Alloy Slurry Research Articles

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.

Piezoelectric-pneumatic material jetting printing for non-contact conformal fabrication of high-temperature thick-film sensors

Conformal printing of high-temperature thick-film sensors (TFSs) on intricate surfaces is crucial for precise integration and enhanced functionality. However, traditional contact printing faces challenges in terms of the complex motion control of 3D surfaces. With the core concept of non-contact printing, this study employs piezoelectric-pneumatic material jetting (PPMJ) to achieve rapid and uniform manufacturing of complex and multi-material conformal TFSs. PPMJ enables a wide viscosity range (50–100,000 mPa.s) and high solid content (60 wt%), accommodating various types of inks, from insulating to semiconductor materials to high-temperature alloy slurries, thus providing a broad operational window for shape control and performance modulation in the conformal manufacturing of TFSs on curved surfaces. Microscale shape control of ceramic ink features, including a parallel three-phase contact line, uniform print dimensions, and post-curing shape control, was systematically investigated. PPMJ printing facilitates the successful in situ fabrication of multi-layer TFSs, featuring the self-assembly of droplets and dependable printing consistency, with nozzle-to-substrate heights ranging from 1 to 10 mm, thus advancing the structural arrangement, design, and manufacturing of conformal multi-layer TFSs on curved surfaces. For example, the polymer-derived ceramic heat flux sensor printed by PPMJ demonstrates repeatable high-temperature responsiveness and can be integrated on the surface of turbine blades, withstanding thermal impacts from flames exceeding 800 °C. Hence, PPMJ printing technology opens new possibilities for the conformal manufacturing of various sensors on complex 3D surfaces.

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.

Effect of Ingate Length on Microstructure and Properties of Semi-Solid Squeeze Casting CuSn10P1 Alloy

It is easy to occur solid-liquid separation during semi-solid rheological forming, which leads to poor uniformity of microstructure and properties and limits its application in high strength and toughness parts. In this paper, a semi-solid CuSn10P1 alloy slurry was prepared by an enclosed cooling slope channel (for short ECSC). The effect of ingate length on microstructure and properties by semi-solid squeeze casting was studied. The results showed that the proper increase of the length of the ingate is beneficial to improve the uniformity of the microstructure and properties of the semi-solid squeeze casting. The microstructure uniformity and properties are the best when the ingate length is 20mm. The ultimate tensile strength and elongation of semi-solid squeeze casting CuSn10P1 alloy with 20 mm ingate length reached 419.2 MPa and 13.4%.

Predicting temperature of semi-solid 7075 aluminum alloy slurry prepared by a novel rheocasting route via neural network

The rapid preparation of desired semi-solid slurry with a specific average temperature and a high temperature uniformity is of essential importance for the rheocasting of high-strength aluminum (Al) alloys. In this study, a novel semi-solid slurry preparation process, namely Enthalpy Control Process (ECP), has been proposed for rapid preparation of 7075 Al alloy slurry. The machine learning approach from the aspect of neural network was utilized to predict the average temperature and maximum temperature difference of the Al slurry prepared by ECP. The results indicated that the temperature values predicted by Back Propagation Neural Network optimized by Genetic Algorithm (GA-BPNN) models exhibit an excellent fit with the experimental results. The average relative error and the coefficient of determination for average temperature of were 0.9988 and 0.027%, while the values for the maximum temperature difference were 0.9910 and 3.4%, respectively. The GA-BPNN has a great latent capacity in predicting the temperature of the semi-solid slurry.

Enhanced comprehensive performance via alloying and rheo-diecasting in a semi-solid Al–Si–Fe–Mg–Cu–Sr alloy

A semi-solid Al alloy with superior comprehensive performance was obtained via alloying design concept and rheo-diecasting (RDC). The semi-solid alloy slurry was obtained via the vibrating contraction sloping plate. As the contents of Cu and Mg elements increased, the secondary dendrite arm spacing (SDAS) decreased and solubility of Cu and Mg elements increased, which improved the mechanical property and decreased the thermal conductivity of as-cast alloys. The effect of microstructure evolution induced by pouring temperature on mechanical properties at room and elevated temperatures, thermal conductivity, and corrosion behavior of the RDC alloy was investigated. The results demonstrated that the low porosity and refined primary α1-Al grains, secondary α2-Al grains, β-Al5FeSi phases, eutectic Si phases played a significant role in enhancing mechanical properties of the alloy at room temperature. Meanwhile, some submicron β-Al5FeSi phases effectively hindered grain boundary sliding, resulting in the increased mechanical properties of the alloy at elevated temperatures. The improvement in thermal conductivity was related to the decreased electron scattering due to the reduced porosity and small-sized secondary phases. The decrease in the potential difference between the β-Al5FeSi phase and matrix helped improve the corrosion resistance of the alloy.

Influence of slurry delivery rate and height from cooling slope outlet on solidification and structural behaviors of molded AZ91 magnesium alloy

AZ91 magnesium alloy melt experiences partial solidification while flowing on cooling slope with counter flowing water channel underside. It results in continuous production of semisolid slurry available at cooling slope outlet. Current experimental investigations pertain to the influence of slurry delivery rate and slurry delivery height from cooling slope outlet on solidification and structural behaviors (microstructure along with mechanical properties) of AZ91 magnesium alloy intended for semisolid casting. Slurry delivery rate along with slurry delivery height warrant necessary solidification and shear for grain growth and globularization within metal mold for producing semisolid casting. Moderate slurry delivery rate of 0.025 kg/s along with slurry delivery height of 150 mm results fairly modest solidification that would greatly contribute toward enhanced structural behaviors. As, quite smaller/bigger slurry delivery rate/height generate low shear due to slurry flow inertia or accelerated slurry flow resulting stick-slip flow/motion of alloy slurry on cooling slope. It results poorer structural behaviors amid extremely unwanted casting issues. As, throughout the course escape/retain of metal with gas arise. Since, lesser slurry delivery rate/height allows metal to escape thereby reduces strength and vice-versa. Additionally, lesser slurry delivery rate/height allows gas to escape thereby enhances strength and vice-versa. Therefore, moderate cooling slope casting parameter magnitudes guarantee solution to bewilderment.

Direct Ink Writing of Porous Ti6Al4V Alloys via UV Light Curing

Although 3D printing of titanium alloys is often obtained by laser fusion deposition, its cost is relatively high. In this study, one light‐curing‐assisted technique is designed to print porous Ti6Al4V alloys via direct ink writing (DIW). For printing, titanium alloy slurry with 45 vol% solid content is prepared based on 1,6‐hexanediol diacrylate monomer‐trimethylolpropane triacrylate monomer (HDDA‐TMPTA) photosensitive system. In such a case, the extruded filament was in situ cured under the action of UV light irradiation in the printing process. The printed lattice sample has good surface performance without the observation of a collapse. After sintering, the shrinkage percentage is around 16% in the horizontal direction and 19% in the vertical direction. Surface morphology does not change significantly. Through comparative tests, it is found that the sintered samples have good microstructure and mechanical properties. When the filling rate is 50%, the compressive strength could reach 604.7 MPa and the flexural strength is 106.8 MPa. The feasibility of this new printing method to prepare titanium alloy parts are confirmed.

Microstructure, segregation and fracture behavior of 6061 aluminum alloy samples formed by semi-solid or traditional high pressure die casting

A serpentine channel pouring (SCP) process for efficiently preparing semi-solid 6061 aluminum alloy slurry and its rheological high pressure die casting (Rheo-HPDC) technology were introduced. The microstructure, segregation and fracture behavior of 6061 aluminum alloy samples obtained via the traditional HPDC or Rheo-HPDC process were investigated and compared. Furthermore, the effects of pouring temperature and Si content on the distribution, grain size and volume fraction of the primary phase were analyzed. The results indicated that the Rheo-HPDC process can effectively refine and improve the morphology of the primary phase compared with the traditional HPDC samples, which evolved from coarse dendrites into fine spherical grains. The pouring temperature had a significant effect on the primary α1-Al grains during slurry preparation, but had little effect on the secondary solidified α2-Al grains in the Rheo-HPDC samples. Moreover, with increasing Si content, the casting capability of the alloy was significantly enhanced, while the grain size of the primary phase was no obviously changed. Additionally, the liquid segregation led to varying microstructures, elemental distributions and fracture mechanisms of the samples. The volume fraction of the primary phase increased with increasing the distance from the sample surface, while the Si, Mg, Fe and Cu contents were enriched at edge of the testing bars. Besides, the liquid segregation tendency gradually increased along the filling direction in the Rheo-HPDC samples. Under the same die casting process parameters, the Rheo-HPDC samples had excellent mechanical properties than that of the traditional HPDC samples, and its ultimate tensile strength (UTS) increased from 90.8 MPa to 106.9 MPa. The fracture mechanism of the traditional HPDC samples was mainly brittle quasi-cleavage fracture, while the Rheo-HPDC samples was mainly mixed-fracture mechanism of dimple and quasi-cleavage fracture.

Preparation of semi-solid 6061 aluminum alloy slurry by serpentine channel pouring

The semi-solid 6061 aluminum alloy slurry was prepared by a serpentine channel pouring process. The effects of pouring temperature, bend number and bend diameter on the microstructures were investigated. Microstructural evolution mechanism of the semi-solid slurry during the pouring process was also analyzed. The results show that the grain is refined and the grain roundness is improved by controlling the pouring temperature close to the liquidus temperature, and the nucleation rate of primary α(Al) grains is effectively increased via increasing the bend number and decreasing the bend diameter. The primary grains are not only formed directly from the alloy melt via chilling nucleation and heterogeneous nucleation, but also evolved from the fractured dendrite fragments. Meanwhile, the heat exchange between the melt and the serpentine channel is increased by the “self-stirring” effect in the melt, which also promotes the refinement and spheroidization of primary α(Al) grains.

Effect of Serpentine Channel Pouring Process on the Microstructure of Semi-Solid 6061 Aluminum Alloy Slurry

The semi-solid slurry of 6061 aluminum alloy was prepared by the serpentine channel pouring process. The influence of graphite serpentine channel and copper serpentine channel on the slurry was comparative analyzed. The effect of pouring temperature on the slurry microstructure was also investigated. The results indicate that both copper and graphite serpentine channel can be used to prepare semi-solid slurry with spherical primary grains. Compared with a permanent casting, the microstructure of the semi-solid slurry was significantly improved and refined. With the increase of pouring temperature, the average equivalent grain diameter of the primary phase grains in the semi-solid slurry increases gradually, but the shape factor decreases gradually. When the pouring temperature increased from 675 °C to 690 °C, a high quality semi-solid slurry can be obtained. Comparing the two kinds of serpentine channel, it is found that the copper serpentine channel can make the primary grains finer, and the average equivalent grain size was 63 μm. However, the solidified shell near the inner graphite serpentine channel surface was thinner than that of the copper serpentine channel. In conclusion, the graphite serpentine channel is more suitable for preparing semi-solid 6061 aluminum alloy slurry.

Effect of Runner Distance on Microstructure and Properties of Semi-Solid Squeeze Casting CuSn10P1 Alloy

It is easy to form reverse segregation and shrinkage porosity defects during the solidification of CuSn10P1 alloy, which leads to the poor properties and limits its application in high strength and toughness parts. In this paper, semi-solid CuSn10P1 alloy slurry was prepared by enclosed cooling slope channel (for short ECSC). The effect of runner distance on microstructure and properties by liquid squeeze casting and semi-solid squeeze casting was studied. The results showed that the microstructure of semi-solid squeeze casting is finer than that of liquid squeeze casting, and the shrinkage defects are improved. The solid fraction with 65 mm runner is lower than that without runner in liquid squeeze casting and semi-solid squeeze casting due to the retention effect of solid phase in semi-solid slurry flow, but the properties with 65 mm runner is better than that without runner. The ultimate tensile strength, yield strength and elongation of semi-solid squeeze casting CuSn10P1 alloy with 65 mm runner distance reached 466.5 MPa, 273.6 MPa and 13.4%, which were improved by 26%, 19% and 97%, respectively, as compared to that of liquid squeeze casting.

Characterizing the Effect of Processing Parameters on Temperature Distribution of 7075 Aluminum Alloy Slurry Prepared by Enthalpy Control Process

There is a strong demand for high-strength aluminum alloys such as 7075 aluminum alloy to be applied for rheocasting industry. The overriding challenge for the application of 7075 alloy is that its solid fraction is very sensitive to the variation of temperature in the range of 40% ~ 50% solid fraction, which inevitably narrows down the processing window of slurry preparation for rheocasting process. Therefore, in this work, a novel method to prepare semi-solid slurry of the 7075 alloy, so called Enthalpy Control Process (ECP), has been developed to grapple with this issue. In the method, a medium-frequency electromagnetic field was applied on the outside of slurry preparation crucible to reduce the temperature difference throughout the slurry. The effect of processing parameters, including heating power, heating time, the initial temperature of crucible and melt weight, on the temperature field of the semi-solid slurry was investigated. The results exhibited that although the all the processing parameters had a great influence on the average temperature of the slurry, heating time was the main factor affecting the maximum temperature difference of the slurry. The optimum processing parameters during ECP were found to be heating power of 7.5 KW, the initial temperature of crucible of 30 °C ~ 200 °C and melt weight of 2 kg.

Semi-Solid 6061 Aluminum Alloy Slurry Prepared by Serpentine Channel Pouring Process and its Rheo-Diecasting

Semi-solid 6061 aluminum alloy slurry was prepared by a graphite serpentine channel and its rheo-diecasting experiment was carried out on the slurry. The influence of pouring temperature on the microstructure evolution and mechanical properties of the rheo-diecasting were investigated. The microstructure and fracture mechanism of traditional die cast tensile specimens and rheo-diecast tensile specimens were compared and investigated. The results indicate that the microstructure of rheo-diecast tensile specimens is composed of spherical primary α-Al grains and fine secondary solidified α2-Al grains. When the pouring temperature increased from 660 °C to 720 °C, the average equivalent grain diameter of primary α-Al grains increased from 42 μm to 58 μm, and the shape factor decreased from 0.82 to 0.73. As the pouring temperature increases, the as-cast tensile strength and elongation of tensile specimens both increase first and then decrease. When the pouring temperature was 690 °C, the best mechanical properties were obtained, with as-cast tensile strength of 142.93 MPa and as-cast elongation of 4.86%. The fracture mechanism of traditional die casting is mainly ductile fracture, and the fracture mechanism of rheo-diecasting is a mixed fracture of intergranular fracture and ductile fracture.

THE EFFECT OF PARTICLES MORPHOLOGY ON THE DAMPING CAPACITIES OF AZ91D-FAC COMPOSITES

Four kinds of magnesium matrix composites were prepared by stirring casting method with various additions to the AZ91D Mg alloy slurry: 10 wt.% of fly ash cenospheres (FAC), two kinds of particle (average size 60 and 120 μm, and two kinds of particle morphology (ball-milled to powder fragments and non-ball milled). The effect of the particle integrity and particle size of FAC on the phases, microstructure, and damping capacities of the composites was investigated. The X-ray diffraction (XRD) patterns and microstructure show that new phases were produced. The damping measurement results illustrate that with the particle size increasing, the damping capacities of the composites increase, and ball-milled FAC particles have greater effect on the damping capacities than non-ball milled particles at both 20°C and elevated to 320°C. Moreover, the particle morphology has a 15% greater impact on damping capacities than the particle size at room temperature and 8% greater at elevated temperature.

Microstructure Evolution and Solidification Behavior of a Novel Semi-Solid Alloy Slurry Prepared by Vibrating Contraction Inclined Plate

In this work, based on the A356 alloy, a novel Al–Si–Mg–Cu–Fe–Sr alloy with good mechanical property and high thermal conductivity was developed. The semi-solid slurry of the alloy was prepared via the vibrating contraction inclined plate. The microstructure evolution and solidification behavior of the alloy were investigated. The results demonstrated that, compared with the A356 alloy, the enhanced property of the Al–Si–Mg–Cu–Fe–Sr alloy was associated with the size of primary α-Al grains and morphology of eutectic Si phases. In addition, the preparation process parameters of semi-solid slurries, including the pouring temperature, inclination angle, and vibration frequency, had a crucial effect on the size and morphology of primary α-Al grains. The optimized pouring temperature, inclination angle, and vibration frequency were 670 °C, 45°, and 60 Hz, respectively. In this condition, for the primary α-Al grains, a minimum grain diameter of 64.31 µm and a maximum shape factor of 0.80 were obtained. This work provides a reference for the application of the alloy with high performance in the field of automobile and communication.

Globularization of Primary Phase of Al–7Si–0.3Mg Alloy During Cooling Slope Processing and Isothermal Holding

This study is aimed towards process design for semi-solid slurry generation of Al–7Si–0.3Mg alloy using cooling slope as a slurry maker, and subsequent isothermal holding to promote globularization of slurry microstructure. The study primarily reports globularization mechanism of cooling slope processed semi-solid slurry of the alloy, and efforts are directed to establish process control by investigating the effect of coarsening during isothermal holding on the shape, size and distribution of primary Al grains. As an outcome of this study, we propose a modified Lifshitz–Slyozov Wagner equation to quantify the effect of coarsening mechanisms prevailing during isothermal holding of the said alloy slurry. The evolution of primary phase morphology due to addition of grain refiner has also been studied and ideal processing condition is identified for the end goal of component development through rheo pressure die casting route.

Study on Formation of Microstructure in Rheo-Diecastings of Semi-Solid A380 Aluminum Alloy Slurry

The formation of the microstructure in the rheo-diecastings were studied by the experiment of rheo-diecasting with semi-solid A380 Aluminum alloy slurry. The results show that the grain diameter and shape factor of primary α-Al grains decreased and increased along the rheo-diecasting direction, respectively, making the primary α-Al grains gradually distributing uniformly. The combination of injection pressure and narrow gate of the runner and ingate was the main reason for the evolution of the primary α-Al grains, moreover, the collision and friction among primary α-Al grains during the filling were helpful for the refinement and spheroidization of the primary α-Al grains. The residual liquid solidified into the secondary solidification microstructure accompanied by the evolution of the primary α-Al grains. The accumulation of the fragments of the primary α-Al grains, the secondary α2-Al nuclei or grains which formed in previous positions, the effective nucleation rate of the residual liquid, and the collision and fraction among the secondary α2-Al grains and between the secondary α2-Al grain and the primary α-Al grains made the secondary solidification microstructure of the residual liquid present multiplex and complicate characteristics. In this paper, the formation of the microstructure in the rheo-diecastings were studied by the experiment of rheo-diecasting. During the rheo-diecasting, the grain diameter and shape factor of primary α-Al grains decreased and increased, respectively along the rheo-diecasting direction, which made the primary α-Al grains gradually distribute uniformly. The drifting of the fragments of the primary α-Al grains and secondary α2-Al nucleus, and the effective nucleation rate of the residual liquid played an important effect on the morphology of the secondary solidification structure.

Study on Semi-Solid A380 Aluminum Alloy Slurry Prepared by Water-Cooling Serpentine Channel and Its Rheo-Diecasting

The semi-solid A380 aluminum alloy slurry prepared by water-cooling serpentine channel and its rheo-diecasting were studied in this paper. The result showed that the pouring temperature and cooling water flow rate had a significant effect on the semi-solid slurry. When the pouring temperature decreased from 670 to 610 °C, the average grain diameter and shape factor of the primary α-Al grains decreased from 64 to 47 µm and increased from 0.74 to 0.82, respectively, but the mass of semi-solid slurry blocked in channel increased. With the cooling water flow rate increasing from 0 to 1000 L/h, the semi-solid slurry firstly got optimized and then deteriorated. Under the condition of the same die casting process parameters, the rheo-diecastings produced by the semi-solid slurry prepared through water-cooled serpentine channel had higher mechanical properties than those of the traditional die castings. In this work, a new simple and low cost preparation of semi-solid slurry was invited, which was suitable for rheological forming of the short process. What's more, the rheo-diecasting was studied through comparing the traditional die casting. The result showed that the pouring temperature and cooling water flow rate had a significant effect on the semi-solid slurry. When the pouring temperature decreased, the average grain diameter and shape factor of the primary α-Al grains increased and decreased respectively. With the cooling water flow rate increasing, the semi-solid slurry firstly got optimized and then deteriorated. Under the condition of the same die casting process parameters, the rheo-diecastings produced by the semi-solid slurry prepared through water-cooled serpentine channel had higher mechanical properties than those of the traditional die castings.

Evaluation of Microstructural Characteristics of High-Si Al Alloy Cylindrical Samples Produced by Rheological Squeeze Casting with Bottom-Up Filling and Flow State Analysis of the Alloy Semi-Solid Slurries

The microstructures of high-Si Al alloy cylindrical simples produced by rheological squeeze-casting with bottom-up filling were investigated. The effect of process parameters on the distribution of hard phases (primary Si and Fe-rich phase) was evaluated, and flow characteristics of semi-solid slurry of high-Si Al alloy were investigated. Differences in volume fractions (VFs) of hard phases between the middle and upper layers of cylindrical samples decreased as the squeezing speed increased. Moreover, the flow state of the semi-solid alloy slurry transitioned from laminar to turbulent flow as the squeezing speed was increased. Movement of gases throughout the semi-solid alloy slurry filling process was analysed under different process parameters. The results provide insights for improving rheological casting of high-Si Al alloy and other Al matrix composites.