高麗青銅貨：海東通寶(ヘドントンボ)の金属組織と不純物の微細構造

抄録

  The microstructure of the bronze coin, Headongtongbo, circulated around 1097 and fabricated in the Korai period (10~14^th centuries) has been investigated. The coin is 23.4 mm in diameter and 1.7 mm in thickness with weight of 4.75 g. Transmission electron microscope, X-ray diffraction, scanning electron microscope, and electron dispersive X-ray analyses are used to determine the structure of the specimen. The composition of the specimen is Cu-6.1 mass%Sn-1.4 mass%Pb-0.5 mass%S. αCu, Pb and Cu₂S grains are observed using an optical microscope. The Cu₂S phase has been observed in a Korai bronze mirror, as reported in the previous paper. The αCu phase shows a recrystallized polygonal structure. In some part of the αCu grains, twins and fine twinlike lines are observed. Cu₂S particles are dispersed in αCu grains and the grain boundary. In αCu grains near the surface, grain boundaries and the twin boundary are corroded preferentially. The Cu₂S grains retain their original shape and remain in the corroded layer. αCu corrodes from Cu₂O to CuO, and then to Cu₂CO₃(OH)₂.