Effect of a high magnetic field on the microstructure in directionally solidified two-phase Ni3Al alloys

Effect of a high magnetic field on the microstructure in directionally solidified Ni-rich and Al-rich Ni3Al alloys with composition of Ni-21.5Al-0.4Zr-0.1B and Ni-26.5Al-0.4Zr-0.1B (at%), named as Ni-22Al and Ni-27Al hereafter, was investigated experimentally. Results revealed that the primary dendrites, γ-Ni dendrites in Ni-22Al and β-NiAl dendrites in Ni-27Al, were both broken by the magnetic field. However, the γ′ phase transformed into equiaxed grains along with primary dendrites in Ni-22Al, while the γ′ phase in Ni-27Al kept directional growth. The above results should be attributed to the combined action of the thermoelectric magnetic force (TEMF) acting on the dendrites and the different solidification processes of γ′ phase in these two alloys. Further, this study may initiate a method to fabricate a novel two-phase composite consisting of single crystal matrix and equiaxed dendrites.