Archeometallurgical Investigation of a Fragment from a Medieval Sword Blade

Abstract

AbstractA fragment from a medieval sword blade was investigated by metallography, Vickers microhardness tests and slag inclusions analysis are to extract technological information about its manufacturing process. Optical microscopy observations and microhardness measurements indicated that the sword blade was forged via hammer welding, combining different steel bars for an optimal balance of hardness and toughness. A steeling technique involved wrapping a steel bar around a composite billet, crafted by enclosing a hypoeutectoid steel bar around a near-eutectoid steel core. Moreover, it was found that the hardness of the cutting edges was increased with a quenching heat treatment. After quenching, the blade exhibited martensitic microstructure with Vickers microhardness ranging from 500 to 640 HV0.3. The compositional data of a large set of nonmetallic inclusions were collected by scanning electron microscopy coupled with X-ray dispersive spectroscopy. Slag inclusion analysis and multivariate statistics confirmed the blade's composite nature and revealed distinct smelting and forging-related SI groups. Liquidus temperatures indicated smelting temperatures of at least 1156°C for the external section and 1031°C for the internal. The forging temperature was estimated at a minimum of 1143°C. These findings provide insight into the blade’s metallurgical history.