Characterizations on the instantaneously formed Ni-containing intermetallics in magnesium alloys

Instantaneous reactions of Al, Mn, Zn, Zr and Y with Ni by mixing the prepared Mg−8Al−0.4Mn, Mg−6Zn−2Y−0.5Zr and Mg−0.6Ni melts were investigated in this work to reveal the underlying mechanisms of their effects on the removal of Ni impurity. The results indicate three Ni-containing intermetallics, namely Al4NiY, Al4Ni(Y,Zr) and Al31Ni2Mn6. The former two phases present lath-like and have a relatively larger size (> 20 μm in length) than the latest one which is granular with the diameter of ∼120 nm. This illustrates that Al and Y(/Zr) can efficiently remove Ni by forming Al4NiY or Al4Ni(Y,Zr) which would precipitate to the bottom of the melt. Furthermore, adding Y into Mg−Al based alloys can simultaneously remove Fe and Ni, which contributes their excellent corrosion resistance. Finally, this paper proposes two methods helped to efficiently remove Ni for both Mg−Al based alloys and Al-free Mg alloys, and both of them are also benefit to improve alloys’ strength.