A Developed Method for Fabricating In-Situ TiC p /Mg Composites by Using Quick Preheating Treatment and Ultrasonic Vibration Z.W. LIU, M. RAKITA, Q. HAN, and J.G. LI 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 Al 3 Ti 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 lm 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 syn- thesize in-situ TiC p /Mg composites is proposed in our research. DOI: 10.1007/s11661-011-1041-0 Ó The Minerals, Metals & Materials Society and ASM International 2012 I. INTRODUCTION PARTICULATE reinforced magnesium composites have attracted considerable attention in the aerospace and automobile industries due to their lightweight and good mechanical properties. [1–4] Generally,the fabrica- tion of in-situ TiC p /Mg composites by using Al-Ti-C as a reactive system has been studied widely. In the conven- tional methods, Al-Ti-C is added into the molten magnesium and ignited by the heat of magnesium melt. In-situ TiC particles are synthesized by the thermal explosion reaction of Al-Ti-C. In addition, mechanical stirring is usually used to disperse the TiC particles into the magnesium matrix. [5,6] The time from the addition of Al-Ti-C to the occurrence of the thermal explosion reaction in the molten magnesium is called the delay time. Long delay time usually results in the nonoccurrence of the final reactions of Al-Ti-C in the molten magnesium. The solid aluminum powders easily get dissolved into the magne- sium melt, making the Al-Ti-C pellet incompact due to the long delay time. As a result, some unreacted carbon powders float on the surface of the magnesium melt, and some titanium powders deposit at the bottom of the crucible. The preheating treatment of Al-Ti-C is the key to decreasing the delay time in the fabrication of in-situ TiC p /Mg composites. In the conventional meth- ods, [6,7] Al-Ti-C is preheated outside of the furnace in which magnesium is melted before adding it into the matrix. Extra heating equipment is needed, and com- plicated preheating conditions are demanded as well. On the one hand, the preheating temperature should be in the range of 623 to 873 K (350 to 600 °C). Al-Ti-C without preheating treatment or with low preheating temperatureis not able to give rise to reaction to form TiC phase in the molten magnesium at 1023 K (750 °C). A preheating temperature higher than 873 K (600 °C) is not available, because Al-Ti-C can be ignited easily at 873 K (600 °C) before adding it into the molten magnesium by using the conventional methods.On the other hand, the preheating time usually lasts at least 60 minutes. Mechanical stirring is the most widely used method to disperse the reinforced particles in the fabrication of particulate reinforced aluminum matrix compos- ites. [8,9] However, some severe issues such as clustering, high porosity, and oxide inclusions usually associate with the mechanical stirring. Ultrasonic vibration can solve the preceding issues effectively, and the related work was reported in our former work. [10] Little work was reported to introduce ultrasonic vibration in the fabrication of in-situ TiC p /Mg composites. In our research, the conventional Al-Ti-C was used and the temperature of molten magnesium was chosen at 1023 K (750 °C). A novel quick preheating treatment of Al-Ti-C was designedby means of preheating Al-Ti-C in the furnace in which magnesium was melted as well. In addition, high-intensity ultrasonic vibration was Z.W. LIU, Postdoctoral Candidate, and J.G. LI, Professor, are with the School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200240, P.R. China. M. RAKITA, Postdoctoral Candidate, and Q. HAN, Professor, are with the Department of Mechanical Engineering Technology, Purdue University, West Lafay- ette, IN 47906. Contact e-mail: hanq@purdue.edu Manuscript submitted June 16, 2011. Article published online February 10, 2012 2116—VOLUME 43A, JUNE 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A