Mechanical Behavior of Ternary and Quaternary Rual Alloys
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MECHANICAL BEHAVIOR OF TERNARY AND QUATERNARY RuAl ALLOYS T. K. Nandy1 , Q. Feng1 , D. Banerjee2 , M. F. X. Gigliotti3 , T. M. Pollock1 1
University of Michigan, Materials Science and Engineering, Ann Arbor, MI 48109 USA. Defense Metallurgical Research Lab., Hyderabad 500058, India. 3 General Electric Company, Corporate Research and Development, Schenectady, NY 12301 USA. 2
Abstract The mechanical behavior of RuAl-base intermetallic alloys with alloying additions of boron, niobium and platinum has been investigated. Compression tests have been performed at room temperature and 973 K. While the addition of alloying elements results in solid solution strengthening, the strain-rate sensitivity and the activation volumes do not show a significant variation, thereby suggesting that the macroscopic flow mechanisms are not strongly affected. Deformation substructure analysis of the niobium-containing alloy shows the presence of and dislocations, while the platinum-containing alloy additionally contains a significant density of dislocations. Introduction High temperature intermetallics have been the subject of intensive research investigation as the search for new high temperature materials for high performance, efficient aerospace gas turbine engine continues. A survey of large number of very high temperature intermetallics (Tm > 1973 °K) carried out by Fleischer and coworkers [1, 2] indicated four binary systems with promising room temperature and elevated mechanical properties: IrNb (L1 0, tP4 space group), RuTa (L1 0 ), RuSc (B2, cP2 space group) and RuAl (B2). Of these, RuAl and RuTa are considerably less expensive. RuAl, in particular, exhibits high compressional plasticity and good oxidation resistance [3]. Therefore, studies have been carried out to understand and improve mechanical properties of alloys based on this intermetallic. Fleischer and coworkers [3-7] studied the effect of different alloying additions such as Ti, Co, Fe, Sc, Cr, Y, Si, Re and B on solid solution strengthening and compressional ductility. Additions of scandium and boron were found to be beneficial. Subsequently, Wolff and Sauthoff [8] studied the effect of microstructure and showed a beneficial effect of a compliant grain boundary layer on room temperature mechanical properties. A detailed mechanical behavior study on RuAl containing boron was carried out by Pollock and co-workers [9-12]. In this study, deformation was shown to occur by glide of and dislocations on close packed {110} planes, giving rise to five independent slip systems (required for ductility in polycrystalline specimens). This mode of deformation was observed over a temperature range of 77-1023 K. Also, low temperature deformation was characterized by lower rate sensitivities that suggested a relatively high intrinsic mobility of the dislocations, compared to other high temperature B2 intermetallics. It should be emphasized that no detailed studies of this intermetallic have yet been conducted under tensile loading conditions, due to the fact that bulk material
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