Design and fabrication of W-Mo-Ti-TiAl-Al system functionally graded material
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I. INTRODUCTION
SINCE the concept of functionally graded materials (FGMs) was proposed, a great deal of research work on such a kind of advanced material has been done worldwide for different applications. Recently, FGMs have come to show high potential for application in dynamic high-pressure technology. The shock-loading technique is an important way to study the mechanical characteristics of materials at high pressure and temperature. It is characterized by a short duration and great interior dissipation effect and causes a great temperature rise in materials. The mechanical parameters of materials under shock loading, such as shear modulus (G) and bulk modulus (K ), are affected simultaneously by pressure and temperature. The great temperature rise in materials makes it difficult to compress them even more. Researchers[1,2] commenced the study of quasi-isentropic loading in the 1980s. Quasi-isentropic loading is a kind of compression wave with a smoothly increasing front, that is, the samples are loaded step by step and the temperature rise in materials is small, which is markedly different from general shock loading. It can provide a greater compression compared to shock loading when compressing the same volume.[3] In this case, the mechanical parameters are mainly affected by pressure, so the contributions of temperature and HUAPING XIONG is with the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, People’s Republic of China, and concurrently with the Welding and Forging Lab, Beijing Institute of Aeronautical Materials, Beijing 100095, People’s Republic of China. LIANMENG ZHANG is with the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, and concurrently with the Institute for Materials Research, Tohoku University, Sendai 980-77, Japan. LIDONG CHEN and TOSHIO HIRAI are with the Institute for Materials Research, Tohoku University. RUNZHANG YUAN is with the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology. Manuscript submitted November 3, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
pressure to the mechanical parameters can be separated,[4] and this is important for studying the constitutive relation at high pressure. According to the literature,[5,6] quasi-isentropic loading can be obtained by using graded-density flyers. Recently, the application of graded-density layered materials in highpressure technology has been reported.[7] However, they were only fabricated by bonding a series of thin plates such as Ta, Cu, Ti, Al, Mg, and TPX (a plastic with a density of 0.81 g/cm3); thus, the density of the layered materials rises with several distinct steps in the thickness direction. It is expected that a better effect would be achieved[8] by using a graded material with a continuous or quasi-continuous density change. Moreover, a graded material with a wide density range is desirable; namely, the den
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