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The vanadium-oxygen system: Phase relations in the vanadium-rich region below 1200 °C

1970; Elsevier BV; Volume: 21; Issue: 2 Linguagem: Inglês

10.1016/0022-5088(70)90110-4

1878-2728

Jack L. Henry, S.A. O'Hare, R. A. McCune, Marion P. Krug,

Shape Memory Alloy Transformations

Alloy specimens in the high-vanadium region of the vanadium-oxygen system were prepared by the reaction of high-purity vanadium foil and oxygen. The system was studied by X-ray and metallographic examination of quenched specimens, by differential thermal analysis (D.T.A.), and by high-temperature X-ray. Solubility was determined as a function of temperature at equilibrium pressure. Equilibrium pressures were not measured. The solubility of oxygen in α-vanadium — 1.1 wt.% at 250 °C, 1.3 wt.% at 400 °C, 2.8 wt.% at 1000 °C, and 3.5 wt.% at 1200 °C—was found to be higher than previously reported. Retention of the high-temperature structure of α-vanadium by quenching is dependent upon the oxygen content and the quench rate. The α-phase cannot be retained above 2.1 wt.% oxygen even when water quenched from 1000 °C. A peritectoid transformation was found at about 510 °C between 2.2 and 4.2 wt.% oxygen. The peritectoid phase, V9O (s.s.), has a composition range at 400 °C of 2.9 to 3.9 wt.% oxygen. A martensite structure results from water quenching α-vanadium alloys having oxygen contents from about 2.2 to 3 wt.%. The martensite transforms to the stable V9O upon reheating to temperatures in the range 200 °–250 °C. β-vanadium has a composition range at 1000 °C from 4.3 to slightly over 10 wt.% oxygen.