Talk:Widmanstätten pattern

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• Structural Classification of Iron Meteorites

I don't want to start an edit war so if you agree with my point of view please restore any suitable reference removed [1] from this article. Thanks. -- Basilicofresco (msg) 21:51, 18 March 2009 (UTC)[reply]

The Discovery section contained a wealth of well-researched information with several grammatical errors (English may not have been the original contributor's native dialect). I rewrote it for tighter flow and a slightly more encyclopedic tone, making sure to retain all of the original citations/data and as many of the details as possible.

The original contributors did a fantastic job researching the information and I hope they don't mind my efforts in fine-tuning the presentation of their work. -K10wnsta (talk) 18:55, 10 September 2009 (UTC)[reply]

This article mentions Widmanstatten structures as being only in meteorites, however, Widmanstatten structures are very common in other materials as well. In the heat treatment of carbon steels, the formation of Widmanstatten structures is a common problem. In hypoeutectoid steels, the formation of ferrite Widmanstatten structures from the austenite grains occurs upon rapid cooling, whereas hypereutectoid steel form cementite Widmanstatten structures when tempered in the range of 500 degrees F for more than an hour. Nickel/aluminum bronze is another alloy known to form Widmanstatten structures. Also, Widmanstatten structures are a common feature in telluric iron. Because of this, upon its discovery in 1871 it was assumed to be meteoritic, but, by 1879, it was proven to be of terrestrial origin despite having rather coarse-grained Widmanstatten patterns. More information about Widmanstatten formation in carbon steels can be found in books like Steel Heat Treatment: Metallurgy and Technologies, Steel Heat Treatment Handbook, or scientific studies like http://www.springerlink.com/content/h402428189438068/ . Info on telluric iron can be found in books like Meteoritic Iron, Telluric Iron and Wrought Iron in Greenland, History of technology: the role of metals, Volume 6, or scientific studies like Electron microprobe analysis of terrestrial and meteoritic cohenite or http://www.minersoc.org/pages/Archive-MM/Volume_6/6-27-1.pdf . Many other sources exist as well.

It seems to me that the article should cover all aspects of Widmanstatten structures. Zaereth (talk) 19:06, 3 October 2012 (UTC)[reply]

Would it be appropriate to add a link to the article Dendrite_(metal) here? Specifically, to my untrained eye it looks like Widmanstatten patterns are a special case of more general metallurgical dendritic growth during cooling. Olawlor (talk) 02:18, 28 May 2019 (UTC)[reply]

Possibly, if you can find a way to work it into the text. A dendrite forms as a metal cools from a liquid state. Crystals within the liquid start to form, and then branch out in a fractal (tree-like) pattern. These dendritic crystals then interlock branches, and during very slow cooling, will merge to form larger and larger crystals. If the cooling is slow enough, you may end up with an object that is composed entirely of a single crystal, such as fighter-jet turbines, impact-wrench anvils and hammers, or meteorites.

Widmanstatten structures are a little different in that they form within the solid crystals from an alloy that is in a greatly supersaturated state. As the alloy cools, the supersaturing phase is literally squeezed out of the crystal and forced to precipitate along the weakest lines in the crystal lattice, like a nail driving through the grain, thus you end up with needle-shaped structures at these very precise angles, depending on the specific lattice.

You can recreate this effect with other substances such as water. At a fast enough cooling rate, water will crystallize as plate-shaped crystals of ice, forming snowflake-like dendrites. As freezing progresses, the water inside the bowl will expand and bulge the surface, putting the entire structure under great internal stresses. However, if you cool the water slowly enough, it will crystalize as a single crystal with greater strength than multiple crystals. As the liquid inside tries to freeze and expand it can't bulge the rest outward, so begins forcing its way out through the lattices, and from out of the surface of the ice will grow long, icicle-shaped spikes at a very specific angle from the surface. Zaereth (talk) 01:52, 6 June 2019 (UTC)[reply]

@Chiswick Chap: What's the "nice try," what's "plainly off topic," and what's the "original research"? Pattern welding and damascening, though they both result in patterned steel, are entirely different techniques. Reverting to "Pattern-welded steels such as Damascus steel" (emphasis added) thus creates an incorrect statement. The first source I added (Sword of the Nydam Type) introduced and defined the term pattern welding, while the second and third articles (Pattern-Welding and Damascening, parts 1 and 2) clarified the respective processes of pattern welding and damascening. The reverted statement is thus both incorrect and unsourced. --Usernameunique (talk) 19:56, 21 February 2017 (UTC)[reply]

Ah, I'm sorry, I had intended to remove the whole statement, so the revert didn't accomplish what I intended. The statement as I came to it was "Pattern welded or damascened steels also bear patterns,[14][15][16] but they are easily discernible from any Widmanstätten pattern." and my edit comment applied to all of it. The section heading "Structures in non-meteoritic materials" was I think intended to cover natural non-meteoric materials such as slowly-cooled brass, discussed in the section. Man-made steels and decorated materials seem to me to be fairly far off-topic but there is some justification for the mention, in which case your addition of citations and the mention of Damascus steel was an improvement. We should either use your version or remove the paragraph altogether. Chiswick Chap (talk) 20:13, 21 February 2017 (UTC)[reply]

I always wondered why that sentence was there, but didn't feel the gumption to mess with it. The whole sentence seems off topic to me, because this article is about a certain crystalline structure, whereas composite steels all share the same crystalline structures, mostly differing in macroscopic homogenization. (They vary distinctly in carbon content and possibly impurities, which react differently to heat-treatments.) Widmanstatten structure can appear in any of them under the right conditions, albeit rarely large enough to be visible with the naked eye. If you temper your sword wrong you'll quickly find out when they appear. If it does remain, perhaps some clarification should be made as to the differences, so the reader won't have to follow a link to find out what it's talking about.

Also, it's worthwhile to keep in mind that, until Benjaman Huntsman invented his particular form of crucible steel in the 1740s, all steels were composite steels to one extent or another. Pattern welding typically refers to the intentional formation of patterns (for example, the "Jacob's ladder" pattern in some old Damascus swords, which has never been replicated). This was originally to provide (at least in the eyes of the bladesmiths) better mechanical properties but later used for decorative purposes.

On a side note, because this article is really about a certain structure, not simply a pattern, maybe it would be less confusing to rename it "Widmanstatten structures." Zaereth (talk) 23:13, 21 February 2017 (UTC)[reply]

No problem @Chiswick Chap:! I see what you mean about the confusion. In regards to the point made by you and @Zaereth:—i.e., what is that sentence doing there—my reading is that it's attempting to differentiate natural patterns from man-made patterns. (But if @Septegram: or @Basilicofresco: want to chime in, they're the ones who, respectively, added the references to pattern welding and Damascus steel.) Not sure if that's worth keeping or not, or if it should be put somewhere else in the article, perhaps parenthetically.

Zaereth, re: pattern welding vs. damascening, they both create patterns, but in entirely different ways. As I (a relative layperson) understand it, in damascening patterns are a byproduct of the heating/cooling process; I'm unaware of the "Jacob's ladder" patterns, but assume from what you said that they were produced by this method. Pattern welding, by contrast, combines multiple rods of steel, some of which are twisted or otherwise distorted. There's a cool photo (plate XXII) in the Nydam sword article of a pattern welded sword made by Maryon before welding, showing the individual, twisted, steel rods. Patterns formed by this process are thus more mechanically than thermally derived, and display a more orderly appearance. Presumably both processes were discovered out of attempts at utilitarian design improvements before being repurposed for design. --Usernameunique (talk) 05:48, 22 February 2017 (UTC)[reply]

Oops, I meant Mohammad's Ladder. There is an excellent photo on page 21 of Cyril Stanley Smith's book, A History of Metallography. The patterns could not be the result of any heat-treatment; the more steel is heated the more the patterns diffuse together. That's just how diffusion works.

Damascus swords were forged from wootz steel, which is a composite steel formed by soaking wrought-iron plates in a crucible full of molten cast iron (often using sand or glass as a flux). The iron soaks up a good quantity of carbon and the cast iron loses some of its carbon, so what is left is a cake of steel ranging from about 1.5 to 2.0% carbon. The pattern in the Damascus swords comes from this difference in carbon content. The various patterns are the result of working the steel at very low temperatures, preventing too much diffusion of the carbon, and also low temps had to be used because the 2% carbon steel melts at a much lower temperature than the 1.5% carbon steel. (European smiths didn't like wootz, once it began to be imported from India, just because it was so difficult to forge.) It was also worked very little; just enough to bring the cake into the shape of a sword. Compared to Japanese swords, which are worked extensively and lose a great deal of carbon as a result, the Damascus swords remained at that 1.5--2% carbon after finishing. Because the hypereutectoid steel was very close to cast-iron in hardness, the swords typically required no quenching after forging; only some slight annealing. The patterns are the stretched-out result of the variation in carbon content, and of the arrangement of the wrought-iron in the crucible. The innovative use of fluxes produced a steel remarkably free of impurities despite the lack of extensive working. Zaereth (talk) 06:18, 22 February 2017 (UTC)[reply]

In contrast, modern attempts to reproduce Damascene patterns are usually based upon the European "piling" method, where stacks of small items like tools or nails were forged together. To produce such patterns in the modern age often involves forge welding strands of wire together, which vary in carbon content, but somewhat reproduces the worm-like or "watermark" patterns typical of damascene steel. Zaereth (talk) 10:39, 22 February 2017 (UTC)[reply]

@Usernameunique, if someone thinks the reference I added doesn't add to the article, or detracts from it, then I have no objection to people

being bold.

I don't remember adding it, but it seems that yes, it was an attempt to differentiate.

*Septegram*Talk*Contributions* 17:46, 27 February 2017 (UTC)[reply]

Thinking about it further, I can see some great relevance if we describe the patterns in forged meteoric steel as a comparison, such as knives forged from meteorites. These patterns are very different in appearance from Damascus steel, although they are formed in a similar way, as in the patterns are intrinsic to the original material, butare fused and stretched, becoming distorted as the meteorite is drawn out. The difference is they tend to retain that very geometric form. Buchwald describes this in detail in his books Iron and Steel in Ancient Times and Meteoritic Iron, Telluric Iron and Wrought Iron in Greenland. When I get a little more time I can look it up. Zaereth (talk) 01:53, 24 February 2017 (UTC)[reply]

@Usernameunique, here is a good photo of a real Damascus sword with the Mohammad'a ladder pattern. (Look close and you'll see it. That's a prized feature on Damascus swords.) Zaereth (talk) 21:22, 10 March 2017 (UTC)[reply]

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