High-temperature mechanical behavior of Ti-6Al-4V alloy and TiC p /Ti-6Al-4V composite
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I. INTRODUCTION
METAL matrix composites (MMCs) are being considered for structural applications where potential weight-savings can be realized using light-weight matrices strengthened by strong ceramic phases. TiC-reinforced titanium matrix composites are particularly attractive because of their very high specific moduli and specific strengths of both the matrix and the reinforcing phase. Most of the research work is concentrated on continuous fiber-reinforced Ti composites (especially SCS-6 fiber-reinforced MMCs[1–5]). However, these composites are highly anisotropic in properties, and their fabrication is complex and expensive. Interest has increased in ceramic particulate-reinforced Ti matrix composites in recent years, because these composites have isotropic characteristics and can be processed inexpensively using conventional technologies, such as ingot metallurgy, casting, and powder metallurgy (P/M). Also, they can be tailored to give improved strength, stiffness, hardness, abrasion resistance, and dimensional stability over conventional titanium alloys. Despite recent advances in the processing and manufacturing technology of TiC particulate-reinforced Ti MMCs (designated as TiCp /Ti in the following text),[6,7,8] there is a lack of a systematic understanding of the mechanical behavior of these materials at elevated temperatures. Tensile properties of TiCp /Ti composites prepared by casting, conventional J.H. ZHU, formerly Graduate Student, Department of Materials Science and Engineering, The University of Tennessee, is Postdoctoral Research Associate, Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6115. P.K. LIAW, Professor and Ivan Racheff Chair of Excellence, is with the Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996-2200. J.M. CORUM, Corporate Fellow, and H.E. McCOY, JR., Staff Member, are with the Engineering Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-8051. Manuscript submitted May 20, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
P/M, and blended elemental P/M routes were reported in References 9 through 11. Also, Shang and co-workers[12,13,14] have studied the temperature dependence of the fracture toughness and fatigue crack growth resistance in P/M TiCp / Ti MMCs. However, the effect of strain rate on the tensile behavior of TiCp /Ti-6Al-4V MMCs has not been investigated, and creep characteristics of the composite have not been examined so far, while such mechanical properties are essential for the design and application of TiCp /Ti components subjected to elevated-temperature environments. In the present article, recent results are provided on the high-temperature mechanical behavior, microstructural characterization, and damage mechanisms of both the Ti-6Al4V alloy and the associated composite.
II. EXPERIMENTAL The materials used in this investigation were the baseline Ti-6Al-4V (wt pct) alloy and the Ti-6Al-4V matrix composite reinforced with 10 wt pct TiC particulates (TiCp /T
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