MATERIALS CHARACIERZAION ELSEVIER Materials Characterization 45(2000)289-313 Ancient and modern laminated composites from the Great Pyramid of Gizeh to Y2K* Jeffrey Wadsworth ", Donald R. Lesuer awrence Livermore National Laboratory, University of California, PO Box 808, L-001, Livermore, CA 94551, USA Received 20 March 2000; accepted 1 June 2000 Abstract Laminated metal composites(LMCs) have been cited in antiquity; for example, an iron laminate that may date as far back as 2750 BC was found in the great Pyramid in gizeh in 1837. A laminated shield containing bronze, tin, and gold layers is described in detail by Homer. Well-known examples of steel laminates, such as an Adze blade, dating to 400 BC can be found in the literature. The Japanese sword is a laminated composite at several different levels and Merovingian blades were composed of laminated steels. Other examples are also available including composites from China, Thailand, Indonesia, Germany, Britain, Belgium, France, and Persia. The concept of lamination to provide improved properties has also found expression in modern materials. Of particular interest is the development of laminates including high-carbon and low-carbon layers. These materials have unusual properties that are of engineering interest; they are similar to ancient welded Damascus steels. The manufacture of collectable knives, labeled"welded Damascus, "has also been a focus of contemporary knife akers. Additionally, in the former Soviet Union, laminated composite designs have been used in engineering applications. Each of the above areas will be briefly reviewed, and some of the metallurgical principles will be described that underlie improvement in properties by lamination. Where appropriate, links are made between these property improvements and those that may have been present in ancient artifacts. C 2001 Elsevier Science Inc. All Keywords: Laminated metal composite; Low-carbon layer; High-carbon layer, Steel 1. Introduction metal composites(LMCs). LMCs consist of alternat ing metal or metal-containing layers that are bonded In a recent review he authors with"sharp"interfaces. These materials represent colleagues presented examples of historic unique laminated or composite form that is different nated composites and described in detail from graded materials, which have diffuse interfaces studies of the mechanical behavior of la or layered materials, in general, which can consist of altermating layers of a wide range of materials. LMCs can dramatically improve many properties including w Originally presented at the IMS Symposium held in fracture toughness, fatigue behavior, impact beha Cincinnati, OH, October 21-November 3. 1999 vior, wear, corrosion, and damping capacity: or Corresponding author. TeL: +1-925-423-2184; fax: provide enhanced formability or ductility for other +1-925-4243625 wise brittle materials. In many cases, through the E-mail address: wadsworth(lInl.gov(J. Wadsworth) choice of component materials, laminate architecture 1044-5803/00/S ont matter 2001 Elsevier Science Inc. All rights reserved. PI:S1044-5803(00)00077-2
Ancient and modern laminated composites Ð from the Great Pyramid of Gizeh to Y2K$ Jeffrey Wadsworth*, Donald R. Lesuer Lawrence Livermore National Laboratory, University of California, PO Box 808, L-001, Livermore, CA 94551, USA Received 20 March 2000; accepted 1 June 2000 Abstract Laminated metal composites (LMCs) have been cited in antiquity; for example, an iron laminate that may date as far back as 2750 BC was found in the Great Pyramid in Gizeh in 1837. A laminated shield containing bronze, tin, and gold layers is described in detail by Homer. Well-known examples of steel laminates, such as an Adze blade, dating to 400 BC can be found in the literature. The Japanese sword is a laminated composite at several different levels and Merovingian blades were composed of laminated steels. Other examples are also available, including composites from China, Thailand, Indonesia, Germany, Britain, Belgium, France, and Persia. The concept of lamination to provide improved properties has also found expression in modern materials. Of particular interest is the development of laminates including high-carbon and low-carbon layers. These materials have unusual properties that are of engineering interest; they are similar to ancient welded Damascus steels. The manufacture of collectable knives, labeled ``welded Damascus,'' has also been a focus of contemporary knife makers. Additionally, in the former Soviet Union, laminated composite designs have been used in engineering applications. Each of the above areas will be briefly reviewed, and some of the metallurgical principles will be described that underlie improvement in properties by lamination. Where appropriate, links are made between these property improvements and those that may have been present in ancient artifacts. D 2001 Elsevier Science Inc. All rights reserved. Keywords: Laminated metal composite; Low-carbon layer; High-carbon layer; Steel 1. Introduction In a recent review [1], the authors and their colleagues presented examples of historical laminated composites and described in detail modern studies of the mechanical behavior of laminated metal composites (LMCs). LMCs consist of alternating metal or metal-containing layers that are bonded with ``sharp'' interfaces. These materials represent a unique laminated or composite form that is different from graded materials, which have diffuse interfaces, or layered materials, in general, which can consist of alternating layers of a wide range of materials. LMCs can dramatically improve many properties including fracture toughness, fatigue behavior, impact behavior, wear, corrosion, and damping capacity; or provide enhanced formability or ductility for otherwise brittle materials. In many cases, through the choice of component materials, laminate architecture 1044-5803/00/$ ± see front matter D 2001 Elsevier Science Inc. All rights reserved. PII: S1044-5803(00)00077-2 $ Originally presented at the IMS Symposium held in Cincinnati, OH, October 21 ± November 3, 1999. * Corresponding author. Tel.: +1-925-423-2184; fax: +1-925-424-3625. E-mail address: wadsworth3@llnl.gov (J. Wadsworth). Materials Characterization 45 (2000) 289 ± 313
J. Wadsworth, D.R. Lesuer /Materials Characterization 45(2000)289-313 (such as volume percent of the con materials g) was discovered by an excavation team near an Ind layer thickness), and processin ry, LMCs ir passage(Southern side) in the great Pyramid at can be engineered to produce with pre- Gizeh, Egypt. The location of the plate was within scribed properties. an undisturbed section high up on the pyramid In the present paper, Section 2 deals with the The plate was removed to the British Museum and history of laminated composites. In particular, exam- was not examined for its structure until El Gayer ples of their existence, composition, and structure are nd Jones used modern metallographic techniques detailed. Extra emphasis is given to the Japanese on a small (1.7 g) sample from the plate and sword both because of its complexity as a laminate published their findings in 1989[]. A comment at several levels, and its relatively well-documented by Craddock and Lang [3 was included in the history and the technical details tha same issue of the journal story. Included at the end of the section are some The significance of the plate is twofold. First, if it comments on modern knives that duplicate, in part, can be shown to be contemporaneous with the build the ancient weapons. Section 3 first describes modern ing of the pyramid, then it is one of the oldest known engineering applications of LMCs. Scientific and plates of iron metal ever discovered and dates from engineering studies on laminated composites are then the 4th Dynasty, circa 2750 BC. Second, the metallo- presented- in some cases at the very thin-layer graphic study of El Gayer and Jones revealed that the level, and in others at layer thicknesses that were close to those found in ancient laminates. processing methods, as well as strength, durability, toughness and damping properties, are discussed. The mechan- hese laminates have been inexpertly wela ates of wrought iron and isms of ving toughn ness by lamination are de- gether by hammering. The various layers differ scribed in detail om each other in their grain sizes, carbon contents Where possible, the mechanisms leading to im- the nature of their non-metallic inclusions and in proved properties of modern engineered laminated their thicknesses composites are linked back to ancient artifacts It was further deduced from elongated non-metal- lic inclusions that the welding process had been 2. History carried out at modest temperatures( 800 C)allow- ing recrystallization of the iron matrix grains. The The idea of laminating similar or dissimilar metals bsence of metallic copper globules and only small or alloys to form a composite material has been traces of elemental copper suggested that the plate known from antiquity. The motivations for laminat had not been produced as a by-product of copper ing metals are varied. For example, in carburizing the smelting operations of iron-rich copper ores. Also, earliest forms of wrought iron, only thin layers could a chemical analysis reported in 1926 revealed only be carburized and so lamination was a way to create race levels of nickel, thereby confirming the plate ulk material. ( This could be the motivation to be of terrestrial (but not natural) origin rather most ancient laminates Another reason is that the than to be meteoric [2]. (It is noted that the above ard material, steel, was rare and it was expedient to view on lamination is not universally agreed upon sandwich it between more common materials (Thi An alternate view is that the heterogeneous nature motive is found in medieval knives )From a mechan- of te is a direct result of a heterogeneou ical viewpoint, optimizing the combination of starting piece [4]). trength, toughness, and sharpness is the basis for Summarizing, El Gayer and Jones concluded that lamination.(Examples include the Japanese sword, the iron pieces comprising the laminate were the Halberd, and modern laminates. Finally, there is a strong motivation based on decorative appeal .intentionally produced during small-scale(and, Many modern knives are made in laminated form ossibly, very primitive) operations primarily de- for this reason but it could have been a motive in signed for the production of iron metal(rather than ancient knives also. ) Some selected examples of copper metal). Furthermore, the presence of abur laminated materials follow ant inclusions of unreduced (or incompletely oxides in the metal 2.1. Laminated iron plate found at the great Pyramid laminations shows that the'smelting operations had of Gizeh rried out at low temperatures (probably between 1000"C and 1100C)and that the ron had been produced by the direct reduction In 1837, an iron plate (26 cm x 86 cm x a method maximum thickness of 0.4 cm and weighing 750 produced In which no molten iron is normally
(such as volume percent of the component materials and layer thickness), and processing history, LMCs can be engineered to produce a material with prescribed properties. In the present paper, Section 2 deals with the history of laminated composites. In particular, examples of their existence, composition, and structure are detailed. Extra emphasis is given to the Japanese sword both because of its complexity as a laminate at several levels, and its relatively well-documented history and the technical details that accompany that history. Included at the end of the section are some comments on modern knives that duplicate, in part, the ancient weapons. Section 3 first describes modern engineering applications of LMCs. Scientific and engineering studies on laminated composites are then presented Ð in some cases at the very thin-layer level, and in others at layer thicknesses that were close to those found in ancient laminates. Processing methods, as well as strength, durability, toughness, and damping properties, are discussed. The mechanisms of improving toughness by lamination are described in detail. Where possible, the mechanisms leading to improved properties of modern engineered laminated composites are linked back to ancient artifacts. 2. History The idea of laminating similar or dissimilar metals or alloys to form a composite material has been known from antiquity. The motivations for laminating metals are varied. For example, in carburizing the earliest forms of wrought iron, only thin layers could be carburized and so lamination was a way to create bulk material. (This could be the motivation for the most ancient laminates.) Another reason is that the hard material, steel, was rare and it was expedient to sandwich it between more common materials. (This motive is found in medieval knives.) From a mechanical viewpoint, optimizing the combination of strength, toughness, and sharpness is the basis for lamination. (Examples include the Japanese sword, the Halberd, and modern laminates.) Finally, there is a strong motivation based on decorative appeal. (Many modern knives are made in laminated form for this reason, but it could have been a motive in ancient knives also.) Some selected examples of laminated materials follow. 2.1. Laminated iron plate found at the Great Pyramid of Gizeh In 1837, an iron plate (26 cm 86 cm a maximum thickness of 0.4 cm and weighing 750 g) was discovered by an excavation team near an air passage (Southern side) in the Great Pyramid at Gizeh, Egypt. The location of the plate was within an undisturbed section high up on the pyramid. The plate was removed to the British Museum and was not examined for its structure until El Gayer and Jones used modern metallographic techniques on a small (1.7 g) sample from the plate and published their findings in 1989 [2]. A comment by Craddock and Lang [3] was included in the same issue of the journal. The significance of the plate is twofold. First, if it can be shown to be contemporaneous with the building of the pyramid, then it is one of the oldest known plates of iron metal ever discovered and dates from the 4th Dynasty, circa 2750 BC. Second, the metallographic study of El Gayer and Jones revealed that the plate consists of: ...numerous laminates of wrought iron and that these laminates have been inexpertly welded together by hammering. The various layers differ from each other in their grain sizes, carbon contents, the nature of their non-metallic inclusions, and in their thicknesses. It was further deduced from elongated non-metallic inclusions that the welding process had been carried out at modest temperatures ( 800°C) allowing recrystallization of the iron matrix grains. The absence of metallic copper globules and only small traces of elemental copper suggested that the plate had not been produced as a by-product of copper smelting operations of iron-rich copper ores. Also, a chemical analysis reported in 1926 revealed only trace levels of nickel, thereby confirming the plate to be of terrestrial (but not natural) origin rather than to be meteoric [2]. (It is noted that the above view on lamination is not universally agreed upon. An alternate view is that the heterogeneous nature of the plate is a direct result of a heterogeneous starting piece [4]). Summarizing, El Gayer and Jones concluded that the iron pieces comprising the laminate were: ...intentionally produced during small-scale (and, possibly, very primitive) operations primarily designed for the production of iron metal (rather than copper metal). Furthermore, the presence of abundant inclusions of unreduced (or incompletely reduced) fragments of iron oxides in the metal laminations shows that the `smelting' operations had been inexpertly carried out at low temperatures (probably between 1000°C and 1100°C) and that the iron had been produced by the `direct reduction' method Ð in which no molten iron is normally produced. 290 J. Wadsworth, D.R. Lesuer / Materials Characterization 45 (2000) 289±313
J. Wadsworth, D.R. Lesuer /Materials Characterization 45(2000) 289-313 And, most importantly, they also concluded Herbert Hoover (1928-1932), was a mining and metallurgical engineer (Stanford University, 1896) Furthermore, the metallurgical evidence supports the archaeological evidence, which suggests that the who became a famous and wealthy engineer before entering the political scene. He and his that structure was being bui wife translated the famous text de re metallica by Agricola, from the Latin to the English in 1912 Although accounts by the excavation teams em- [6, p. 421]. In that book, he footnoted his phasize the fact that the plate was found within the thoughts on the history of iron in Agricolas pyramid, and is therefore contemporaneous with the section on iron making. He considered that the amid. this view has not been generally a beginning of the Iron Age was in the prehistory period, that the egyptians knew iron 5000 to 6000 Subsequent to the paper by El Gayer and Jones, years ago, and used iron tools to carve the stones the only other investigation of the plate came in of the great pyramids. Thus, if the iron plate of 1993 by Craddock and Lang [5]. They agreed with Gizeh could be accurately dated, it would be a he El Gayer and Jones study that the structure was significant point in determining the evolution of similar to banded, wrought iron consisting of areas large, man-made, iron-based artifacts of varying carbon content. However, the absence o In order to resolve the issue of the date of the slag stringers and the presence of very large num- plate, it is possible to turn toC dating. Using this bers of other inclusions, containing unusually high technique, the dating of ancient steels has in fact levels of Ca and P, led Craddock and Lang to a been done successfully. In the last decade in parti- quite different conclusion regarding the method o cular, carbon dating on relati manufacture(and therefore the origin and likely weighing as little as a fraction of a gram to several age)of the plate. They believe the structure to be grams, has been accomplished by using accelerator one derived from "cast iron smelted with charcoal and then treated by the finery process to remove the carbon and produce a solid lump or bloom of wrought iron. "They go on to cite work proposing that this technique was the usual method of making iron in the post-medieval Islamic world. The Gizeh plate remains unusual, even in this scenario, be- ause of the very high level of inclusions that it contains. Craddock and Lang do not. on the basis of their 1993 analysis, believe the plate is con- temporaneous with the pyramid, concluding that: the plate of iron from the Great Pyramid is of no great antiquity. Nonetheless, these authors confirm that if its age were to be contemporaneous with the d that it would be the earliest substantial piece of iron known, a finding accepted by the famous scientist Petrie in 1883 Given these controversial and competing views, it is worth emphasizing the importance of the late of the plate. It is generally accepted that iron and steel were not made in this quantity until about 1500 BC. Certainly, examples exist in that me frame. some of them fame example, daggers of both gold and iron were found on Tutankhamun's mummy (Fig. 1)which known to be from 1350 BC. There are occasional claims that older pieces exist; for example, it is claimed that an iron knife blade in a museum in Turkey is from 2500 BC, but there is no supportin Fig. 1. Evidence of steel from 1350 BC. Daggers of iron and Nonetheless, some significant authors have pro- gold from Tutankhamun's grave, and their sheaths. Insert: posed a much older start to the Iron Age. For Position of iron dagger on Tutankhamun's mummy(after example, a former president of the United States, Sherby [7D
And, most importantly, they also concluded: Furthermore, the metallurgical evidence supports the archaeological evidence, which suggests that the plate was incorporated within the pyramid at the time that structure was being built. Although accounts by the excavation teams emphasize the fact that the plate was found within the pyramid, and is therefore contemporaneous with the pyramid, this view has not been generally accepted by archeologists. Subsequent to the paper by El Gayer and Jones, the only other investigation of the plate came in 1993 by Craddock and Lang [5]. They agreed with the El Gayer and Jones study that the structure was similar to banded, wrought iron consisting of areas of varying carbon content. However, the absence of slag stringers and the presence of very large numbers of other inclusions, containing unusually high levels of Ca and P, led Craddock and Lang to a quite different conclusion regarding the method of manufacture (and therefore the origin and likely age) of the plate. They believe the structure to be one derived from ``cast iron smelted with charcoal, and then treated by the finery process to remove the carbon and produce a solid lump or bloom of wrought iron.'' They go on to cite work proposing that this technique was the usual method of making iron in the post-medieval Islamic world. The Gizeh plate remains unusual, even in this scenario, because of the very high level of inclusions that it contains. Craddock and Lang do not, on the basis of their 1993 analysis, believe the plate is contemporaneous with the pyramid, concluding that: ``the plate of iron from the Great Pyramid is of no great antiquity.'' Nonetheless, these authors confirm that if its age were to be contemporaneous with the pyramid that it would be ``the earliest substantial piece of iron known,'' a finding accepted by the famous scientist Petrie in 1883. Given these controversial and competing views, it is worth emphasizing the importance of the date of the plate. It is generally accepted that iron and steel were not made in this quantity until about 1500 BC. Certainly, examples exist in that time frame, some of them famous ones. For example, daggers of both gold and iron were found on Tutankhamun's mummy (Fig. 1) which is known to be from 1350 BC. There are occasional claims that older pieces exist; for example, it is claimed that an iron knife blade in a museum in Turkey is from 2500 BC, but there is no supporting evidence presented. Nonetheless, some significant authors have proposed a much older start to the Iron Age. For example, a former president of the United States, Herbert Hoover (1928 ± 1932), was a mining and metallurgical engineer (Stanford University, 1896), who became a famous and wealthy engineer before entering the political scene. He and his wife translated the famous text De Re Metallica by Agricola, from the Latin to the English in 1912 [6, p. 421]. In that book, he footnoted his thoughts on the history of iron in Agricola's section on iron making. He considered that the beginning of the Iron Age was in the prehistory period, that the Egyptians knew iron 5000 to 6000 years ago, and used iron tools to carve the stones of the great pyramids. Thus, if the iron plate of Gizeh could be accurately dated, it would be a significant point in determining the evolution of large, man-made, iron-based artifacts. In order to resolve the issue of the date of the plate, it is possible to turn to 14C dating. Using this technique, the dating of ancient steels has in fact been done successfully. In the last decade in particular, carbon dating on relatively small samples, weighing as little as a fraction of a gram to several grams, has been accomplished by using accelerator Fig. 1. Evidence of steel from 1350 BC. Daggers of iron and gold from Tutankhamun's grave, and their sheaths. Insert: Position of iron dagger on Tutankhamun's mummy (after Sherby [7]). J. Wadsworth, D.R. Lesuer / Materials Characterization 45 (2000) 289±313 291
J. Wadsworth, D.R. Lesuer / Materials Characterization 45(2000)289-313 mass spectrometry (AMS). One of the best AMs carbon contents (up to 2.5% in both combined machines is at the Lawrence Livermore Laboratory. graphitic forms). Although these contributions The possibility of establishing a capability to confuse the dating of ancient artifacts, the presend steel and iron objects is being explored by one of of meteorite iron can be identified by its high Ni the authors and a colleague [8 content(4% to 7%)whereas terrestrial iron is rare Cresswell [9 in 1992 published a good sum- and is sufficiently well documented to not be mary of the history, issues, and limitations sur- problematical. Other complications arising from the rounding carbon dating of iron and steel artifacts. use of coal can sometimes be indirectly determined In summary, Turekian first conceived the use of Wootz steel from Sri Lanka was analyzed by C dating for artifacts and van der Merwe built a Cresswell who describes it as"ideal for C-dating system at Yale to do so in the early 1960s. The the sample size required was a mere 274 mg becaus ystem required 500 mg of carbon equivalent, of the high C content of the wootz(1.79%C) however, which corresponded to up to 1 kg o Subsequent to the work of Cresswell, other studies iron thereby severely restricting the use of the have appeared. For example, Nakamura et al. [11] technique. Developments in the 1970-1990 period dated a Japanese sword (2.27 g, 0.49%C), a planing level of tens of grams. The transition from propor Qlg.(0.93 g, 3.6%C), and an iron hook(4.53 g. succeeded in reducing sample size, but only to the adze C). Table 1 summarizes the dating of steel ional counters to the AMs technique of Cresswell artifacts using AMs. [10 in 1991 allowed reductions in carbon equiva- Thus, it is concluded that it should be possible lent to 5 mg. The sample size(which of necessity to date the iron plate at Gizeh using modern AMS depends upon the C content of the steel) ranges C techniqu from about 5 g for wrought iron (0.05% C) about 100 mg for cast iron of 2%C content. ForC dating to be meaningful, the source of C 2.2. Achilles shield used in the steel making has to be charcoal or freshly cut wood. Sources such as coal and coke are ex Perhaps the earliest known reference to improved hausted of"C. The dilution or contamination by lime properties in an LMC can be found in "The iliad of nd recycling of artifacts also has to be considered Homer"[12] in 800 BC which describes achilles Only in the 19th century did coke become a universal shield as having five layers- two bronze, two tin, fuel in the industrial world. In fact, up until the and one gold. The laminate was in the sequence Industrial Revolution, most smelting was carried out bronze/tin/gold/tin/bronze. During combat, the super- ior performance of the laminate was demonstrated by using charcoal-fired furnaces and historical records the fact that Aeneas'bronze spear penetrated the first ndicate that freshly cut wood was a fuel source. s extensive was the use of charcoal that vast deforest- two layers but stuck in the gold layer. Some details of the encounter between Aeneas and achilles can b tion took place in the US in Pennsylvania in the 17th found in translations of Homer as shown below and 18th century. In England, an act was passed by imber for fueling iron smelts. It is worth noting, ger therefor, sha thou not by words tum me till we have fought however, that the romans and the chinese from the with the bronze man to man; nay, come, let us 4th century Ad did use coaL. forthwith make tria ch of the other with Cresswell points out that meteoric iron, or even bronze-tipped spears. terrestrial iron, can also be incorporated in ancient He spake, and let drive his mighty spear against steel making and these forms can have quite high the other 's dread and wondrous shield. and loud summary of ancient iron and steel artifacts dated using theC technique by accelerator mass spectrometry %o c Age, BP 0.18 4.53 1330±110 Nakamura et al. [11 2.27 80±150 Nakamura et al. [11] Frobisher bloom 1340±70 Luriston dagger 0.30-1.0 940±60 Cresswell [9, 10] MIT dagger 0.30-10 2880±60 0.274 980±40 Cresswell [9, 1t Cast iron planing adze 3.6 0.93 1770±160 Nakamura et al. [11] Smallest sample dated
mass spectrometry (AMS). One of the best AMS machines is at the Lawrence Livermore Laboratory. The possibility of establishing a capability to age steel and iron objects is being explored by one of the authors and a colleague [8]. Cresswell [9] in 1992 published a good summary of the history, issues, and limitations surrounding carbon dating of iron and steel artifacts. In summary, Turekian first conceived the use of 14C dating for artifacts and van der Merwe built a system at Yale to do so in the early 1960s. The system required 500 mg of carbon equivalent, however, which corresponded to up to 1 kg of iron thereby severely restricting the use of the technique. Developments in the 1970 ± 1990 period succeeded in reducing sample size, but only to the level of tens of grams. The transition from proportional counters to the AMS technique of Cresswell [10] in 1991 allowed reductions in carbon equivalent to 5 mg. The sample size (which of necessity depends upon the C content of the steel) ranges from about 5 g for wrought iron (0.05% C) to about 100 mg for cast iron of 2% C content. For 14C dating to be meaningful, the source of C used in the steel making has to be charcoal or freshly cut wood. Sources such as coal and coke are exhausted of 14C. The dilution or contamination by lime and recycling of artifacts also has to be considered. Only in the 19th century did coke become a universal fuel in the industrial world. In fact, up until the Industrial Revolution, most smelting was carried out using charcoal-fired furnaces and historical records indicate that freshly cut wood was a fuel source. So extensive was the use of charcoal that vast deforestation took place in the US in Pennsylvania in the 17th and 18th century. In England, an act was passed by Queen Elizabeth I in 1558 restricting the use of timber for fueling iron smelts. It is worth noting, however, that the Romans and the Chinese from the 4th century AD did use coal. Cresswell points out that meteoric iron, or even terrestrial iron, can also be incorporated in ancient steel making and these forms can have quite high carbon contents (up to 2.5% in both combined and graphitic forms). Although these contributions could confuse the dating of ancient artifacts, the presence of meteorite iron can be identified by its high Ni content (4% to 7%) whereas terrestrial iron is rare and is sufficiently well documented to not be problematical. Other complications arising from the use of coal can sometimes be indirectly determined. Wootz steel from Sri Lanka was analyzed by Cresswell who describes it as ``ideal for 14C-dating''; the sample size required was a mere 274 mg because of the high C content of the wootz (1.79% C). Subsequent to the work of Cresswell, other studies have appeared. For example, Nakamura et al. [11] dated a Japanese sword (2.27 g, 0.49% C), a planing adze (0.93 g, 3.6% C), and an iron hook (4.53 g, 0.18% C). Table 1 summarizes the dating of steel artifacts using AMS. Thus, it is concluded that it should be possible to date the iron plate at Gizeh using modern AMS 14C techniques. 2.2. Achilles shield Perhaps the earliest known reference to improved properties in an LMC can be found in ``The Iliad of Homer'' [12] in 800 BC which describes Achilles' shield as having five layers Ð two bronze, two tin, and one gold. The laminate was in the sequence bronze/tin/gold/tin/bronze. During combat, the superior performance of the laminate was demonstrated by the fact that Aeneas' bronze spear penetrated the first two layers but stuck in the gold layer. Some details of the encounter between Aeneas and Achilles can be found in translations of Homer as shown below: But from battle, seeing I am eager therefor, shalt thou not by words turn me till we have fought with the bronze man to man; nay, come, let us forthwith make trial each of the other with bronze-tipped spears. He spake, and let drive his mighty spear against the other's dread and wondrous shield, and loud Table 1 A summary of ancient iron and steel artifacts dated using the 14C technique by accelerator mass spectrometry Object % C Grams Age, BP Reference Iron hook 0.18 4.53 1330 110 Nakamura et al. [11] Japanese sword 0.49 2.27 880 150 Nakamura et al. [11] Frobisher bloom 0.30 1.34 1340 70 Cresswell [9,10] Luriston dagger 0.30 ± 1.0 0.485 2940 60 Cresswell [9,10] MIT dagger 0.30 ± 1.0 1.44 2880 60 Cresswell [9,10] Sri Lankan wootz a 1.79 0.274 980 40 Cresswell [9,10] Cast iron planing adze 3.6 0.93 1770 160 Nakamura et al. [11] a Smallest sample dated. 292 J. Wadsworth, D.R. Lesuer / Materials Characterization 45 (2000) 289±313
J. Wadsworth, D.R. Lesuer /Materials Characterization 45(2000) 289-313 Peleus held the shield from him with his stout hand. eing seized with dread for he deemed that the far- shadowing spear of great-hearted Aeneas would lightly pierce it through- fool that he was, nor knew in his mind and heart that not easy are the they give place withal. Nor did the mighty wise-hearted Aeneas then break through the shield, for the gold stayed it, the gift of Howbeit through two folds he drave there still three, for five layers had the god welded, two of bronze, and two within of tin, nd one of gold, in which the spear of ash was Achilles then turns his spear upon Aeneas shie as made in about 400 BC. found at Al Mina on the but that shield also protects Aeneas. The contest tums realizes Achilles and Aeneas will kill each other, and thank Dr. R. Maddin for permission to publish the f ors to swords and stones. Poseidon intervenes when he and the backing piece is a low-carbon steel. The aut spirits Aeneas away while shedding a"mist over the eyes of Achilles. It is of interest to note that steel was known and described in the iliad but was not ed in the description of a tough laminated material For example, as the battle subsequently continues, tectoid. cementite stringers as a result of the Hector of the Trojans goes against Achilles but fears specialized processing of the ultrahigh carbon his fury as the flashing steel. "Later, a description o content(1.3% to 1.8% C)steels. However, it is the hardening of steel by quenching is given in quite likely that in some cases, laminated compo- the 33rd book of the iliad Achilles offer sites were developed in an attempt to duplicate the iron as a valuable prize at the funeral Damascus steel pattern. This is because such Patrochus, although there is the possibility that this pattems certainly could appear to be the result Is meteoric iron of the intimate mixing of two dissimilar metals Damascus steels were famous through the centu- ries. Their use in the Crusades by Saladin, the 23. Adze blade leader of the Saracen warriors, in a meeting with Richard the lionhearted, was immortalized by Sir The solid state joining of two dissimilar ferrous Walter Scott in his book(1871)"The Talism early as the first millennium BC [13]. The welded which was subsequently made into two movies and a BBC television mini-series, thereby bringing product often consisted of a steel and an iron. a the fame of these steels into the modern times photomicrograph is shown in Fig. 2, of an adze blade (a cutting tool used in farming), made by Greek 2.4. Chinese steel of hundred refining blacksmiths around 400 BC. The figure shows a fairly sharp interface between a carburized iron cut- Rubin describes early iron making in China in ing blade adjoining a low-carbon backing plate. The a recent paper [15]. He examined over 1000 iron blade was found at Al Mina, the ruins of a Greek artifacts from 60 iron-making sites and tombs. The trading colony on the coast of Turkey near Syria. The artifacts dated from between 900 bc and 1800 motive for using a sheet of carburized iron for the AD. Of interest to the present paper is his working face of the adze but soft iron for the other discussion of steel of hundred refinings the was an economical one based on the scarcity of phrase"hundred refinings make quality steel"is a carburized iron Chinese saying dating to the 2nd century AD It is worth noting that in about this era, it is In examination of a knife of "30 refinings from believed that Alexander the great was given a gift 112 AD. Rubin notes that the knife the India steel,“ wootz,” by the Indian King Peru. The wootz, which was contained in a gold seemed to be a box. was the starting material for the famous 6 layers. The su was proposed that the Damascus steels. The patterns on Damascus steel number of refinings ed the number of laye arise from the aggregation of spheroidized, proeu- after repeated doubling. Thus 30 and 100 refining
rang the shield about the spear-point. And the son of Peleus held the shield from him with his stout hand, being seized with dread; for he deemed that the farshadowing spear of great-hearted Aeneas would lightly pierce it through Ð fool that he was, nor knew in his mind and heart that not easy are the glorious gifts of the gods for mortal men to master or that they give place withal. Nor did the mighty spear of wise-hearted Aeneas then break through the shield, for the gold stayed it, the gift of the god. Howbeit through two folds he drave it, yet were there still three, for five layers had the crook-foot god welded, two of bronze, and two within of tin, and one of gold, in which the spear of ash was stayed [12]. Achilles then turns his spear upon Aeneas' shield, but that shield also protects Aeneas. The contest turns to swords and stones. Poseidon intervenes when he realizes Achilles and Aeneas will kill each other, and spirits Aeneas away while shedding a ``mist over the eyes of Achilles.'' It is of interest to note that steel was known and described in the Iliad, but was not used in the description of a tough laminated material. For example, as the battle subsequently continues, Hector of the Trojans goes against Achilles but fears ``his fury as the flashing steel.'' Later, a description of the hardening of steel by quenching is given. Also, in the 33rd book of the Iliad, Achilles offers a lump of iron as a valuable prize at the funeral games of Patrochus, although there is the possibility that this is meteoric iron. 2.3. Adze blade The solid state joining of two dissimilar ferrous materials is well documented as being practiced as early as the first millennium BC [13]. The welded product often consisted of a steel and an iron. A photomicrograph is shown in Fig. 2, of an adze blade (a cutting tool used in farming), made by Greek blacksmiths around 400 BC. The figure shows a fairly sharp interface between a carburized iron cutting blade adjoining a low-carbon backing plate. The blade was found at Al Mina, the ruins of a Greek trading colony on the coast of Turkey near Syria. The motive for using a sheet of carburized iron for the working face of the adze, but soft iron for the other face, was an economical one based on the scarcity of carburized iron. It is worth noting that in about this era, it is believed that Alexander the Great was given a gift of the India steel, ``wootz,'' by the Indian King, Peru. The wootz, which was contained in a gold box, was the starting material for the famous Damascus steels. The patterns on Damascus steel arise from the aggregation of spheroidized, proeutectoid, cementite stringers as a result of the specialized processing of the ultrahigh carbon content (1.3% to 1.8% C) steels. However, it is quite likely that in some cases, laminated composites were developed in an attempt to duplicate the Damascus steel pattern. This is because such patterns certainly could appear to be the result of the intimate mixing of two dissimilar metals. Damascus steels were famous through the centuries. Their use in the Crusades by Saladin, the leader of the Saracen warriors, in a meeting with Richard the Lionhearted, was immortalized by Sir Walter Scott in his book (1871) ``The Talisman,'' which was subsequently made into two movies and a BBC television mini-series, thereby bringing the fame of these steels into the modern times. 2.4. Chinese steel of hundred refinings Rubin describes early iron making in China in a recent paper [15]. He examined over 1000 iron artifacts from 60 iron-making sites and tombs. The artifacts dated from between 900 BC and 1800 AD. Of interest to the present paper is his discussion of ``steel of hundred refinings.'' The phrase ``hundred refinings make quality steel'' is a Chinese saying dating to the 2nd century AD. In examination of a knife of ``30 refinings,'' from 112 AD, Rubin notes that the knife: ...seemed to be a composite of approximately 30 ± 36 layers. The suggestion was proposed that the number of refinings specified the number of layers after repeated doubling. Thus 30 and 100 refining Fig. 2. Shown in the above figure is an Adze blade, which was made in about 400 BC, found at Al Mina on the coast of Turkey. The cutting edge is medium carbon steel and the backing piece is a low-carbon steel. The authors thank Dr. R. Maddin for permission to publish the above photograph [14]. J. Wadsworth, D.R. Lesuer / Materials Characterization 45 (2000) 289±313 293