Minerals and Metals in Ancient India v1.c20.s3.t5.4

v1.c20.s3.t5.4

Similarly the cutting edge of the Tadakanhalli axe revealed a banded structure caused by three carburized and pearlitic layers (hardness HV 120-130 and carbon 0.2-0.3 per cent) and four uncarburized and ferritic layers (HV 98-109 and carbon 0.04-0.05 per cent). A close examination of the ferritic microstructure in the uncarburized layer indicated that the diffusion of carbon was only along the grain boundaries. This probably took place around 700-800°C. The deformed state of the lamellar pearlitic structure suggests that the axe was forged below the critical temperature (around 650°C) and cooled in air. In their first communication, Agrawal *et al.* (1980-81: 99) claimed the presence of bainite and martensite in the Tadakanhalli axe which was suggestive of quench-hardening. But Chattopadhyaya (1984b: 364) pointed out that “from the published photomicrograph nothing can be ascertained about the presence of martensite or bainite”. Subsequently, Agrawal *et al.* also agreed (1990: 15) that ‘there is no indication of the Tadakanhalli axe having been hardened and tempered’.