Study of the phase transformation of cobalt

Ray, A. E.; Smith, Stewart; Scofield, James D.

doi:10.1007/bf02645161

Cited by 40 publications

(17 citation statements)

References 1 publication

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“…Nevertheless, it can be clearly inferred that the thermal hysteresis (

) increases with a rising number of thermal cycles. Fairly similar shapes and the evolution of the DSC peak in cobalt associated with the hcp↔fcc transition were observed elsewhere [ 21 , 26 , 34 ].…”

Section: Resultssupporting

confidence: 72%

The Effect of Different Thermal Treatment on the Allotropic fcc↔hcp Transformation and Compression Behavior of Polycrystalline Cobalt

et al. 2020

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Pure polycrystalline cobalt is systematically thermally treated in order to assess the effect of the microstructure on the compression behavior. Isothermal annealing of the as-drawn material leads to recrystallization and grain growth dependent on the annealing temperature (600–1100 ∘C). Consequently, the yield strength decreases and the fracture strain increases as a function of rising grain size; the content of the residual fcc phase is ~6–11%. Subsequent thermal cycling around the transition temperature is applied to further modify the microstructure, especially in terms of the fcc phase content. With the increasing number of cycles, the grain size further increases and the fraction of the fcc phase significantly drops. At the same time, the values of both the yield strength and fracture strain somewhat decrease. An atypical decrease in the fracture strain as a function of grain size is explained in terms of decreasing fcc phase content; the stress-induced fcc→hcp transformation can accommodate a significant amount of plastic strain. Besides controlling basic material parameters (e.g., grain size and texture), adjusting the content of the fcc phase can thus provide an effective means of mechanical performance optimization with respect to particular applications.

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“…Nevertheless, it can be clearly inferred that the thermal hysteresis (

Section: Resultssupporting

confidence: 72%

The Effect of Different Thermal Treatment on the Allotropic fcc↔hcp Transformation and Compression Behavior of Polycrystalline Cobalt

et al. 2020

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“…In this connection one should be aware that the allotropic transition of the pure Co from hexagonal closed packed (hcp) structure to face centered cubic (fcc) structure occurs at 695 K [28] but the transition temperature depends notably on the cooling (heating) rate [29]. The enthalpy difference of this phase change is around 0.4 kJ/mol [29], thus it is in the frame of the statistical errors of the present measurements. Nevertheless, all pertinent enthalpy values (including literature data) have been converted finally to reference states fcc Co and liquid Sn (Tables 1 and 3).…”

Section: Resultsmentioning

confidence: 96%

Calorimetric and phase diagram studies of the Co–Sn system

Vassilev

Lilova

Gachon³

2007

Intermetallics

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“…As already pointed out, the reduction of the oxides was done at 673 K (i. e. below the temperature of 695 K that is accepted as the hcp-Co ? fcc-Co transition point [1,10,11]. However, clear X-ray diffraction peaks of the hcp-Co were observed with the most Co-rich specimen No.…”

Section: Resultsmentioning

confidence: 98%

Preparation and characterization of cobalt–bismuth nano- and micro-particles

Odeh

Mahmoud

Vassilev

2007

International Journal of Materials Research

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An attempt at the preparation and characterization of Co -Bi nano-and micro-particles is presented. Firstly, predetermined compositions were obtained by simultaneous precipitation from solutions containing Bi(NO 3 ) 3 · 5 H 2 O and Co(NO 3 ) 3 · x H 2 O. The precipitates were heated under oxygen flow and in air, and thereafter reduced to metals under hydrogen flow at 673 K. Correlation between the predetermined and the actual compositions of the products was found. Characterization of the precipitates was carried out employing X-ray diffraction, scanning and transmission electron microscopy. The dimensions of the particles vary from nano-to micro-scale sizes. It was found that face centered cubic cobalt (i. e. fcc-Co modification, that is metastable up to 695 K) is the predominant cobalt phase while the hexagonal close packed cobalt (hcp-Co) is only present in small amounts. Thermodynamic calculations have shown that the molar specific surface energy of the fcc-Co should be around 0.5 J m -2 less than that of the hcp-Co (3.2 J m -2 ), in order to make the small fcc-Co particles more stable than those of hcp-Co.

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Study of the phase transformation of cobalt

Cited by 40 publications

References 1 publication

The Effect of Different Thermal Treatment on the Allotropic fcc↔hcp Transformation and Compression Behavior of Polycrystalline Cobalt

The Effect of Different Thermal Treatment on the Allotropic fcc↔hcp Transformation and Compression Behavior of Polycrystalline Cobalt

Calorimetric and phase diagram studies of the Co–Sn system

Preparation and characterization of cobalt–bismuth nano- and micro-particles

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