Metallographic Structure and Mechanical Properties in Vanadium Modified Titanium Trialuminides
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METALLOGRAPHIC STRUCTURE AND MECHANICAL PROPERTIES IN VANADIUM MODIFIED TITANIUM TRIALUMINIDES TOHRU TAKAHASHI*, KATUYUKI ENDO*, a), SUSUMU KAIZU**,
b) AND
TADASHI HASEGAWA* * Department of Mechanical Systems Engineering, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, JAPAN ** Graduate School, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, JAPAN a) now with SEIKO EPSON Corp., Okaya, JAPAN b)now with NKK Corp., Kawasaki, JAPAN ABSTRACT Two types of aluminum-titanium-vanadium ternary intermetallic compounds have been prepared by arc melting under argon atmosphere. Their compositions were nominally AI65 Ti25 V1 o and Al 57Ti 2 V21; the numbers represent the molar fractions in mol%. These two alloys stan within the gamma-phase field where the Li 0 face-centered tetragonal structure is produced. Metallographic structure and mechanical properties have been investigated. It is suggested that vanadium addition to titanium aluminides and titanium trialuminides can enhance their strength. INTRODUCTION Nowadays, titanium aluminide intermetallics are widely accepted as potential light-weight heat-resisting materials for aerospace applications in the near future[1,21. The pioneering work to investigate the mechanical properties of titanium aluminides at elevated temperature first appeared in 1950s [3]. More and more experimental information is becoming available[4-1 1]. One of the present authors has recently carried out a systematic study about the creep properties of polycrystalline materials of TiAI single phase in compressive creep tests [5-8]. Basic understanding, however, about the well-known brittleness in an ambient temperature range is not satisfactory enough. The fundamental mechanisms of high-temperature deformation and of creep resistance have not been made clear so far. In order to alleviate the room-temperature brittleness and to improve the mechanical strength of titanium aluminides, many experimental efforts have been made, in which small amounts of third alloying elements are added. It was reported that the third-element alloying with vanadium brought about effective improvement in room temperature ductility of TiAI [4]. If further improvement is achieved by micro- and macroalloying, it can be expected that the merits of TiAI intermetallics as heatresisting materials are fully realized. As far as the present authors know, the wide composition range of the gammaphase field in the aluminum-titanium-vanadium ternary intermetallic alloys has not been fully exploited so far. Concerning the aluminum-titanium-vanadium ternary alloy system, several phase diagrams are available[12-14]. On the other hand, there have been not much data published about the mechanical properties of these ternary intermetallic alloys. Aluminum-titanium-vanadium ternary alloys were mainly developed near the titanium corner as the beta-phase and/or alpha-beta dual-phase titanium alloys for jet engine materials. In contrast with these titanium alloys, the gamma intermetallic pha
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