Ultrasonic Cavitation Process Research Articles

The role of ultrasonic cavitation in refining the microstructure of aluminum based nanocomposites during the solidification process

Recent studies showed that the microstructure and mechanical properties of aluminum based nanocomposites can be significantly improved when ultrasonic cavitation and solidification processing is used. This is because ultrasonic cavitation processing plays an important role not only in degassing and dispersion of the nanoparticles, but also in breaking up the dendritic grains and refining the as-cast microstructure.In the present study, A356 alloy and Al2O3 nanoparticles are used as the matrix alloy and the reinforcement, respectively. Nanoparticles were added into the molten A356 alloy and dispersed via ultrasonic cavitation processing. Ultrasonic cavitation was applied over various temperature ranges during molten alloy cooling and solidification to investigate the grain structure formation and the nanoparticle dispersion behavior. Optical Microscopy and Scanning Electron Microscopy were used to investigate in detail the differences in the microstructure characteristics and the nanoparticle distribution. Experimental results indicated that the ultrasonic cavitation processing and Al2O3 nanoparticles play an important role for microstructure refinement. In addition, it was shown in this study that the Al2O3 nanoparticles modified the eutectic phase.

In situ observation of ultrasonic cavitation-induced fragmentation of the primary crystals formed in Al alloys

The cavitation-induced fragmentation of primary crystals formed in Al alloys were investigated for the first time by high-speed imaging using a novel experimental approach. Three representative primary crystal types, Al3Ti, Si and Al3V with different morphologies and mechanical properties were first extracted by deep etching of the corresponding Al alloys and then subjected to ultrasonic cavitation processing in distilled water. The dynamic interaction between the cavitation bubbles and primary crystals was imaged in situ and in real time. Based on the recorded image sequences, the fragmentation mechanisms of primary crystals were studied. It was found that there are three major mechanisms by which the primary crystals were fragmented by cavitation bubbles. The first one was a slow process via fatigue-type failure. A cyclic pressure exerted by stationary pulsating bubbles caused the propagation of a crack pre-existing in the primary crystal to a critical length which led to fragmentation. The second mechanism was a sudden process due to the collapse of bubbles in a passing cavitation cloud. The pressure produced upon the collapse of the cloud promoted rapid monotonic crack growth and fast fracture in the primary crystals. The third observed mechanism was normal bending fracture as a result of the high pressure arising from the collapse of a bubble cloud and the crack formation at the branch connection points of dendritic primary crystals. The fragmentation of dendrite branches due to the interaction between two freely moving dendritic primary crystals was also observed. A simplified fracture analysis of the observed phenomena was performed. The specific fragmentation mechanism for the primary crystals depended on their morphology and mechanical properties.

Processing and Microstructure Characteristics of As-Cast A356 Alloys Manufactured via Ultrasonic Cavitation during Solidification

AbstractRecent studies have showed that the microstructure and mechanical properties of A356 alloy can be significantly improved when ultrasonic cavitation and solidification processing is used. This is because during the fabrication of A356 castings, ultrasonic cavitation processing plays an important role in degassing and refining the as-cast microstructure. In the present study, A356 alloy and Al2O3/SiC nanoparticles are used as the matrix alloy and the reinforcements, respectively. Nanoparticles are injected into the molten alloy and dispersed by ultrasonic cavitation. Ultrasonic cavitation was also applied during solidification of these nanocomposites. The microstructure and nanoparticle distribution of the cast samples have been investigated in detail. The current experimental results indicated that ultrasonic cavitation during solidification will greatly improve the microstructure of the samples. Al2O3 and SiC nanoparticle reinforced nanocomposites have different nanoparticle distributions in the matrix.

Potential of an Al-Ti-MgAl2O4 Master Alloy and Ultrasonic Cavitation in the Grain Refinement of a Cast Aluminum Alloy

A new grain refining master alloy containing MgAl2O4 and Ti was synthesized by in situ reaction of TiO2 particles in an Al-Mg melt. MgAl2O4 particles formed were distributed in the melt by ultrasonic cavitation processing. The obtained master alloy showed considerable (50 pct) grain refining ability in a commercial A357-type Al-Si alloy. Ultrasonication contributed further to 25 pct in the grain refinement. In comparison with a commercial Al-5 pct Ti-1 pct B master alloy, the efficiency of the new master alloy is less at a lower addition rate. Nevertheless, both master alloys performed similarly at higher additions. The strength and ductility of the inoculated and ultrasonicated alloy showed at least a 10 pct and a 50 pct increase, respectively, as compared with non-grain-refined alloy and a similar mechanical performance in comparison with the alloy inoculated with Al-5 pct Ti-1 pct B master alloy.

Preparation of SiC based Aluminium metal matrix nano composites by high intensity ultrasonic cavitation process and evaluation of mechanical and tribological properties

Request augments on a worldwide scale for the new materials. The metal matrix nano composites can be used in numerous applications of helicopter structural parts, gas turbine exit guide vane's, space shuttle, and other structural applications. The key mailman to ameliorate performance of composite matrix in aluminium alloy metal reinforces nano particles in the matrix of alloy uniformly, which ameliorates composite properties without affecting limit of ductility. The ultrasonic assisted stir casting helped agitation was successfully used to fabricate Al 2219 metal matrix of alloy reinforced with (0.5, 1, 1.5 and 2) wt.% of nano silicon carbide (SiC) particles of different sizes 50nm and 150nm. The micrographs of scanning electron microscopy of nano composite were investigated it reveals that the uniform dispersion of nano particles silicon carbide in aluminium alloy 2219 matrix and with the low porosity. How the specific wear rate was vary with increasing weight percentage of nano particles at constant load and speed as shown in results and discussions. And the mechanical properties showed that the ultimate tensile strength and hardness of metal matrix nano composite AA 2219 / nano SiC of 50nm and 150nm lean to augment with increase weight percentage of silicon carbide content in the matrix alloy.

Analysis methods of determining velocity distribution waves in the cavitation zone ultrasound field

The main parameters of cavitation processing technology environments is the speed of sound in a cavitation medium pressure, the duration, size: cavitation region, bubbles and core. The most successful use of ultrasound associated with handling liquid media, because in them the phenomenon of ultrasonic cavitation, which is an effective mechanism for concentration of energy of sound waves in the low-density high energy density, which is caused by pulsations and cavitation bubbles popping. An important component in ensuring an effective process of cavitation treatment process fluids is to calculate the ultrasonic technological devices that hold for precavitational mode with the following specification obtained by previous studies. However, reliable results associated with the methods of measuring the velocity of ultrasonic waves in a developed cavitation because it is a part of almost all the defining parameters of ultrasonic cavitation processing technology environments. Measuring the velocity of ultrasonic waves carried pulse, optical, amplitude-phase methods. Pulse methods have a wider dynamic range, measurement accuracy independent of the distance between the transmitter and the object opportunity emitter distance from the subject a considerable distance. Amplitude-phase methods require extended frequency band transceiver emitting element and amplifier path that reduces security and selectivity. Frequency and phase methods have the narrow bandwidth receiving radiating path that provides good value energy radiated and received signals, high noise immunity. Is an effective method for determining the rate for power characteristics, the essence of which is to determine the energy flux density and energy density relative to the ultrasound field. It has been found that the accuracy of measuring the speed of sound depends on whether it should receive the absolute value or relative value can restrict the speed of sound when changing any external parameters. Absolute measurement accuracy is about 10-5, while the relative change as accuracy is much higher, it reaches the order of 10-7. The choice of measurement due to the conditions of the experiment. The essential difference in the numerical values of the speed, complicates the acceptance of an opinion on the actual numerical value of speed and requires more informed research in determining the accepted assumptions and preconditions in the formulation and conduct research.

Optimisation on pretreatment of kapok seed (Ceiba pentandra) oil via esterification reaction in an ultrasonic cavitation reactor

Pretreatment of the kapok seed oil via esterification reaction has been investigated by using an ultrasonic cavitation reactor. Reaction parameters have been optimised by using response surface methodology and found as methanol to oil ratio of 16.23:1, catalyst amount of 9.94 wt% and reaction time of 20.08 min at amplitude of 32.04 %. The significance of the reaction parameters toward free fatty acid reduction was in the order of amplitude > reaction time > molar ration of methanol to oil > catalyst amount. The reaction time and esterified efficiency of ultrasonic cavitation was 4.5-fold shorter and 10.5-fold higher than mechanical stirring. The reactant used per produced biodiesel in ultrasonic cavitation process was about 2.6 lower compared to mechanical stirring process.

An experimental and modeling investigation of aluminum-based alloys and nanocomposites processed by ultrasonic cavitation processing

Some recent studies are showing that the microstructure and mechanical properties of manufactured components can be significantly improved when ceramic nanoparticles are used as reinforcement to form a metal-matrix-nano-composite (MMNC). During the fabrication of MMNCs, ultrasonic cavitation processing plays an important role in refining microstructure, dispersing nanoparticles and breaking up clusters of nanoparticles.In the present study, aluminum A356 alloy and Al2O3/SiC nanoparticles are used as the matrix alloy and the reinforcements, respectively. Nanoparticles are injected into the molten alloy and dispersed by ultrasonic cavitation and acoustic streaming. The microstructure and mechanical properties of the cast nanocomposites have been investigated in detail.

Advanced Numerical Modeling of the Dispersion of Ceramic Nanoparticles during Ultrasonic Cavitation Processing and Solidification of 6061-based Nanocomposites

The metal-matrix-nano-composites (MMNCs) in this study consist of a 6061 alloy matrix reinforced with 1.0 wt.% SiC 50 nm diameter nanoparticles that are dispersed uniformly within the matrix in large volume using an ultrasonic cavitation dispersion technique (UCDS) available in the Solidification Laboratory at UA. The required ultrasonic parameters to achieve the required cavitation for adequate degassing and refining of the aluminium alloy as well as the fluid flow characteristics for uniform dispersion of the nanoparticles into the 6061 matrix are being investigated in this study by using an in-house developed CFD ultrasonic cavitation model. The multiphase CFD model accounts for turbulent fluid flow, heat transfer and solidification as well as the complex interaction between the solidifying alloy and nanoparticles by using the Ansys's Fluent Dense Discrete Phase Model (DDPM) and a particle engulfment and pushing (PEP) model. The PEP model accounts for the Brownian motion. SEM analysis was performed on the as-cast MMNC coupons processed via UCDS and confirmed the distribution of the nanoparticles predicted by the current CFD model. A parametric study was performed using the validated CFD model. The study includes the effects of magnitude of the fluid flow and ultrasonic probe location (gravity direction).

Preparation of SiC Nano-particulates Reinforced Aluminum Matrix Nanocomposites by High Intensity Ultrasonic Cavitation Process

The present investigation attempts to evaluate the effect of high intensity ultrasonic cavitation on dispersing the SiC nanoparticles in aluminum 6061 melt. Aluminum melt with various volume percentages of SiC nanoparticles was ultrasonically processed by dipping the ultrasonic horn into the melt. SEM and EDS study with elemental mapping validates the uniform distribution of SiC nanoparticles in the Al matrix. Compared to the un-reinforced alloy matrix and conventional composites, the mechanical properties of the nanocomposites, including tensile strength and hardness improved quite significantly as the particle volume percentage increased. The nanocomposites show better ductile properties as compared to the conventional composites. To understand the effect of ultrasonic vibrations on processing the nanocomposites, the nanocomposite was processed at three amplitudes and the results are presented. Ultrasonic cavitation based fabrication process proved as a better alternative to the conventional stir casting route to disperse the nano ceramic particles in molten alloys.

Power spectrum of fluctuation for ultrasonic cavitation process in glycerin

Experiments were carried out on ultrasonic cavitation in glycerin. The zone near the emitter has a structure from interacting gas-vapor bubbles; this structure takes the form of fractal clusters. The photometry of passed laser emission was the tool for studying dynamics of fluctuations. In transitive mode, the power spectrum of fluctuation varies by the law inversely proportional to frequency. Distributions of local fluctuations are different from Gaussian and exhibit the property of scale invariance. The qualitative behavior of the frequency dependence of the spectral fluctuation density was tested while varying the power of the ultrasonic emitter. It was demonstrated that the growth of the high-frequency margin of flicker-type behavior evidences for growing instability and can be considered as a forerunner of possible large-scale outbursts.

Response of sandwich composites with nanophased cores under flexural loading

It is well known that in a sandwich structure, the core plays an important role in enhancing the flexural rigidity and by controlling the failure mechanisms. If the core is made from foam, the strength of the core material and the debond strength at the core–skin interface almost entirely dictate the performance of structural sandwich composites especially under flexure. In this investigation attempts have been made to improve the performance of the sandwich by strengthening the core but partially sacrificing the debond fracture toughness of the sandwich construction. Strengthening of the core has been accomplished by infusing nanoparticles into the parent polymer of the core material when it was in the liquid stage. The core material is polyurethane foam made from polymeric isocyanate (Part A) and reacting with polyol (Part B). Spherical nanoparticles such as TiO 2 of about 29 nm in diameters were dispersed in Part A of liquid polyurethane through an ultrasonic cavitation process. The amount of nanoparticles infused into liquid foam varied from 1 to 3% by weight. Once Part A was doped with nanoparticles, it was mixed with Part B, and was cast in a rectangular mold to produce the nanophased polyurethane foam. The nanophased foam was then used with regular S-2 Glass fiber preforms and SC-15 epoxy to manufacture sandwich composites in a VARTM set up. Test coupons were then extracted from foam as well as from sandwich panels to conduct flexural and various other chemical tests. A parallel set of control panels were also made with neat polyurethane core materials. Thermogravimetric and SEM analyses have indicated that the decomposition temperature of the nanophased foams increases by about 27 °C and the cell size almost doubles with nanoparticle infusion. A significant improvement in flexural strength and stiffness has also been observed with 3% loading of TiO 2 nanoparticles. Debond fracture toughness parameters ( G c) were also determined for both categories of sandwich constructions, and it was seen that nanoparticle infusion reduces the value of G c by almost a factor of three. Despite this reduction, strength of nanophased sandwich increased by about 53% over the neat system. Details of manufacturing and analyses of test results are included in the paper.