Microstructural studies of composite Mughal period cannons of Daulatabad Fort, India, by electron backscattered diffraction and scanning electron microscopy

• Published in: X-ray spectrometry Vol. 48; no. 1; pp. 29 - 37
• Main Author: Singh, Manager Rajdeo
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 01.01.2019
• Subjects: Bimetals; Copper; Copper oxides; Deformation; Electron backscatter diffraction; Electron microscopes; Fayalite; Forge welding; Guns (ordnance); Historical metallurgy; Inclusions; Iron; Microstructure; Plastic deformation; Recrystallization; Scanning electron microscopy; Spectrometry; Sulfur; Tin; Twinning; India
• ISSN: 0049-8246; 1097-4539
• DOI: 10.1002/xrs.2981

Historical data on ancient Indian cannons have systematically been researched, but there is lack of archaeometallurgical studies on bimetallic cannons. This study revolves around 16th–17th century bimetallic Indian cannons: copper barrel with inner iron sleeve at an approximate ratio of 5:1. Scanning electron microscopy and electron backscattered diffraction techniques have been employed to know the changes in the microstructures of the metals used in making cannons. Energy dispersive spectrometry confirmed that the outer copper barrel, with 4.5 wt% tin, had inclusions of cupric oxide (Cu2O) and contained lead and sulfur. The inner sleeve, on the other hand, was primarily iron but contained fayalite (FeSiO4) and inclusions with silicon and phosphorous. Both inner (bloomery iron) and outer (copper) material had strong signatures of plastic deformation, and the cannons were stipulated to be forge welded. Deformation twinning in recrystallized iron grains of inner iron sleeve and near‐perfect extensive twinning in the inner copper barrel indicate exposures of the respective materials to such active usage. It is concluded from the deformed structures and from the presence of clear joints that the bimetallic cannons were made by a process of forge welding. This study brings actual manufacturing practices of bimetallic cannons in ancient India.