[meteorite-list] Etching Iron Meteorites

From: Drake <Monel_at_meteoritecentral.com>
Date: Wed, 31 Jan 2007 19:42:06 -0500
Message-ID: <01ce01c74599$cda405e0$7400a8c0_at_DADS>

While it's true that the Widmanstatten pattern was first seen in
meteorites, it is fairly commonly seen in terrestrial metal alloys.

Metals are crystals when in solid form, and undergo allotropic phase
changes when heated and cooled. Adding different metals together form
alloys and these solutions form new phases. Even these new phases
undergo phase changes when heated and cooled. So just having two metals
in solution can create several different phases. Each of these phases
have different melting points, solidification points, and temperatures
at which these phase changes take place.

All this is like water and salt... Water has a boiling point and a
freezing point. Ice, liquid water, and steam are all phases. If you add
salt, the boiling point is lowered and the freezing point is lowered.
This is just a quick example of how one thing can change the phases of
another.

In metals its exactly the same thing, except there are actually several
phases that exist when the metal alloy is in solid form.

The Widmanstatten pattern is a geometrical pattern resulting from the
formation of a new phase along certain crystallographic planes of the
parent solid solution. The orientation of the lattice in the new phase
are crystalographically related to the lattice in the parent phase.

This can happen in wrought iron alloys used for heat treating fixtures,
aluminum alloys, copper alloys and very commonly in titanium alloys. It
can also happen in HSLA alloys when improperly heat treated.

Sorry for rambling.

I am in no way a meteorite expert, but I'm very passionate about
metallurgy. I have looked at the Nantan and the Campo I have in my
metallurgical laboratory. There is no way that some of the things I've
seen could be made on earth in less than 4 billion years. If you want a
quick lesson in metallurgy, I wrote a paper explaining some of the cool
metallurgical stuff.

http://home.sprynet.com/~monel/metallurgy_faq_v11.htm

Drake


Quis Custodiet Ipsos Custodes

Drake "Doc" Damer?u
President, NEPRA
NAR Section 614
L3CC member
TRA 9934 L3
 
www.nepra.com
www.rocketmaterials.org
http://home.sprynet.com/~monel/home.htm

 
 

> -----Original Message-----
> From: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-
> bounces at meteoritecentral.com] On Behalf Of Sterling K. Webb
> Sent: Wednesday, January 31, 2007 6:43 PM
> To: Drake; meteorite-list at meteoritecentral.com
> Subject: Re: [meteorite-list] Etching Iron Meteorites
>
> Hi, Drake,
>
> > ...Widmanstatten patterns are unique to
> > meteorites. That's not true.
>
> I'll bite. In what other materials can they be found?
> Long considered definitive hereabouts. I quote one
> source: "Widmanstatten pattern or Thompson structure:
> This pattern does not appear in terrestrial iron ores.
> Its presence is diagnostic in the identification of a
> meteorite."
> Looking for a definition, I found that they form when
> "steels are cooled at a critical rate from extremely high
> temperatures. It consists of ferrite and pearlite and
> has a cross-hatched appearance due to the ferrite
> having formed along certain crystallographic planes."
> What's the likelihood of fake meteorites being made
> that way?
>
> Sterling K. Webb
> ------------------------------------------------------------
> ----- Original Message -----
> From: "Drake" <Monel at sprynet.com>
> To: <meteorite-list at meteoritecentral.com>
> Sent: Wednesday, January 31, 2007 4:52 PM
> Subject: Re: [meteorite-list] Etching Iron Meteorites
>
>
> That was I, and thank you. The Nital I was using was what I use for
> standard metallographic sample preparation at 2% to 5%. I see now I
need
> a much higher concentration.
>
> I did find one metallurgical error in that it states that
Widmanstatten
> patterns are unique to meteorites. That's not true.
>
> Drake
>
> Quis Custodiet Ipsos Custodes
>
> Drake "Doc" Damer?u
> President, NEPRA
> NAR Section 614
> L3CC member
> TRA 9934 L3
>
> www.nepra.com
> www.rocketmaterials.org
> http://home.sprynet.com/~monel/home.htm
>
>
>
>
> > -----Original Message-----
> > From: meteorite-list-bounces at meteoritecentral.com
> [mailto:meteorite-list-
> > bounces at meteoritecentral.com] On Behalf Of Gary K. Foote
> > Sent: Tuesday, January 30, 2007 6:21 PM
> > To: meteorite-list at meteoritecentral.com
> > Subject: [meteorite-list] Etching Iron Meteorites
> >
> > Hello List,
> >
> > I forget who was asking this morning, but Ruben Garcia has
graciously
> > allowed me to
> > publish his in-depth article on cutting, etching and preserving iron
> > meteorites to my
> > site.
> >
> > For those interested the URL is;
> >
> > http://www.meteorite-dealers.com/etchingandpreservation.html
> >
> > Gary
> > http://www.meteorite-dealers.com
> > ______________________________________________
> > Meteorite-list mailing list
> > Meteorite-list at meteoritecentral.com
> > http://six.pairlist.net/mailman/listinfo/meteorite-list
>
> ______________________________________________
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
>
>
> ______________________________________________
> Meteorite-list mailing list
> Meteorite-list at meteoritecentral.com
> http://six.pairlist.net/mailman/listinfo/meteorite-list
Received on Wed 31 Jan 2007 07:42:06 PM PST