Experimental Research On Casting Structure Evolve Of Cu-Fe Alloys

Because of the unique combination of strength and conductivity, in-situ deformed copper composites have potential applications as the high pulsed magnetic field conductors, lead frames and other devices. Especially, in-situ deformed Cu-Fe composites have been widely attracted since their strengths are significantly increased by the addition of Fe and the cost of Fe is lower. Optimizing the relationship between the strength and conductivity and raising the combination property are concerned in the investigations on Cu-Fe composites.In this thesis, Cu-Fe alloys with different contents of Fe are designed and prepared, and the casting process is conducted respectively by using water-cooled copper mold and graphite crucible with different cooling rate and EMS parameters. The effect of cooling rate, EMS parameters and the content of Fe on solidification structure of Cu-Fe alloys are investigated.The results show that:Fe-rich phase presents5different forms in the copper matrix. The segregation phenomena of Fe are observed in the solidification structure of Cu-Fe alloys. From top to down along axial direction of the sample, the segregation gradually reduce, grains gradually become fine, Fe-rich phase particles decreases and distributes more uniform. The diameter of spheroid cast in water cooling copper mold is mainly about10-20μm, whereas it is about30-40μm while cast in graphite crucible. With increasing the cooling rate, grains become fine; precipitation of Fe-rich phase is more uniform and finer. With increasing content of Fe, the number of dendrites reduces, the size of dendrites grows larger, and segregation is aggravated.After using the electromagnetic stirring, segregation is suppressed, the size of grains becomes fine, and a white mesh copper-rich region generates in the macrostructure. With increasing stirring intensity, the white mesh copper-rich region increases at first, and then decreases, also the white mesh structure becomes denser. With increasing the stirring current, the Fe phase gradually moves to the center, and aggregates, the average spherulite diameter decreases; with increasing the stirring frequency, the average spherulite diameter decreases, grains can be fined. When the stirring frequency is about20Hz and the current is about200A, the average spherulite diameter of Cu-6%Fe alloy is only about10μm, the size of spheroid of Fe phase is a very small and its distribution is uniform. Applying the electromagnetic stirring to the solidification process of Cu-Fe alloy preparation has better effect.