The effect of various parameters on the microstructure of CCA wires (Copper-clad aluminum wires) in a fire environment is an important data support for fire investigation and identification work. Due to the complexity of the influencing factors at the fire scene, it is difficult to find the cause of the fire at present. Therefore, this paper simulates the temperature, time, and cooling mode in the fire environment to study its effect on the microstructure and mechanical properties of CCA wires. The results show that the size of the grains on the outer surface of the CCA wires, the morphology and characteristics of the cross-section grains, and the Cu-Al IMCs at the interfaces can be used as a basis for determining the cause of the fire. The composition of the outer surface of CCA wires is CuO from 400°C to 800°C. (1) The effect of temperature on the outer surface of CCA wires is more significant than that of time and cooling method. When the annealing time is 30 min, the maximum diameter of the grains is about 0.15 mm at 400°C, rising to 0.31 mm at 600°C, and reaching 0.58 mm at 800°C. (2) A large number of equiaxed crystals with a diameter of about 10 μm are distributed in the cross-section of the CCA wire at 400°C, and etch pits appear on the surface of the grains at 600°C. Dendritic grains of dendritic crystal morphology are observed in the cross-section at 800°C. (3) IMCs layer (Intermetallic compounds layer) is formed in the Cu-Al interface, and the phase and thickness of the IMCs layer change with increasing temperature.
 

Fire, Copper-clad aluminum wire, Grain, Cu-Al interface, Intermetallic compounds