2Mn. This allows fins with a wall thickness of down to 0.4 mm and thermal conductivity of up to 190 W/m*K.Rheocasting enables access to market segments out of reach. These bring an unbeatable cost advantage against the current suppliers: gravity and sand casters. The low cycle time in Rheocasting brings back the high margins needed to sustain the business. Also, these products can be delivered with even better properties on smaller casting machines.

A Study on Microstructure and Properties of Aluminum Alloy Bracket Produced by a New Semi-Solid Rheo-Diecasting Process

The performance of bracket component is low with uneven micro-structure, internal porosity and shrinkage defects produced by traditional liquid die casting process which cannot be strengthened by T6 heat treatment. In this paper, the aluminum alloy bracket with high-performance and light weight was prepared by a novel semi-solid slurry preparation technique that included chilling rod stirring and funnel-shaped cylinder device, which rapidly reducing the liquid temperature to near liquidus and realizing explosive nucleation. The effects of pouring temperature and CRS process on the microstructure and mechanical property of bracket were studied by optical microscopy (OM) equipped with polarizing mode and bench failure test. The results show that the as-cast microstructure mainly consists of near-spherical α-Al. And the semi-solid micro-structure was affected by these two critical parameters, the pouring temperature and CRS process. Without the condition of stirring, the micro-structure is typical dendritic with a certain proportion of fine spherical crystals, which was mainly generated during the filling of die casting process. And with the addition of the chilling rod, the finer and more uniform spherical semi-solid micro-structure was obtained with the lower pouring temperature. Based on the above semi-solid process and flow controlling through the mould design and vertical die casting process optimization, the high-performance bracket component without shrinkage can be prepared. Additionally, compared with the liquid die casting process, the internal quality and bench testing force of bracket prepared by CRS vertical die casting process are significantly improved.

Insert Molding of Aluminum Alloy A7075 and Alumina Plate by Semi-Solid Forging

Industrial, electric railway, and automotive applications of inverters and converters use case-type semiconductor packages called power modules. Power modules have multiple joint points, and among them, from the viewpoint of reliability and bonding strength, many studies on metal-ceramic substrate bonding have been reported. Alumina Al203 or aluminum nitride AIN are mainly used for ceramics, and copper or aluminum are mainly used for metals, although alumina and aluminum have a price advantage. The joining methods are generally brazing and AMB (Active Metal Brazing), but there is a need to improve the joint strength, heat dissipation characteristics, and productivity, i.e., a joining method that does not use brazing material. The purpose of this study is to achieve direct joining of alumina A1203 and aluminum alloy A7075, and semi-solid forging [1, 2, 3, 4, 5, 6] was used as the method. The A7075 used in this study is considered to be suitable for this application because of its high strength and thermal conductivity among aluminum alloys. In this study, solid phase ratio 30 % semi-solid forging was actually performed using a servo press and a die, and the results were evaluated by observing the cross section of the fabricated specimens. The punches and dies were circular in shape to ensure uniform spreading of the molten material, and carbon steel S50C with high thermal conductivity was used to quickly dissipate the heat of the semi-solid slurry during the pressing process. The thickness of 99.6 % Al2O3 alumina plate was 2.5 mm. The semi-automatic stirring device was modified to stir the molten metal by attaching a 1000 mm round bar to the rotating part of a tabletop drilling machine and attaching a stirring blade to the tip of the bar. Debonding between aluminum alloy and alumina plate was not confirmed. There was no gap between the aluminum alloy and the ceramic plate.