High Cycle Fatigue of (Fe, Ni, Co) 3 V type alloys
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INTRODUCTION
O R D E R E D alloys of the (Fe, Co, Ni)3V system possess excellent creep strength, good resistance to radiationinduced swelling, and high ductility at room temperature. 1'2'3 In addition, their strength increases with temperature, in contrast to the behavior of conventional alloys. The excellent mechanical properties exhibited by these Llz-type (fcc) ordered alloys has led to their consideration as structural materials for possible applications in fusion reactors or steam turbines. Fatigue data on these alloys have not previously been reported, although previous work on FeCo-2 pct V and Ni3Mn suggested that fatigue resistance of Llz-type ordered alloys at room temperature is high. 4 However, the fatigue resistance of ordered Mg3Cd (DO19 structure) has been reported to be very poor? High cycle fatigue of ordered alloys at elevated temperatures has received even less attention. Gittins 6 tested Cu3Au in high cycle fatigue near the critical ordering temperature, T,., and reported intergranular failure for both ordered and disordered specimens, In view of the importance of fatigue as a failure mechanism in high temperature energy generating systems, this program was designed to provide information on the high cycle fatigue resistance of several ordered (Fe, Co, Ni)3V alloys at temperatures to 850 °C. However, because of the limited supply of materials available for test, this paper is concerned primarily with trends in behavior relative to other high temperature alloys.
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EXPERIMENTAL PROCEDURE
The (Fe, Co, Ni)3V alloys were received in the form of rods from C.T. Liu of Oak Ridge National Laboratory. Compositions are listed in Table I. Three heats of LRO-I, (Co, Fe)3V, were tested: LRO-1-3 and LRO-I-13 were arcmelted and LRO- 1-18 was electron-beam-melted. LRO-23 consists of (Co, Fe)3V with an addition of 0.4 pct Ti and was s. ASHOK is with Olin Corporation, Metals Research Laboratory, 91 Shelton Avenue, New Haven, CT 06511. K. KAIN is with Mechanical and Materials Engineering Department, Box 1621, Station B, Vanderbilt University, Nashville, TN 37235. J.M. TARTAGLIA is with Climax Molybdenum Company of Michigan, 1600 Huron Parkway, P.O. Box 1568, Ann Arbor, MI 48106. N. S. STOLOFFis with Materials Engineering Department, RensselaerPolytechnic Institute, Troy, NY 12181. Manuscript submittedJune 1, 1982. METALLURGICALTRANSACTIONSA
arc-melted. The three heats of the (Fe, Ni)3V series, LRO37, also contain 0.4 pct Ti and were arc-melted. However, one heat, LRO-37-12, was melted with commercial purity ferrovanadium and, therefore, may be presumed to be less pure than the other heats. LRO-1 and LRO-23 were annealed for one hour at 1150 °C in argon and quenched in a solution of CaCI2 and dry ice. In the quenched condition the diameter was reduced to 7.6 mm by machining. The specimens were then ordered by a ten-hour anneal at 700 °C in argon and air-cooled, LRO-37 samples were sealed in silicon tubes under vacuum and annealed for 20 minutes at 1150 °C, followed by a water quench. After a reduction in diamete
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