The phase transformation of A(19)(Mn, Ni)(2) eutectic phase in an Al-4Ni-2Mn alloy during heat treatment

摘要

The phase transformation of Al-9(Mn, Ni)(2) eutectic phase has been observed in the Al-4Ni-2Mn alloy during heat treatment at 350 degrees C, 400 degrees C, 450 degrees C, 500 degrees C and 550 degrees C for different times, and investigated by scanning electron microscopy and transmission electron microscopy. It has been found, for the first time, that fibrous Al-9(Mn, Ni)(2) eutectic phase can transform into a ternary hexagonal kappa-phase (kappa-Al14.4Cr3.4Ni1.1-type, hP227, P6(3)/m) during the heat treatment, and the lattice parameters of Al-Ni-Mn kappa-phase have been determined to be a = 1.799 nm, c = 1.295 nm, by measuring the selected area electron diffraction patterns. Furthermore, the experimental results also show that Al-Ni-Mn x -phase prefers to nucleate at the interface between Al matrix and Al-9(Mn, Ni)(2) eutectic phase and grows into the parent phase, eventually, resulting in the breakup of the eutectic fiber at the nucleation sites.