Effect of Ultrasonic Vibration on Direct Reaction Between Solid Ti Powders and Liquid Al
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vious research,[1] we discussed the formation mechanism of small blocky in-situ Al3Ti particles via direct reaction between solid Ti powders and liquid Al. A related reaction-peeling model was applied to illustrate the reaction process of solid Ti in the liquid Al, which involved in the following process: the nucleation of Al3Ti, the growth of Al3Ti, and the rupture of Al3Ti. As a result, a simple method for fabricating in situ Al3Ti/Al composites was proposed. How to decrease the size of in situ-formed Al3Ti particles further has become a new interesting research topic for us. Ultrasonic vibration has been extensively used in the purifying, degassing, and the refinement of metallic melt,[2,3] as well as the fabrication of in situ particulatereinforced metal matrix composites,[4,5] as the injection of ultrasonic fields in a liquid can give rise to nonlinear effects, such as cavitation, acoustic streaming, and high local pressure.[6]
Z.W. LIU, Ph.D. Student, X.M. WANG, Visiting Assistant Professor, and Q.Y. HAN, Professor, are with the Department of Mechanical Engineering Technology, Purdue University, 401 North Grant Street, West Lafayette, IN 47906. Contact e-mail: [email protected], [email protected] J.G. LI, Professor, is with the School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, P.R. China. Manuscript submitted July 20, 2013. Article published online December 13, 2013 METALLURGICAL AND MATERIALS TRANSACTIONS A
Some related study has demonstrated that highintensity ultrasonic vibration can break up the clusters of reinforced particles in the matrix. Specially, long rodlike Al3Ti particles can be broken into small blocky ones in the ultrasonic fields.[7–9] However, very little research has been reported on the effect of ultrasonic vibration on the direct reaction between solid Ti and liquid Al. In the current research, the evolution of solid Ti powders in the liquid Al in the ultrasonic fields was investigated, which also can be regarded as a continuation of our former study.[1] Pure aluminum (99.5 pct commercial purity) ingot and titanium powders (99.7 pct purity, 40 lm) were used as the matrix and additive, respectively. Titanium powders wrapped in aluminum foil were added into the aluminum melt at 1003 K (730 °C). In the meantime, high-intensity ultrasonic vibration was introduced into the melt by immersing the Nb radiator into the melt. The schematic illustration is shown in Figure 1. The power of the ultrasonic generator was 1.5 kW, and the frequency was 20 kHz. After ultrasonic treatment for 5 minutes, the melt was poured into the steel mold to form an ingot. The ultrasonic-treated sample and the contrast sample without ultrasonic treatment are named Sample UV730 and Sample 730, respectively. The phase formed during the fabrication was examined by X-ray diffraction (XRD, Bruker D8, Bruker AXS, Karlsruhe, Germany) using Cu Ka radiation at 40 kV and 40 mA and a scan rate of 0.015 deg/s. The microstructural features of the sample were examined by scanning electron microscopy (S
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