Editing Widmanstätten pattern (section)

==Structures in non-meteoritic materials==
The term {{em|Widmanstätten structure}} is also used on non-meteoritic material to indicate a structure with a geometrical pattern resulting from the formation of a new [[phase (matter)|phase]] along certain [[crystallographic plane]]s of the parent phase, such as the basketweave structure in some [[zirconium alloy]]s. The Widmanstätten structures form due to the growth of new phases within the grain boundaries of the parent metals, generally increasing the hardness and brittleness of the metal. The structures form due to the precipitation of a single crystal phase into two separate phases. In this way, the Widmanstätten transformation differs from other transformations, such as a [[martensite]] or ferrite transformation. The structures form at very precise angles, which may vary depending on the arrangement of the crystal lattices. These are usually very small structures that must be viewed through a microscope because a very long cooling rate is generally needed to produce structures visible to the naked eye. However, they usually have a great and often an undesirable effect on the properties of the alloy.<ref name="ReferenceA">''Metallography and Microstructure in Ancient and Historic Metals'' By David A. Scott – J. Paul Getty Trust 1991 Page 20–21</ref>

Widmanstätten structures tend to form within a certain temperature range, growing larger over time. In [[carbon steel]], for example, Widmanstätten structures form during [[tempering (metallurgy)|tempering]] if the steel is held within a range around {{convert|500|F|C|}} for long periods of time. These structures form as a needle or plate-like growths of [[cementite]] within the crystal boundaries of the martensite. This increases the brittleness of the steel in a way that can only be relieved by recrystallizing. Widmanstätten structures made from [[Allotropes of iron|ferrite]] sometimes occur in carbon steel, if the carbon content is below but near the [[eutectoid]] composition (~ 0.8% carbon). This occurs as long needles of ferrite within the [[pearlite]].<ref name="ReferenceA"/>

Widmanstätten structures form in many other metals as well. They will form in brass, especially if the alloy has a very high zinc content, becoming needles of zinc in the copper matrix. The needles will usually form when the brass cools from the recrystallization temperature, and will become very coarse if the brass is annealed to {{convert|1112|F|C}} for long periods.<ref name="ReferenceA"/> [[Telluric iron]], which is an iron-nickel alloy very similar to meteorites, also displays very coarse Widmanstätten structures. Telluric iron is metallic iron, rather than an ore (in which iron is usually found), and it originated from the Earth rather than from space. Telluric iron is an extremely rare metal, found only in a few places in the world. Like meteorites, the very coarse Widmanstätten structures most likely develop through very slow cooling, except that the cooling occurred in the Earth's mantle and crust rather than in the [[vacuum (space)|vacuum]] and [[microgravity]] of [[outer space|space]].<ref>''Meteoritic Iron, Telluric Iron and Wrought Iron in Greenland'' By Vagn Fabritius Buchwald, Gert Mosdal -- Kommissionen for videnskabelige Undersogelse i Gronland 1979 Page 20 on page 20</ref> Such patterns have also been seen in [[mulberry (uranium alloy)|mulberry]], a ternary uranium alloy, after [[age hardening|aging]] at or below {{val|400|u=degC}} for periods of minutes to hours produces a [[monoclinic]] ɑ{{''}} phase.<ref name="Dean" >{{Cite web
 |title=A Study of the Time-Temperature Transformation Behavior of a Uranium=7.5 weight percent Niobium-2.5 weight percent Zirconium Alloy
 |first1=C.W.
 |last1=Dean
 |date=October 24, 1969
 |id=Oak Ridge Report Y-1694
 |publisher=Union Carbide Corporation, [[Y-12 Plant]], [[Oak Ridge National Laboratory]]
 |url=https://digital.library.unt.edu/ark:/67531/metadc1033722/m2/1/high_res_d/4749751.pdf
 |pages=53–54, 65
 |access-date=February 20, 2018
 |archive-date=July 24, 2018
 |archive-url=https://web.archive.org/web/20180724134105/https://digital.library.unt.edu/ark:/67531/metadc1033722/m2/1/high_res_d/4749751.pdf
 |url-status=live
 }}</ref>

However, the appearance, the composition, and the formation process of these terrestrial Widmanstätten structures are different from the characteristic structure of iron meteorites.<ref name=Buchwald/>

When an iron meteorite is forged into a tool or weapon, the Widmanstätten patterns remain but become stretched and distorted. The patterns usually cannot be fully eliminated by blacksmithing, even through extensive working. When a knife or tool is forged from meteoric iron and then polished, the patterns appear on the surface of the metal, albeit distorted, but they tend to retain some of the original octahedral shapes and the appearance of thin lamellae crisscrossing each other.<ref name=Buchwald>{{cite book|title=''Iron and Steel in Ancient Times''|author=Vagn Fabritius Buchwald -- Det Kongelige Danske Videnskabernes Selskab |date=2005|page =26|url=https://books.google.com/books/about/Iron_and_Steel_in_Ancient_Times.html?id=c947L8YJerUC}}</ref>