Ancient and Modern Steels and Laminated Composites Containing Steels
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Ancient and
Modern Steels and Laminated Composites Containing Steels Jeffrey Wadsworth
Abstract A class of steels (ultrahigh-carbon steels, or UHCSs) containing high levels of carbon (i.e., 1–2 wt%) were originally developed for their superplastic characteristics. In combination with excellent room-temperature properties, the steels were developed for their commercial potential starting in the mid-1970s and continuing to the present time. The compositional similarities between these modern steels and ancient Damascus steels led to a revisiting of the history and metallurgy of Damascus and related steels. Also, as part of the development of UHCSs, modern laminated composites containing them have been designed and manufactured that have unique toughness characteristics. These laminated composites also have similarities to a range of laminated materials of historical interest. Finally, some comments are made on the utility of radiocarbon dating to determine the age of ancient irons and steels. Ten sidebars supplement this article as Web Extras on the MRS Bulletin Web site at www.mrs.org/publications/bulletin/ 2002/dec/. Keywords: Damascus steels, Japanese swords, laminated composites, radiocarbon dating, ultrahigh-carbon steels (UHCSs).
Introduction Superplasticity is the ability of polycrystalline materials to undergo extreme tensile deformation. The property of superplasticity allows complicated shapes to be manufactured cheaply, and so the subject has elicited a lot of commercial interest, starting in the 1960s. By the mid-1970s, although superplasticity had been developed in a number of alloys, no one had yet been able to develop the property in plain carbon steels, and the race was under way to do so.
History of Superplasticity (www.mrs.org/members/bulletin/2002/ dec/webextra1.html)
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Research begun in the 1970s at Stanford University under the leadership of Oleg Sherby revealed that superplasticity in steels required the addition of far more carbon than was traditionally found in commercially available compositions. Whereas commercial steels contain a maximum of 1% carbon by weight, and cast irons consist of about 2 wt% C and above, superplasticity in steels was predicted to occur in the intermediate composition range, between 1% and 2% C. Because these compositions were not commercially manufactured, the Stanford studies included the manufacture of these unique steels, and they became known as ultrahigh-carbon steels (UHCSs). In addition to demonstrating that indeed superplasticity could be found in UHCSs, it was also discovered
that the compositions of those steels were very similar to Damascus steels.
History of Damascus Steels (www.mrs.org/members/bulletin/2002/ dec/webextra2.html)
As the work on UHCSs developed from 1975 to the present time, it embraced not only superplastic behavior but also roomtemperature properties, heat treatment, and alloying effects. Several attempts to commercialize the steel were made, and patents were issued covering both compositions and processing. Following a techn
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