Effect of nickel and vanadium on iron bearing intermetallic phases in AA 5657 simulated DC castings

摘要

The effect of Ni and V trace additions at various levels on the transition and distribution of Fe bearing intermetallic phases on AA 5657 was investigated with a direct chill casting simulator. Phase identification and quantification were performed using a combination of SEM, electron backscattered diffraction, energy dispersive spectrum and image analysis techniques to accurately evaluate the effect of Ni and V on ingot microstructures. The Ni addition promotes AI_3Fe and α-AIFeSi while suppressing Al_mFe. At high Ni levels, a new Ni rich AlFeNi phase was observed. On the other hand, V strongly encourages Al_mFe and lowers the critical cooling rates of the phase formation. However, at low Ni or V levels (70-150 and 170-240 ppm respectively), the effect of Ni and V on phase selection is still weak and may not significantly affect the material properties. A counteractive effect of the combined Ni and V additions on the phase selection was observed.