Hi Ed,
When you heat treat your blades at night or in extreme low light you have probably noticed there are shadows that flutter in the steel at critical temperature. Why? Does anyone know? I know it is the transformation range but why do we see shadows? What is physically happening that causes our eyes to see a fluttering in the color tonality. It's very strange. Can anyone explain what we are seeing? Or is it a mystery? Another thing I have noticed and would like to get some confirmations from others is that these shadows get more pronounced the more you normalize. I normalize three times and then anneal before quenching and each time the shadows are easier to see. Am I just focusing more intensly each time or do others see this too?
Tim

BTW I saw the article on the Montana Mafia in Knives Illustrated. Yall are awesome!

Tim, I think it's the peyote you neo tribal guys chew at night. ;)

I wish. :)

Tim,
I've been fascinated with the "shadows" for quite some time. As best as I can understand it, what we are seeing is visual proof of the the steel hitting "solid solution", where the ferrite and carbides are beginning to pool into austenite.

In his recent tutorial, Max Burnett mentions the shadows and describes it as the dividing line between the Alpha and Gamma iron, which would seem to support this same idea. Don Fogg also discusses "watching the shadows" in an article on his site.

<a href="http://pub42.ezboard.com/fcustomknifedirectoryforumfrm23.showMessage?topicI D=193.topic" target="_blank">Max Burnett's Heat Treating Tutorial</a>

<a href="http://www.dfoggknives.com/hardening.htm" target="_blank">Don Fogg's Article on Heat Treating</a>

Hope this helps.

Thanks!

This shadow is the molecular phase change taking place.
The allotropic transformation occures when the "9- Body centered" cubit(molicule)reaches the lower critical temperatures and become "14- face centered" cubits (austinite or non-magnetic molicules)It is considered 1/2 liquid, 1/2 solid at that point.
When you cook an egg you can see this allotropic transformation taking place as the liquid egg becomes solid (white) do to the heat applied.However, in the case of the egg, the solid can not be returned back to the liquid form as can the steel. Just a similar example.
If you watch an egg cook slowly, you will notice a shadow that moves over the transformation site as the heat is pushed towards the center of the egg (the last part to change). First the edges then the middle, like a blade.

Due to the scientific nature of this incredible phenominon we esstablish a special name to decribe this occurance,
.........SHADOW.........:)

Darn Gene!
Allotropic....9- Body centered!?!

What side of the Brazos are you from?

I tried both babelfish.com and allword.com and neither one of those sites could translate what you said!
:)

Craig

Where'd he git all them big words? I'm just sitting here trying to imagine a nasal Texas "twang" saying...

http://www.boomspeed.com/primos/geno.jpg
(Gene Osborn)

"Awright now, lookie here ya'll, the slightly hyper-eutectoid alloy, upon being heated to Ac1 makes the allotropic shift from the body centered cubic atomic lattice structure of alpha iron to the face centered cubic atomic lattice structure of gamma iron and begins to dissolve free cementite to form austenite, jist as purdy as a spotted puppy under a new red wagon, know whut I mean?" :lol:

Just kidding Gene -- we love ya. It sounds pretty funny coming from this Louisiana hayseed too.

Those were my thoughts when the NAVY sent me to school too.
Ah, guys, I thought we were gonna cook sumpin.:)

That's why I used an egg to compare it to.

Even I can cook an egg.:)

Terry, you explained it better than I did.:)

This IS Texas! We have BIG words. We CHOOSE not to use them.
(I learned all dem words at a fancy YANKEE school)
I dunt tawk lik at off'n,Ocky doke?
BE BLESSED.