Oxide and Heat Treatment Microstructure Evolution of Melted Mark on Copper Wire under Various Heat Treatment Conditions

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 degrees C and 600 degrees C. At an annealing temperature of 800 degrees C to 1000 degrees 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 degrees C to 400 degrees C and grain boundary diffusion at 400 degrees C to 1000 degrees C. [doi:10.2320/matertrans.F-M2023807]