A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 2 2 2 of iron carbides and matrices that result in Damascene surface patterns. Even so, obtaining true Damascene patterning was subject to uncertainty[16]. In fact, considerable scientific effort and resulting controversy has only recently been resolved to explain the occurrence, or non-occurrence, of Damascene patterning[17]. The arrow in Fig. 6b indicates a missing piece owing to post-manufacturing brittle fracture. This breakage and a large brittle crack in an almost identical plaque[16] retroactively demonstrate some of the difficulty of smithing UHC steels. EMPIRICISM AND CORROSION PROTECTION The empirically based achievements of ironmasters and smiths in ancient and historic times are amazing, both because of the complexity of production and processing, and the fact that scientific explanations began only in the late 19th century A.D. Not so amazing, but very important, is the problem of protecting archaeological iron and steel objects from continuing damage by corrosion. This is obvious from the objects portrayed in Figs. 3a, 3b, 4a, and 6a. Excellent handbooks for conservation are available[18‒20]. ~AM&P For more information: Omid Oudbashi, associate professor, department of conservation of cultural and historical properties and archaeometry, Art University of Isfahan, P.O. Box 1744, Isfahan, Iran, o.oudbashi@aui.ac.ir, www. aui.ac.ir. Russell Wanhill, emeritus principal research scientist, aerospace vehicles division, Royal Netherlands Aerospace Centre, Amsterdam and Marknesse, theNetherlands, rjhwanhill@ gmail.com. References 1. O. Oudbashi and R.J.H. Wanhill, Archaeometallurgy of Copper and Silver Alloys in the Old World, Advanced Materials & Processes, 179(5), p 24-27, 2021. 2. N.L. Erb-Satullo, The Innovation and Adoption of Iron in the Ancient Near East, Journal of Archaeological Research, 27, p 557-607, 2019. 3. D. Dungworth, Who’s Afraid of the Bowl Furnace? Historical Metallurgy, 48(1,2), p 1-7, 2014 (published 2015). 4. E.J. Wynne and R.F. Tylecote, An Experimental Investigation into Primitive Iron-smelting Technique, Journal of the Iron and Steel Institute, 190, p 339-348, 1958. 5. B. Girbal, Experimenting with the Bowl Furnace, Accidental and Experimental Metallurgy, HMS Occasional Publications, No.7, p 83-92, 2013. Fig. 6 — Crucible steel objects with Damascene surface patterns: (a) knife blade, Central Anatolia, 13th century A.D.; (b) ornamental pierced plaque, Iran, 17th century A.D.; (c) optical metallography of the etched microstructure of the blade cutting edge; (d) SEMmetallography of an etched microstructure for a sample from the plaque. Both microstructures show bands of iron carbides and matrices that give rise to Damascene patterning. However, the matrices are different: in (c) the carbides are dispersed in martensite owing to selective quenching[15]; in (d) the carbides are dispersed in a matrix of ferrite, martensite and lamellar pearlite[16]. The arrow in (b) indicates a missing piece owing to post-manufacturing brittle fracture (see main text). Figs. 6b and d courtesy of Mohammad Mortazavi. Fig. 5 — Schematics of five Roman sword designs. The most common ones were mixtures of iron and steel, while the highest quality were steel laminates hammer-welded together and sometimes carburized. The final heat treatments varied from air-cooled to quenched. Adapted fromWilliams[14]. (a) (b) (c) (d)
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