Abstract
Methods of metallography, transmission electron microscopy, and X-ray diffraction have been used to study the specific features of the structure formation during the fcc → hcp transformation occurring under different thermokinetic conditions in a single crystal of cobalt. It is shown that only one of four possible versions of hcp-phase crystal orientations is predominantly realized upon the β → α transformation occurring in the single crystal at a low cooling rate (V cool ∼ 1–2 K/min). It has been established that several cycles of slow heating to temperatures of 600, 800 and 1000°C and subsequent cooling of the single crystal do not increase the number of α-phase orientations. The restoration of the initial fcc-phase single-crystal orientation was observed after each heating cycle of the oriented sample, while after cooling the restoration of the preferred hcp-martensite orientation was observed; in this case, the quantity of the retained β phase fixed in the structure at room temperature increases with increasing number of cycles. After rapid quenching from 530°C into salt water (V cool ∼ 600–700 K/min), α-phase crystals of all four possible orientations are formed in the structure. Upon high-temperature quenching from 1000°C, the volume of crystal is divided into packets each containing martensite plates of predominantly one orientation. The transformation-induced recrystallization of the cobalt pseudo-single crystal quenched in salt water has been observed during repeated heating to temperatures above the β → α transformation temperature.
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Original Russian Text © Yu.V. Khlebnikova, D.P. Rodionov, V.A. Sazonova, T.I. Tabatchikova, O.V. Antonova, Yu.E. Turkhan, V.A. Kazantsev, 2007, published in Fizika Metallov i Metallovedenie, 2007, Vol. 103, No. 6, pp. 642–6451.
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Khlebnikova, Y.V., Rodionov, D.P., Sazonova, V.A. et al. Study of the structure of cobalt single crystals during the β → α transformation. Phys. Metals Metallogr. 103, 609–618 (2007). https://doi.org/10.1134/S0031918X07060105
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DOI: https://doi.org/10.1134/S0031918X07060105