2023 年 64 巻 9 号 p. 2302-2308
A technique, which can explain the behavior of fires by using microstructural and oxide examinations of melted marks on copper wire, has been required for fire investigators. However, a study on the microstructural and oxide evolution after a fire is insufficient due to various and complicated fire conditions. In this research, changes in surface morphology, oxide layer thickness, oxidation kinetics, and microstructure were investigated at various annealing temperatures and times on the melted mark on the copper wire. The results show that the copper dendrites surrounded by (Cu+Cu2O) eutectic structure under Cu2O and CuO surface is the fingerprint of melted mark on copper wire annealed between 220°C and 600°C. At an annealing temperature of 800°C to 1000°C, the characteristic microstructure of the melted mark is Cu2O precipitates without dendrites in grains under a single layer of Cu2O. Moreover, the diffusion processes contributed to Cu2O growth could be as follows: lattice diffusion at 220°C to 400°C and grain boundary diffusion at 400°C to 1000°C.
