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Microstructure of A356 aluminum alloy: (a) initial A356 alloy, (b) A356 alloy after vibration, and (c) A356 + 0.5 wt% TiB 2 after vibration treatment.
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A series of casting experiments was conducted with A356 aluminum alloys by applying vibration treatment and using Al-TiB2 composite master alloys. The main vibration effects include the promotion of nucleation and a reduction in as-cast grain size. Using composite master alloys with titanium diboride microparticles allows further reduction in the a...
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Citations
... While magnetic springs resist mechanical fatigue and demand less energy for initial movement, they present a challenge of amplitude regulation under constant resonance conditions. This limitation underscores the complexity of designing dosing systems that balance the benefits of resonance resistance with the need for amplitude control [2,[15][16][17][18][19]. ...
In the industrial and sales processes, dosing systems of various constructions, whose operation is based on mechanical vibrations (vibratory feeders), are very often used. These systems face many problems, such as resonant frequency, flow instability of dosed product, instability of mechanical vibration amplitude, etc., because most of them are based on controlling the frequency of the electrical signal of the supply voltage. All these factors negatively affect the durability and reliability of the vibratory feeder systems. During this research, an automatic control system for vibratory feeder was created, whose control process is based on the modification of the sinusoidal signal (partially changing the signal area). In addition, such a way of controlling the vibratory feeder is not discussed in the literature. As the research conducted in this paper has shown, while using sinusoidal signal modification it was possible to achieve a stable flow rate of bulk production (the flow rate varied from 0 to 100 g/s when the frequency of mechanical vibrations changed from 1 to 50 Hz) and a stable amplitude of mechanical oscillations was achieved and equal to 1.5 mm. The control system is based on the microcontroller PIC24FV32KA302 for which the special software was developed. The thyristor BTA16 used for voltage modification of the sinusoidal signal made it possible to ensure the reliable control of the sinusoidal voltage modification process.
... As a result, ingots of small grains are more homogeneous in their solidification microstructure, easier to be hot worked, and higher in quality in the resultant forgings than that of corse grains. Consequently, metallurgists have developed a variety of methods to control ingot solidification, including using-exothermic risers, [6][7][8] multi-pouring processes, [9] mechanical oscillations, [10,11] adding chilling balls, [12] ultrasonic treatments, [13][14][15][16] electromagnetic stirring, [17][18][19] and pulsed currents. [20][21][22] Exothermic risers have been found to decrease shrinkage by enhancing feeding effects, and multi-pouring processes have been found to reduce macrosegregation by controlling the composition of molten steel of each ladle. ...
We scaled up a previously developed method, known as Hot-top Pulsed Magneto-Oscillation (HPMO), to minimize crack, shrinkage-cavity, and macrosegregation in large ingots. Simulations on electromagnetic field, flow field, and temperature field revealed that an HPMO-induced electromagnetic field forces circulation of liquid steel near the riser, which causes grain nuclei and free grains to fall off the riser walls, drift away, and settle onto the middle of the mold. This phenomenon, known as “grain showering”, refines solidified structure and reduces segregation. Joule heating generated by the HPMO process leads to mass feeding of the riser, which eliminates the development of pipes or central porosity and cracks. Based on simulation results, we designed a prototype HPMO apparatus and tested it on the production of ingots weighing 18 tonnes. Experimental results indicated that the use of HPMO grain showering did indeed yield expected solidified structure in ingots with a 56–83 pct reduction in equiaxed grain size, a 41 pct reduction in the number of inclusions, and a 50–75 pct reduction in normal carbon segregation comparing with that in controlled ingots. Furthermore, by using HPMO, shrinkage-induced pipes and center cracks that often occurred in the control ingots were eliminated, resulting in a fourfold increase in ductility in critical regions of the ingot. This work demonstrated the value of computation-aided simulation for improving manufacturing methods for the casting of large ingots.
... When the TiB2-added A356 composite sample was examined, it was concluded that the mechanical properties were improved compared to the vibrating A356 aluminum alloy. [9] In the study published by Selivorstov et al. in 2017, vibration at 100 Hz, 150 Hz and 200 Hz levels were applied to A356 and A 356 with ultrafine powder modifier modification. At 100 and 150 Hz, 20% and 10% improvement were observed in tensile and yield strength, respectively, compared to non-vibration samples. ...
Manufacturing by casting method in aluminum and its alloys is preferred by different industries today. It may be necessary to improve the mechanical properties of the materials according to different industries and different strength requirements. The mechanical properties of metal alloys are directly related to the microstructure grain sizes. Therefore, many grain reduction methods are used during production or heat treatment. In this study, A356 alloys were molded into molds at 750 °C and exposed to vibration frequency at 0, 8.33, 16.66, 25, and 33.33 Hz during solidification. Optical microscopes images were analyzed in image analysis programs to measure the grain sizes of the samples that solidified after solidification. In addition, microhardness tests of samples were carried out to examine the effect of vibration and grain reduction on mechanical behavior. In the analyzes made, it was determined that the grain sizes decreased from 54.984 to 26.958 μm and the hardness values increased from 60.48 to 126.94 HV with increasing vibration frequency.
... 26 Furthermore, mechanical vibration had a significant impact on the mechanical properties and the interfacial microstructure of a Mg/Al bimetal, but it had no effect on the phase compositions of the interface. 27,28 Numerous researchers suggest that the mechanical vibration technique can be used to refine the microstructure of solids during solidification because they are simple to use and can be used to produce complex shapes. 29 Furthermore, ultrasonic vibration treatment is a quick and efficient physical technique for controlling the process of solidification. ...
Mg–Zn–Ca alloys have been widely used as biodegradable orthopedic and cardiovascular scaffolds because of their non-cytotoxicity, remarkable biodegradability, good biocompatibility and excellent mechanical properties similar to human bone. However, degradation causes poor corrosion resistance and mechanical properties. In this study, Mg-6%Zn-0.6%Ca alloys were produced using three distinct methodologies: casting, casting via the ultrasonic vibration process (USV), and casting via the mechanical vibration process (MV). Surface characterization, mechanical characteristics and corrosion resistance of the as-cast (untreated) and treated species were studied. The morphology and microstructure showed that the grain size of the as-cast, MV and USV specimens all had average grain sizes of about 191, 93 and 82 µm, respectively. The ultrasonic vibration treated specimen has the greatest degree of grain refinement. Mechanical tests showed that microstructure refinement promotes the mechanical characteristics of Mg alloy, such as compression, ultimate tensile strength as well as elongation. It was observed that the USV-treated sample has exceptional mechanical properties (Compressive strength 360.64 MPa, ultimate tensile strength (UTS) 178.41 MPa and Elongation 3.45%). Corrosion tests revealed that the USV-treated specimen exhibited uniform corrosion and low corrosion rate due to uniform compact fine grains with higher oxide concentration of about 42.82 wt%. The results of electrochemical analyses revealed that the average corrosion rate obtained from Potentiodynamic polarization curves of the as-cast, MV and USV specimens was about 5.3144, 4.5311 and 4.1087 mm/year, respectively and the passive film resistance ( R f ) that was obtained from the electrochemical impedance spectroscopy (EIS) model of the USV, MV-treated samples and as-cast sample was 457 Ω, 430 Ω and 204 Ω, respectively. The results of immersion tests revealed that the USV-treated sample lost less weight and exhibits a relatively low degradation rate than the as-cast and MV-treated samples. After two weeks the weight of the as-cast, MV and USV samples decreased by about 18.6%, 18.5%, 16.8%., and the degradation rates were 7.304, 7.097 and 6.78 mm/y, respectively, and then gradually declining over the course of the immersion period.
... Scholars ascribe the change in feeding caused by vibration to a variety of factors. Some researchers consider that mechanical vibrations can promote the crystal nuclei that are generated on the mold wall and upper surface after casting [5,6], reduce the growth rate of dendrites [7], increase the cooling rate [8], and promote forced convection to melt the dendrites [9,10], eventually leading to grain refinement. The refined grains are more easily fed into the casting [11], thereby reducing shrinkage defects. ...
The wave field in solidifying metals is the theoretical basis for analyzing the effects of mechanical vibration on solidification, but there is little research on this topic. This study investigated the wave field and its effect on the solidification feeding in the low-pressure sand casting (LPSC) of Al-Cu-Mn-Ti alloy through experimental and numerical investigation. The solidification temperature field was simulated by AnycastingTM, and the wave field was simulated by the self-developed wave propagation software. The shrinkage defect detection showed that applying vibration had a greater promotional effect on feeding than increasing the holding pressure. The predicted defects under vibration coincided with the detections. The displacement field showed that the casting vibrated harmonically with an inhomogeneous amplitude distribution under the continuous harmonic vibration excitation, and the vibration energy was mainly concentrated in the feeding channel. With solidification, the ux amplitude reduced rapidly after the overlapping of dendrites, finally reducing slowly to a certain level; the uy amplitude reduced dramatically after the occurrence of a quasi-solid phase, finally reducing slowly to near zero. Mechanical vibration produced a severe shear deformation in the quasi-liquid phase—especially in the lower feeding channel—reducing the grain size to promote mass feeding. The feeding pressure and feeding gap were changed periodically under vibration, causing the vibration-promoting interdendritic feeding rate to fluctuate and eventually stabilize at about 13.4%. The mechanical vibration can increase the feeding pressure difference and change the blockage structure simultaneously, increasing the formation probability of burst feeding.
... Mechanical vibration, as an excellent plugging removal technology, is widely used in oil exploitation [16] and also has been applied in casting to ameliorate solidification [17][18][19]. Yadav [20] and Jiang et al. ...
... As compared with sample 1, the grain sizes of samples 2-4 reduced by 7.2%, 15.2%, and 29.5%, respectively. The refinement of the mechanical vibration in the aluminum castings was observed generally by researchers in gravity castings [18][19][20][21][22][23][24]. The same refinement effect on the LPSC castings was firstly observed in our experiments. ...
The shrinkage defects of Al-Cu-Mn-Ti alloy seriously hinder its application in high-performance engineering. In this study, mechanical vibration was introduced to low-pressure sand casting (LPSC) by a waveguide rod to eliminate shrinkage defects and improve mechanical properties. Four LPSC castings were performed by changing the solidification conditions: 20 kPa solidification pressure without and with 14 Hz vibration and 40 kPa without and with 24 Hz (the natural frequency of a casting system) vibration. The shrinkage defects, microstructures, and mechanical tensile properties at room temperature and at 2 mm/min tensile rate were investigated. X-ray detections showed that applying vibration was more effective than increasing solidification pressure in improving solidification feeding, while the most effective method was applying both simultaneously, which eliminated the shrinkage defects and increased the density by 2.7%. Microstructures exhibited that the average size of primary α-Al grains were reduced by 29.5%; mechanical tests showed that the ultimate tensile strength and the elongation increased by 21.7% and 7.8%, respectively, by applying vibration and increasing the solidification pressure simultaneously, as compared to the casting with 20 kPa solidification pressure without vibration. Mechanical vibration was conducive to mass feeding by refining the primary grains, to interdendritic feeding by reducing the threshold pressure gradient, and to burst feeding by collapsing the barrier.
... The tumbling process has a distinctive feature: in addition to mechanical removal of material, process kinematics cause the surface layers of the metal to compact thus forming residual compressive stresses. This effect contributes to an increase in fatigue strength, corrosion resistance, and surface microhardness [109,110]. It should be noted that there are virtually no studies devoted to research on the influence of the technological capabilities of tumbling on the characteristics of AM-fabricated 316L steels. ...
... In article [109], the authors present the results of a study on the reduction of the roughness of the internal surfaces of parts made of an AM-produced 316L steel. Thus, the possibility of a uniform decrease in roughness parameter Ra from 15 to 0.4 µm was determined. ...
... Article [109] presents the results of studies on the effect of electrochemical polishing of stainless chromium steel with the addition of abrasive particles to the electrolyte. In the article, information on the optimal composition of a suspension consisting of oxalic acid, hydrogen peroxide, and certain content of silicon oxide is given. ...
With a vista of available stainless steel grades at our disposal, it is possible to manufacture items for a wide range of industries. These include chemicals production, medicine, and pharmacology, aerospace, power engineering, etc. Stainless steels are widely used mostly due to their unique property set, both mechanical and physicochemical ones, achieved by alloying various components. Stainless steel workpieces are usually obtained by melting, alloying, casting, and subsequent rolling to the desired shape. The experience in the study of the microstructure and processes of physical treatment of steel accumulated to the present day mainly concerns the machinability (blade, abrasive, laser, etc.) of such steels obtained by conventional techniques. Meanwhile, approaches to the production of workpieces from stainless steels by additive manufacturing (AM) methods are actively developing. In their turn, additive manufacturing technologies allow for producing workpieces that are structurally as close as possible to the final product shape. However, the use of AM workpieces in the manufacturing of functional products brings questions related to the study of the treatability of such steels by mechanical and physical processes to achieve a wide range of functional characteristics. This article discusses the issues of treatability and the characteristics and properties of stainless steels obtained by AM.
... However, at the same time, an increase in plasticity occurs with the introduction and increase in the content of tungsten nanoparticles. In [37], a similar relationship was observed for an aluminium alloy when the yield strength, ultimate tensile strength, and ductility increased. It is assumed that the introduction of particles into the grain body can result in a deviation of a potential crack from the grain boundary into its bulk, as well as in greater involvement of the metal matrix in the process of deformation and fracture [38,39]. ...
This paper investigates the impact of tungsten nanoparticles on the microstructure and mechanical properties of the Al-5Mg alloy. Tungsten concentrations of up to 0.5 wt.% led to a slight modification of the Al-5Mg alloy microstructure, and grain refinement occurred due to the inhibition of crystal growth along the boundaries. Dispersion hardening with tungsten nanoparticles made it possible to increase the ultimate strength by the Orowan mechanism with a simultaneous increase in the plasticity of the Al-5Mg alloy. An increase in the tungsten content to 0.8 wt.% made it possible to modify the microstructure of the Al-5Mg alloy, due to the formation of the Al12W phase and an increase in crystallisation centres. The modification of the microstructure, as well as dispersion strengthening by nanoparticles, led to a simultaneous increase in the yield strength, ultimate tensile strength, and ductility of the Al-5Mg alloy.
... At the same time, the flow caused by the melt also leads to the transport process of the solid phase and an increase in crystal nucleation. Therefore, it promotes the formation of more uniform fine-grained solidification microstructures [31]. Moreover, the vibration can also affect the distribution and shape of precipitates by promoting the element diffusion and solute exchange in the bimetallic interface [32]. ...
Vibration was adopted to enhance the interface bonding of Mg–Al bimetal prepared by the lost foam compound casting (LFCC) technique. The Mg–Al bimetallic interface was composed of three layers: layer I (Al3Mg2 and Mg2Si phases), layer II (Al12Mg17 and Mg2Si phases), and layer III (Al12Mg17 + δ-Mg eutectic structure). With the increase in vibration acceleration, the cooling rate of the Mg–Al bimetal increased, resulting in the decrease in the reaction duration that generates the intermetallic compounds (IMCs) layer (including layers I and II) and its thickness. On the other hand, the Mg2Si phase in the IMCs layer was refined, and its distribution became more uniform with the increase in the vibration acceleration. Finally, the shear strength of the Mg–Al bimetal continued to increase to 45.1 MPa when the vibration acceleration increased to 0.9, which was 40% higher than that of the Mg–Al bimetal without vibration.
... It is assumed that the introduction of particles into the grain body can lead to a deviation of a potential crack from the grain boundary into its volume, as well as to a greater involvement of the metal matrix in the process of deformation and fracture [31,32]. In addition, the introduction of tungsten nanoparticles leads to an increase in the hardness and microhardness (Table 1) of the AA5056 from 58 to 63 HB and from 67 to 85 HV, respectively. ...
The paper investigates the effect of tungsten nanoparticles on the structure and mechanical properties of aluminum 5056 alloy. Using optical and scanning electron microscopy, the structure of the AA5056-W composite and the initial alloy is investigated. Introduction of 0.5 wt. % of tungsten nanoparticles does not modify the structure of the aluminum alloy, but due to dispersed hardening, it can increase the hardness and the values of the yield stress, ultimate tensile strength, and maximum deformations before fracture of the metal matrix. The Orowan mechanism prevails in increasing the machinical properties of aluminum 5056 alloy with dispersed hardening with tungsten nanoparticles. The destruction of materials is caused by the uneven distribution of tungsten nanoparticles in the aluminum matrix.KeywordsDispersion-hardened alloysNanosized particlesTungstenAluminumStructureMechanical properties
