Journal of Scientific & Industrial Research Vol. 76, July 2017, pp. 446-449

Short Communication

Studies on an Ancient Aircraft Material – characterization of the ancient aircraft materials Panchaloha mentioned therein. The qualitative descriptions in BVS, extreme difficulty in deciphering archaic P Anand* and C B Mohan Sanskrit terminologies, non-availability / infeasibility Centre for Incubation, Innovation Research and Consultancy in processing of the constituent materials, huge time (CIIRC), Jyothy Institute of Technology, Bengaluru gap (5000 years) and inadequate knowledge of materials science in the ancient times make the Received 13 July 2016; revised 22 December 2016; accepted 14 April 2017 research on ancient Indian materials science highly challenging and complex for a modern scientist. Even 5,7 This paper reports the preparation and characterization of the scarcely reported research on ancient aircraft Panchaloha, an ancient aircraft material, described in the ancient materials has adopted modern processing technologies Sanskrit text Bharadwaja’s Vymanika Sastra (BVS). The alloy and evidences the knowledge of materials for aircraft composition was deciphered as a leaded brass. Liquid metallurgy using coal fired blower fitted furnace was employed for applications in ancient times. Also, the report by C S 7 preparation of the specimens and they were characterized for R Prabhu reveals the properties of Panchaloha (not density, tensile properties, hardness, electrical conductivity and the Panchaloha used to make idols) mentioned in microstructure. The specimens were found to be golden yellow in BVS qualitatively. So far, there is no report in the colour and the percentage of lead in the alloy varied between 6 and 7 %. Experimental density was 6 % less than the theoretical open literature, of the properties of ancient materials density (8.88 g/cc). Ultimate Tensile Strength was 168.6 MPa and studied by adopting ancient processing methods to the specimens were found to be fairly ductile with 9.5 to 11 % validate the same with that of the ancient texts. elongation. The electrical conductivity was in the range of 25 to Hence, this research was an attempt to reproduce the 33 % of pure copper even with the presence of high amount of efforts made 5000 years ago in the area of aircraft lead in the alloy. Uniformly distributed microporosity was the main feature of the microstructure. Thus most of the properties of materials and to establish the properties of Panchaloha the alloy specimens were found to be in conformance with the quantitatively. descriptions in Bharadwaja’s Vymanika Sastra. Experimental Keywords: Ancient Aircraft Material, Leaded Brass, Preparation of panchaloha Panchaloha, Characterization The composition of Panchaloha from BVS was deciphered to be an alloy of copper, lead sulphide and Introduction zinc. The raw materials copper, lead sulphide and zinc The presence of ancient engineering marvels such were taken in the ratio 12:3:8 by weight. Coal fired as the Iron Pillar of Delhi, the Copper Statue of blower fitted furnace was employed as it was the best Gautama Buddha at Sultanganj in Bihar, and swords known melting method adopted in the ancient times. made out of Wootz steel bear testimony to the Initially, pre-weighed copper was charged into the excellence in smelting technology achieved in ancient SiC crucible (≈1 kg) pre-heated to 800 °C and India. However, no evidence exists for the ancient allowed to melt. To the molten copper, zinc was aircraft materials mentioned in Bharadwaja’s added in partial amounts with continuous stirring Vymanika Sastra1. Further, present day light weight using a graphite rod and finally addition of lead alloys made from aluminium, magnesium and sulphide powder was done in small amounts at titanium which have found wide applications in different intervals with continuous stirring to obtain aerospace technology in the modern world2,4 were homogeneity. Molten charge was held for 8 to 10 unknown in the ancient times. Hence, validation of minutes at the melting temperature and then cast into the properties described qualitatively in BVS a metal mould. necessitates a scientific study on preparation and Characterization of panchaloha samples Density, Hardness and electrical conductivity of ————— *Author for Correspondence Panchaloha specimens were measured as per ASTM E-mail: [email protected] standards. Standard tensile specimens as per ASTM E8 ANAND & MOHAN: STUDIES ON AN ANCIENT AIRCRAFT MATERIAL 447

– 2011 were prepared and tested for tensile properties Mechanical properties on a UTM (Model # TUE C - 400). Tensile properties and hardness of Panchaloha Specimens for optical metallography were prepared specimens are presented in Table 2. The strengths and as per ASTM E3-05. Clearly resolved microstructures hardness values of Panchaloha specimens were found were examined under SEM (Quanta – 200, SEIFEI, to be almost same irrespective of the variation in the Netherland). Brasses containing less than 10 % zinc amount of lead added. Hence, addition of lead in the were found to be corrosion resistant8 and similar in range of 6 to 7 % had no effect on UTS as well as the colour to that of gold to the extent that it was hardness of the alloy. Highest UTS amongst the indistinguishable from gold based on its appearance9. specimens was 168.6 MPa. Thus, the specimens Visual observation of the specimens (110 x 15 x 20 exhibited reasonable strength. Panchaloha has been mm3) revealed that they wore golden yellow described in BVS as an alloy for making of the appearance, which is in conformance with the exhaust fan blades in an ancient aircraft. Thus, the description in BVS. Chemical composition of addition of lead as per BVS was to improve the Panchaloha specimens were determined by EDAX- machinability of the alloy. Ductile properties of the Genesis analysis. Chemical Composition and density Panchaloha specimens are presented in Table 3. The values are given in Table 1. Variation in density of the percentage elongation values (9.5 to 11) indicated that specimens from 8.36 to 8.42 g/cc was observed. the Panchaloha specimens were fairly ductile. Also, Theoretical density of the alloy was determined to be the percentage elongation and percentage area around 8.88 g/cc. Deviation of 6 % between the reduction were almost identical for all the specimens theoretical and experimental densities was attributed to and hence the reproducibility of the specimens using the uniformly distributed porosity as observed in the blower fitted coal fired furnace was ensured. While SEM micrographs shown in Figure 1, which is due to there exists differences between brasses with high and the liberation of sulphur gas from lead sulphide. low zinc contents, all brasses are considered Microporosity suggests that lighter material was malleable and ductile especially low zinc brasses. obtained probably using this method in the ancient Brasses with lower zinc content can be easily cold times. Increase in the percentage of lead in the worked, welded and brazed. The specimen was specimens increased their density as expected. determined to be low zinc (around 10 %) leaded brass and therefore might have been employed for the purpose of Optical metallography making fan blades in an ancient aircraft. High copper Alpha grains were observed as matrix Figure 1 and content enables the metal to form a protective oxide layer zinc was completely dissolved in copper which was (patina) on its surface that guards against further evident from the single phase microstructure. Lead, a commonly used metal in ancient alloys being insoluble in copper, remained as elemental lead. However, it was not clearly identifiable in the micrographs. EDAX analysis indicated 6 to 7 % of lead in the alloy. Hence, Panchaloha was confirmed as a leaded brass. Table 1—Chemical Composition and Density of Panchaloha specimens Specimen Chemical Composition Densityg No /cc Cu 82.31%; Zn 10.83%; Pb 6.34%; S 1 8.36 0.19%; K 0.33% Cu 82.45%; Zn 9.77%; Pb 7.22%; S 0.23%; 2 8.42 K 0.34% Cu 83.56%; Zn 9.12%; Pb 6.95%; S 0.19%; 3 8.39 K 0.18% Cu 82.4%; Zn 10.54%; Pb 7.06%; S 0.19%; 4 8.41 K 0.33% Cu 83.48%; Zn 10.05%; Pb 6.67%; S 5 8.38 0.19%; K 0.33% Fig. 1—SEM micrograph of Panchaloha Specimen at 50X 448 J SCI IND RES VOL 76 JULY 2017

Table 2—Tensile properties and Hardness of Panchaloha Specimens Specimen No. Composition Tensile Properties (in MPa) Hardness in Yield Tensile Fracture BHN Strength Strength Stress 1 Cu 82.31%; Zn 10.83%;Pb 6.34%; S 0.19%; K 0.33% 140.24 166.34 155.93 79.98 2 Cu 82.45%; Zn 9.77%;Pb 7.22%; S 0.22%; K 0.35% 139.63 167.64 155.49 79.52 3 Cu 83.56%; Zn 9.12%;Pb 6.95%; S 0.18%; K 0.19% 140.12 165.45 154.56 78.96 4 Cu 82.4%; Zn 10.54%;Pb 7.06%; S 0.18%; K 0.34% 140.55 168.63 156.79 81.41 5 Cu 83.48%; Zn 10.05%;Pb 6.67%; S 0.19%; K 0.33% 140.46 167.26 158.39 80.62

Table 3—Ductile Properties of Panchaloha Specimens Specimen No. Composition % elongation % Area Reduction 1 Cu 82.31%; Zn 10.83%; Pb 6.34%; S 0.19%; K 0.33% 9.52 5.5 2 Cu 82.45%; Zn 9.77%; Pb 7.22%; S 0.23%; K 0.34% 11.2 5.9 3 Cu 83.56%; Zn 9.12%; Pb 6.95%; S 0.19%; K 0.18% 10.2 5.8 4 Cu 82.4%; Zn 10.54%; Pb 7.06%; S 0.19%; K 0.33% 10.7 5.6 5 Cu 83.48%; Zn 10.05%; Pb 6.67%; S 0.19%; K 0.33% 9.8 5.8

Table 4— Electrical Conductivity of Panchaloha Samples Specimen No Chemical Composition Electrical Electrical Conductivity Conductivity S/m (IACS) 1 Cu 82.31%; Zn 10.83%;Pb 6.34%; S 0.19%; K 0.33% 1.87 x 107 32.29% 2 Cu 82.45%; Zn 9.77%;Pb 7.22%; S 0.22%; K 0.35% 1.51 x 107 26.3% 3 Cu 83.56%; Zn 9.12%;Pb 6.95%; S 0.18%; K 0.19% 1.52 x 107 26.6% 4 Cu 82.4%; Zn 10.54%;Pb 7.06%; S 0.18%; K 0.34% 1.54 x 107 26.5% 5 Cu 83.48%; Zn 10.05%;Pb 6.67%; S 0.19%; K 0.33% 1.77 x 107 30.39% corrosion, a valuable property in applications that expose distributed microporosity. Although, the alloy the metal to moisture and weathering as in an aircraft. specimens exhibited good mechanical properties, the strengths are not comparable with the present day Electrical conductivity aircraft materials. But, strengths were high in terms of Panchaloha is described as a cool metal in BVS and the metals and materials known at that time. hence must possess low thermal conductivity and electrical conductivity. Table 4 presents electrical References conductivity of the specimens. Electrical conductivity was 1 Bharadwaja M & Shaastra V, Translated into English and in the range of 25 to 33 % of pure copper even with the edited by GR Josyer, Coronation Press, Mysore, (1973). presence of high amount of lead in the alloy and hence 2 Frazier W E, Lee E W, Mary E Donnellan & Thompson J suited for the application mentioned in BVS. J, Advanced Light Weight Alloys for Aerospace Applications, JOM, 41(5), (1989) 22-26. 3 Lee E W, Neu C E & Kozol J, Al-Li Alloys and Ultra Conclusion High-Strength Steels for U.S. Navy Aircraft, Featured The experiments were conducted to explore and Overview, JOM, (1990) 11-14. find the procedure employed 5000 years ago to obtain 4 James W E, The Evolution of Technology for Light lighter material from the heavy materials known at Metals Over the Last 50 Years: Al, Mg and Li that time and to examine whether the same procedure (Overview), JOM, 59 (2), (2007), 0-38. 5 Sheth N, Was Maharshi Bharadwaja a Solar Scientist? in can be adopted in the present day world. Panchaloha ‘Science and the Vedas’, Ed by Ishwarbhai Patel, specimens prepared by liquid metallurgy route using Maharshi Acad of Vedic Sci, (1984) 36-39. blower fitted coal fired furnace were found to 6 Dongre N G, Malaviya S K & Rao P R, Prakasha conform to the descriptions in BVS with respect to Stambhanabhida Loha of Maharshi Bharadwaja, IJHS, 33 colour and suitability for specific application. (4) (1998). However, the experimental density of the prepared 7 Prabhu C S R, High Technology in Ancient Sanskrit Literature–A Preliminary Report on Studies and Panchaloha specimens was 6 % less than the Investigation of Some Ancient Scientific Shastras, Sams theoretical density as evidenced from the uniformly Vign Vaib, June (1999) 46-53. ANAND & MOHAN: STUDIES ON AN ANCIENT AIRCRAFT MATERIAL 449

8 Selvaraj S, Ponmariappan S, Natesan M & Palaniswamy 9 Biswas A K, The Primacy of India in Ancient N, Dezincification of Brass and its Control : An Brass and Zinc Metallurgy, IJHS, 28(4), overview, Corros Rev, 21 (1) (2003) 41-74. (1993)309-327.