Cobalt FCC/HCP phase density difference? 1

[italyct23]

Hello,

Does anyone know if there is a density difference between the FCC (alpha) phase and the HCP (eta phase)in Cobalt?

Thank you in advance,
Mike

 

[CoryPad]

According to the ASM Handbook, the densities are:

hcp: 8.832[·]10³ kg m^-3

fcc: 8.80[·]10³ kg m^-3

By the way, the hcp phase is the alpha phase, while the fcc phase is beta.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[italyct23]

Thank you so much Cory!

-Mike

 

[metengr]

CoryPad;
The ASM Metals Handbook, Desk Edition, 2nd Ed (Appendix 2, page 113) lists the allotropic transformation at 1 atm for elemental cobalt as alpha phase(FCC crystal structure) above 422 deg C , and epsilon phase (HCP crystal structure)at and below this temperature.

On page 616 of the ASM Metals Handbook, Desk Edition, 2nd Ed, the HCP crystal structure is once again reported at temperatures below 417 deg C, at and above this temperature and up until the melting point, the FCC crystal structure is reported. I would think it was beta phase as well until I looked it up out of curiosity.

 

[CoryPad]

metengr,

Looks like ASM didn't use continuity throughout its publications. I used the ASM Handbook Online, which is a duplication of the entire ASM Handbook series. My information came from Volume 2, Properties and Selection: Nonferrous Alloys and Special-Purpose Materials -> Properties of Pure Metals -> Cobalt (Co). The alpha phase is listed as close-packed hexagonal, the beta phase as face-entered cubic.

What a terrible thing for ASM to do - it is very confusing when phases and names don't agree.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[EdStainless]

In old references (Cobalt Monographs, 1960) the phases are listed as 'a' and 'e'. With alpha being FCC and stable from 417C up to the Curie temp.
The transition between the epsilon and alpha is very slugish.
The volume change on transformation has been reported as 0.24%-0.36% with the 'best' values 0.30%-0.36%.

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Corrosion never sleeps, but it can be managed.

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