Through electron microprobe element analysis and electron backscatter diffraction analysis,a study was conducted on the micro-area element segregation and grain distribution morphology of aluminum and copper wire melting marks caused by fire and short circuits.The results showed significant iron element segregation in both fire-induced and short-circuit-induced melting marks of aluminum wires,but with different distribution patterns:iron elements formed coarse ring-like structures in fire-induced marks,while they appeared as elongated chain-like structures in short-circuit-induced marks.For copper wires,both fire-induced and short-circuit-induced melting marks exhibited oxygen element segregation,with distinct oxide morphologies:oxides in fire-induced marks were concentrated and mainly appeared as elongated rod-like or point-like structures,whereas in short-circuit-induced marks,they were dispersed and mainly spread in a network-like pattern.Additionally,there were notable differences in grain distribution and orientation between fire-induced and short-circuit-induced melting marks of both aluminum and copper wires.Fire-induced marks were dominated by coarse equiaxed grains or dendrite-like structures,while short-circuit-induced marks were mainly characterized by coarse columnar grains.It is worth noting that grain growth in short-circuit-induced marks exhibited a clear preferential orientation,whereas no such preference was observed in fire-induced marks.
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