High-intensity Ultrasonic Vibration Research Articles

Grain refinement and Laves phase dispersion by high-intensity ultrasonic vibration in laser cladding of Inconel 718

Laser cladding is a promising surface modification and repair technology for fabricating Inconel 718 parts. However, laser cladding may produce coarse grains and brittle Laves phase, leading to a significant decrease in performance. The application of high-intensity ultrasonic vibration in laser cladding is able to refine grain and reduce Laves phase. This study investigates the distribution characteristics and the evolution mechanism of the grains and Laves phase in laser cladding with high-intensity ultrasonic vibration. The effects of high-intensity ultrasonic vibration on alteration of grain characteristics and the reduction of Laves phase were analyzed and discussed through ultrasonic vibration-assisted laser cladding experiments. Results indicate that high-intensity ultrasonic vibration promoted a columnar-to-equiaxed transition, and reduced the grain size from 75.6 μm to 48.8 μm. Furthermore, the Laves phase had a decrease of 47.1% in the volume fraction, and transformed from a long-striped shape into a fine granular shape, leading to a more homogeneous distribution of elements in Laves phase. The change in the grains and the Laves phase is attributed to dendrite fragmentation and inhibition of element segregation by nonlinear effects of ultrasound including cavitation and acoustic streaming. The findings of this study confirm the significant benefits of applying high-intensity ultrasonic vibration in laser cladding and provide insight into the underlying evolution mechanisms of high-intensity ultrasonic vibration for grains and Laves phase.

Effects of ultrasonic vibration on microstructure and mechanical properties of 1Cr12Ni3MoVN alloy fabricated by directed energy deposition

Due to the rapid melting and solidification during directed energy deposition (DED) process, the defects and columnar crystals are likely to generate in the deposition layers, which reduce the quality and performance of the whole parts. Therefore, in order to improve the microstructure and mechanical properties of 1Cr12Ni3MoVN alloy manufactured by DED method, ultrasonic vibration (UV) has been employed to assist directed energy deposition process in this work. The results indicate that the high-intensity ultrasonic vibration can weaken the epitaxy growth tendency of crystal grains, and significantly improve plasticity while keeping an approximate strength. In addition, a two-dimensional numerical model is established to simulate the effect of ultrasonic vibration in the molten pool. The simulation results show that ultrasonic vibration remarkably improves the flow velocity and pressure in the molten pool, inducing the cavitation effect that breaks dendritic crystal and affects crystal characteristics. Meanwhile, the acoustic streaming effect changes the thermodynamic conditions and promotes high-temperature diffusion, which uniforms temperature distribution and reduces the temperature gradient in the molten pool. Thus the reduced temperature gradient G and raised solidification growth rate R promote the formation of fine equiaxed crystal characteristics after UV treatment. The product G × R increases and the ratio G/R decreases after UV treatment, resulting in the formation of fine equiaxed crystals.

Influence of ultrasonic vibration on molten pool behavior and deposition layer forming morphology for wire and arc additive manufacturing

Ultrasonic assisted metal additive manufacturing is a promising technology with the ability of changing the forming appearance and improving the mechanical properties. To study the influence of assisted ultrasonic vibration (UV) on molten pool behavior and deposition layer forming morphology of wire and arc additive manufacturing (WAAM) parts, a three-dimensional CFD numerical model of the WAAM process with the UV was established, and deposition experiments were carried out. The effect of ultrasonic on pressure field, temperature field and fluid flow in molten pool and appearance of deposition layer were explored. The results showed that assisted high-intensity ultrasonic vibration can significantly change the frequency and amplitude of pressure in molten pool, the cavitation effect strongly affected the grain morphology and size of the deposition layer. The acoustic streaming promoted the flow rate and high-temperature diffusion, which resulted in more uniform temperature distribution and reduced temperature gradient. In addition, many capillary waves appeared on the surface of the molten pool indicating that the surface state of molten pool was also obviously changed by ultrasonic vibration. With the improvement of the wettability and spreading of molten pool by ultrasonic, the width of the deposition layer increased while the height and depth decreased, but the cross section area of deposition layer remained the same. These findings demonstrate the mechanisms of how ultrasonic wave changes the behavior of molten pool and morphology of deposition layer, lay the foundation for further research on performance and morphology control of ultrasonic assisted WAAM.

The Influence of High Temperature Ultrasonic Processing Time on the Microstructure and Mechanical Properties AZ91E Magnesium Alloy

The reduction of harmful greenhouse gas emissions can be realized by utilizing lightweight structural metals, such as magnesium (Mg). Magnesium alloys have the potential to replace higher-density aluminum and ferrous components in automotive and aerospace industries, thereby decreasing vehicle weight and the associated fuel requirements. However, their strength and ductility must be improved to ensure widespread application. This goal can be achieved through ultrasonic processing, a technique that is gaining popularity in the manufacturing of light alloys. In this study, the effects of high-intensity ultrasonic vibration on the microstructure and mechanical properties of AZ91E were investigated. The molten alloys were subjected to 60, 120, 180 and 240 s of sonication at a frequency and amplitude of 20 kHz and 30 µm, respectively. The resultant castings were characterized using optical microscopy, scanning electron microscopy and tensile testing. Sonication was found to improve the mechanical properties of the alloy relative to the base condition. The improvement was attributed to the refinement of the Mg grain structure, decreased area fraction and average size of the brittle Mg17Al12 eutectic phase, in addition to increased area fraction, homogenous distribution and spheroidization of the Mn-Al intermetallic phase. The refinement in microstructure was determined to be a result of improved nucleation and cavitation-induced undercooling of the melt as well as a finer grain size. Therefore, ultrasonic processing can enhance the viability of Mg alloys as engineering materials, offering important opportunities for the production of greener, light-metal components.

Ultrasonic Processing of Magnesium Alloy for Property Enhancement

The reduction of harmful greenhouse gas (GHG) emissions can be realized by utilizing lightweight structural metals, such as magnesium. Magnesium alloys have the potential to replace higher-density aluminum and ferrous components in automotive and aerospace industries, thereby decreasing vehicle weight and the associated fuel requirements. However, their strength and ductility must be improved to ensure widespread application. This goal can be achieved through ultrasonic processing in the molten state, a technique that is gaining popularity in the manufacturing of light alloys. In this study, the effects of high-intensity ultrasonic vibration on the microstructure and hardness of AZ91E Mg alloy was investigated. The molten alloys were subjected to sonication of varying durations, and the resulting castings were characterized using optical microscopy, scanning electron microscopy and hardness testing. Sonication was found to successfully increase the hardness of the alloy relative to the base condition. This improvement was attributed to the refinement of the magnesium grain structure as well as the Mg17Al12 and Mn-Al secondary phases in the sonicated alloys. The competitiveness of magnesium alloys can be significantly enhanced via ultrasonic processing, offering important opportunities for the production of greener, light metal components.

Achieving high stability of MgO/carbon nanotube interface via the co-deposition technique

In this work, high stability of MgO/carbon nanotube (CNT) interface has been achieved through coating MgO nanoparticles on the surface of CNT via the co-deposition technique. Experimental results indicate that two types of MgO nanoparticles, those are single-crystal and poly-crystal nanoparticles were uniformly coated on the surface of CNT. The oxygen groups on CNT introduced by purification are crucial to the nucleation and growth of MgO nanoparticles on the surface of CNT via the C–O–Mg bonds interaction, and resulting in the formation of MgO/CNT interface in the sample of MgO@CNT. The survived stable interface of MgO/CNT in the long time (22 h) and high intensity ultrasonic vibration (1000 W) treatment, suggests that the MgO/CNT interface has an excellent stability in microstructure. The calculations of work of adhesion for the interface models gives the evidence that MgO nanoparticles can form a strong interfacial bonding with CNT, proving the high stability of the MgO/CNT interface. MgO-coated CNT with high stable interface is suited to act as the reinforcing additive for the matrix of Mg alloy.

Degassing of Pure Copper Melt by Ultrasonic Cavitation

The effect of high intensity ultrasonic vibration (UV) on degassing of pure copper has been studied in this paper. The methods of reduced pressure test (RPT) and direct hydrogen and oxygen measurements are used for the evaluation of degassing efficiency on hydrogen and oxygen concentrations. The results showed that high intensity UV had a significant degassing effect for the commercially pure copper (CP-Cu) melt. With UV, the density index Di was reduced from 11.94 to 1.13%, and the product of hydrogen-oxygen concentration ([%H]·[%O]) in the liquid Cu was decreased to 1.440×10−5 from 6.624×10−5. It was also found that electric power and ultrasonic treatment time could influence the degassing efficiency.

Fabrication of Carbon Nanofibers/A356 Nanocomposites by High-Intensity Ultrasonic Processing

A356 alloy reinforced with carbon nanofibers (CNFs) was fabricated by high-intensity ultrasonic vibration processing. The microstructure and mechanical properties were investigated. The distribution of CNFs became more and more uniform with the increase of ultrasonic power, and the mechanical properties of nanocomposites were significantly enhanced accordingly. The yield strength (YS), ultimate tensile strength (UTS), and microhardness of the nanocomposite increased by 38.3, 21.9, and 43.2 pct, respectively, at a CNF content of 0.9 wt pct compared with the matrix without CNF addition. The improvement in mechanical properties was the effect of CNFs on the thermal expansion mismatch strengthening of the nanocomposite, the grain refinement of the nanocomposite, and the load transfer from the matrix to the nanofibers.

Effect of ultrasonic vibration on microstructural evolution and mechanical properties of underwater wet welding joint

The propagation of high-intensity ultrasonic vibration into weld pool can influence on microstructure and mechanical properties of welded joints. This research introduced a hybrid method for improving weld quality by using superimposed ultrasonic vibration on workpiece directly in underwater flux cored arc welding (FCAW). With the purpose of revealing how macrostructure, microstructure and mechanical properties of welded joints are affected by ultrasonic vibration within the weld metal, the present study has been carried out. The results indicated that proeutectoid ferrite, ferrite side plate and acicular ferrite constitute the microstructures of weld metal. Ultrasonic vibration can affect the size and morphology of prior austenite grain during weld pool solidification and eventually accelerate the formation of fine ferrite microstructure of weld metal in high proportion in the subsequently solid-state phase transformation. Excellent balance of high tensile strength and impact toughness is realized as more fine columnar microstructures in weld metal with using ultrasonic vibration. These findings suggest that the addition of ultrasonic vibration is an effective way to improve the tensile strength and impact toughness of weld metal during underwater wet welding.

Effect of initial Ti powders size on the microstructures and mechanical properties of Al3Ti/2024 Al composites prepared by ultrasonic assisted in-situ casting

In this work, high-intensity ultrasonic vibration was employed in in-situ casting of aluminum matrix composites. In-situ Al3Ti/2024 Al composites with ideal microstructures and mechanical properties were successfully fabricated. The effect of Ti powder sizes on in-situ reaction, microstructures and mechanical properties of Al3Ti/Al composites were studied. The results show that the morphologies of Al3Ti particles and α-Al matrix are dominated by the original Ti powders. When the added Ti powders are too large (e.g. 60 μm and 40 μm) or too small (e.g. 10 μm), some agglomerated Al3Ti particles or blocks existed in the α-Al matrix. However, when the average size of added Ti powders is 20 μm, fine Al3Ti particles were formed and evenly distributed in the α-Al matrix. The refining mechanism of α-Al matrix was also discussed. The composites are significantly strengthened due to ultrasonic vibration and evenly distributed Al3Ti particles. The yield strength, ultimate tensile strength and elongation to fracture are 361 MPa, 449 MPa and 3.16%, respectively. The thermoplastic formability of in-situ Al3Ti/2024Al composites is similar with 2024 alloy.

The effect of combining high-intensity ultrasonic vibration with ECAE process on the process parameters and mechanical properties and microstructure of aluminum 1050

Equal channel angular extrusion, as one most common severe plastic deformation method for producing ultra-fine grain materials, has some limitations such as high forming load, high friction forces, microstructure inhomogeneity, and a large number of passes required for obtaining fine-grained structure. The main goal of this research is investigation on the effect of using high-intensity ultrasonic vibration directly in the plastic deformation zone during the ECAE process of commercially pure aluminum 1050 to improve process limitations. By combining ultrasonic vibration with the ECAE, the sample with nearly equiaxed grains and average size ∼2 μm was achieved just after one pass more effective than two passes of conventional ECAE via routes C and Bc. Accordingly, the samples with 22 % higher hardness, 10 % more compressive strength, and also 30 % lower required forming load were attained during ultrasonic-assisted ECAE with applied vibration amplitude 15 μm.

Effects of ultrasonic vibration on the microstructure and tensile properties of the nano ZrB2/2024Al composites synthesized by direct melt reaction

In this study, the effects of high-energy ultrasonic vibration on the dispersion of in situ nano-sized reinforcements were studied in nano ZrB2 particle reinforced 2024Al matrix composites synthesized from 2024Al–K2ZrF6–KBF4 system by direct melt reaction. And the microstructure of the final composites treated with different processing time of ultrasonic vibration during fabrication was examined by XRD, SEM, EDS, TEM and the tensile properties of the fabricated composites were also tested. The results show that the introduction of high-energy ultrasonic vibration in the composite melts could break up the clusters of agglomerated in situ nano ZrB2, degas the melts, significantly and results in enhancement in mechanical properties of the final composites. And the optimized processing time for the fabrication of the nano ZrB2/2024Al composites was established via the microstructure observation of the final composites to be 5 min with 1.2 kW in power and 20 kHz in frequency. Meanwhile, the mechanisms of the high-intensity ultrasonic vibration on the improvement of the in situ nanoparticle distribution and tensile properties of the composites were also discussed.

Ultrasonic assisted equal channel angular extrusion (UAE) as a novel hybrid method for continuous production of ultra-fine grained metals

The propagation of high-intensity ultrasonic vibration (UV) into metals can influence on mechanical and microstructure properties. The main objective of this research is to introduce a new hybrid method for improving limitations of the conventional equal channel angular extrusion (CECAE) process by using superimposed ultrasonic vibration on billet in the plastic deformation zone (PDZ) directly. The experimental set-up was designed and fabricated for the UAE process of commercially pure aluminum (99.5%) with two distinct wave propagation directions as laterally (L-UAE) or vertically (V-UAE). By combining of high-intensity UV with the ECAE process, ultra-fine grained (UFG) aluminum with grain size about ~2µm was attained only with one pass, enabling even higher values of microhardness on processed samples. Moreover, the required load with UAE was about 30% lower than CECAE. Finite element simulations further confirmed the more plastic deformation during UAE than CECAE. The use of UV vertically against extrusion direction (V-UAE) showed better homogeneity in strain, grain size and hardness distributions.

Analysis of Temperature Field in a High-Intensity Ultrasonic Chamber

High-intensity ultrasonic vibration in narrow resonators creates various thermal effects, which has turned it in recent years into a promising new technology in ultrasonic power determination, as well as ultrasonic diagnostic and miniaturized thermoacoustic refrigerators. As a new type of thermoacoustic engine, miniature thermoacoustic device research is still in its infancy. The thermal effects in these engines are partly studied by assuming that the mean temperature in these machines does not change. In view of the aforementioned, complete calculations related to the generation, propagation, and temperature stabilization processes of high-intensity ultrasonic waves in a duct were performed, with the intention of providing a comprehensive view of the thermal processes in linear and nonlinear ultrasonic chambers. The mean temperature distributions and the related acoustic streaming patterns were predicted to vary with the increasing driving amplitude. A weak shock wave was generated in the large-amplitude cases. The integrated effects of the hysteresis loss, acoustic streaming, and weak shock led to dramatic variations of the heat flux transferred between the fluid and the isothermal walls in different amplitude acoustic fields. The results could guide the arrangement of measurement points in the determination of ultrasonic power, and they are significant for improving the efficiency of thermoacoustic devices.

Ultrasonic Processing of Materials

Irradiation of high-energy ultrasonic vibration in metals and alloys generates oscillating strain and stress fields in solids, and introduces nonlinear effects such as cavitation, acoustic streaming, and radiation pressure in molten materials. These nonlinear effects can be utilized to assist conventional material processing processes. This article describes recent research at Oak Ridge National Labs and Purdue University on using high-intensity ultrasonic vibrations for degassing molten aluminum, processing particulate-reinforced metal matrix composites, refining metals and alloys during solidification process and welding, and producing bulk nanostructures in solid metals and alloys. Research results suggest that high-intensity ultrasonic vibration is capable of degassing and dispersing small particles in molten alloys, reducing grain size during alloy solidification, and inducing nanostructures in solid metals.

Effects of the addition of Ti powders on the microstructure and mechanical properties of A356 alloy

In the present research, the effects of the addition of Ti powders on the microstructure, especially the morphology and size of α-Al crystals and the mechanical properties of A356 alloy were studied. The experimental process involved that 1.5wt.% and 3.0wt.% of Ti powders were added into the molten A356 alloy at 780°C, respectively. In the meantime, high-intensity ultrasonic vibration was introduced into the melt for 5min for dispersing particles and degassing melt. The microstructures and mechanical properties of samples after T6 heat treatment were investigated, respectively. The results showed that in situ formed Al3Ti particles containing element Si were blocky in morphology, with the size in the range of 2–7μm. With the addition of Ti particles, α-Al crystals of A356 transferred from long columnar dendrite to roughly spherical in morphology, and the size of which decreased obviously as well. Comparing with A356 alloy, the hardness, tensile strength and elongation of A356/3.0 wt.%Ti improved by 24.7%, 42.3% and 29.9%, respectively.

Effect of Ultrasonic Vibration on Direct Reaction Between Solid Ti Powders and Liquid Al

In-situ blocky Al3Ti particles can be synthesized by direct reaction between solid Ti powders and liquid Al in terms of reaction-peeling model. In this research, the effect of high-intensity ultrasonic vibration on the reaction was investigated by means of immersing the ultrasonic radiator in the Al melt at 1003 K (730 °C) during the fabricating process. The results show that the thickness of Al3Ti reaction layers can be decreased to range from 2 to 3 μm, and the sizes of most of Al3Ti particles can be reduced in the ultrasonic fields as well, with the average size ranging from 2 to 3 μm. The two changes are both attributed to the effects of external forces produced in the ultrasonic fields. Thereby, small blocky Al3Ti particles can be peeled off from the reaction layer more quickly, making reaction layers to become thinner and the particles smaller.

Comparison Between Ultrasonic Vibration-Assisted Upsetting and Conventional Upsetting

Ultrasonic vibration has been increasingly applied to metal forming processes due to its beneficial effects on the reduction of the forming force, flow stress, and friction coefficient and on the increase of the forming limit of the sheet metal. In this work, the effect of the ultrasonic vibration on the upsetting has been studied experimentally and numerically. The microstructure of the specimens processed with ultrasonic vibration-assisted upsetting (UAU) and conventional upsetting was characterized. Differences in the forming characteristics between these two methods, in terms of metal flow and forming force, were analyzed. The results of this study indicate that the use of high-intensity ultrasonic vibration can induce severe plastic deformation and improve the grain refinement efficiency. The grains of the specimens processed by the UAU process were refined to 100 to 300 nm. A deformation mechanism of the UAU process was proposed. The grain refinement mechanism was used to explain the reason why ultrasonic vibration can be used to improve the grain refinement efficiency of the upsetting process.

Severe Plastic Deformation of Steel Induced by Ultrasonic Vibrations

High-intensity ultrasonic vibration was focused on the tip of conical steel specimens to induce severe plastic deformation at room temperature. We found, for the first time, that grain size smaller than 200 nm was obtained. Furthermore, the sharp tip of the conical specimen became umbrella-shaped or disk-shaped. The tip size changed from 0.5 mm diameter to a disk about 5 mm diameter, representing a large amount of plastic deformation in the metal at the tip of the conical specimen.

A Developed Method for Fabricating In-Situ TiC p /Mg Composites by Using Quick Preheating Treatment and Ultrasonic Vibration

Quick preheating treatment of the Al-Ti-C pellets and high-intensity ultrasonic vibration are introduced in the fabrication of in-situ TiC p /Mg composites. Al-Ti-C pellets are preheated for about 130 seconds in the furnace at 1023 K (750 °C), in which magnesium is melted as well. In this process, plenty of heat can be accumulated due to the reactive diffusion between liquid aluminum and solid titanium in Al-Ti-C, and a small amount of Al3Ti phase is formed as well. After adding the preheated Al-Ti-C into the molten magnesium, thermal explosion takes place in a few seconds. In the meantime, high-intensity ultrasonic vibration is applied into the melt to disperse in-situ formed TiC particles into the matrix and degas the melt as well. Microstructural characterization indicates that in-situ formed TiC particles are spherical in morphology and smaller than 2 μm in size. Furthermore, a homogeneous microstructure with low porosity of the magnesium composite is obtained due to the effect of ultrasonic vibration. A novel approach using the quick preheating treatment technique and high-intensity ultrasonic vibration to synthesize in-situ TiC p /Mg composites is proposed in our research.