A15 Compound Deformation and Secondary Slip in V 3 Si

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A15 Compound Deformation and Secondary Slip in V3Si ROGER N. WRIGHT and KATHLEEN A. BOK The plastic deformation of AI5 compounds has been the subject of a number of investigations. Cold working is possible only under high hydrostatic pressure, and Nb3Sn, V3Si, and V3Ga polycrystals have been cold worked under hydrostatic pressures in the 1790 to 6000 MPa rangeJ~'2'3JHot deformation has been more widely evaluated, starting with the work of Greiner and Buehler in 1962. [41V3Si single crystal deformation has been studied in the 1200 to 1800 °C range, 14-~°l and V3Ga polycrystal deformation has recently been evaluated in the range from 1000 to 1300 °C.IN"2] The hot deformation of Nb3Sn polycrystals has been extensively studied in the 1150 to 1650 °C range. I'2-~51 The hot deformation stress-strain rate-temperature relationships are largely those of "power law creep", with activation energies for creep roughly in the 400 to 500 kJ/mol range. [11' 13' 141 Grain size refinement increases flow stre SS In " the power law creep regime. 1~41The hot deformed A15 compounds display polygonized dislocation structures. 17'8'9'161 Studies of hot worked V3Si have noted {100} (010) slip systems, I5'6'8'91 and dislocations with cube direction Burgers vectors have been observed. I8'9'171The creep rate in V3Si is felt to depend on dislocation climb and the diffusion of V

tions of plastically deformed V3Si single crystals and polycrystals have been undertaken. Slip in V3Si single crystals and polycrystals was studied using the etch pitting technique of Levinstein et al.tSl The materials were obtained from Bell Laboratories, Murray Hill, New Jersey. The single crystals had been compression tested to a plastic strain of about 7 pct at 1300, 1395, 1500, and 1600 °C, as reported by Mahajan et a l . t61 The compression axis was [110], with crystal plasticity dictating tension in the [1]0] direction and no plastic strain in the [001] direction. Thus, examination of a (100) plane section should reveal screw or mixed dislocation etch pits corresponding to (010)[100] glide. The specimen orientations were confirmed with standard Laue back reflection technique. The nominal (100) plane section normal was within 6 to 8 deg of the [ 100] crystallographic direction. The (100) plane sections were metallographically polished, finishing with 0 . 3 / z m alumina in chromic acid. The etch pitting was accomplished with a solution of fifteen parts concentrated hydrofluoric acid and four parts 30 pct hydrogen peroxide. Dislocation etch pits were most easily developed in the specimen plastically deformed at 1300 °C, and no etch pits could be detected in the specimen plastically deformed at 1600 °C. Representative micrographs of the (100) plane sections are shown as Figures 1 and 2. Polycrystalline V3Si material was annealed for 168 hours at 1080 °C in argon. The grain size was on the order of I mm. A 2.56 mm diameter by 5.15 mm long cylinder was compressed to a plastic strain of about 5 pct at 1300 °C, with a strain rate of about 1.7 × 10-4 s -~. The flow stre