The State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, People's Republic of China
Abstract:
The microstructure of periodic fluctuant dendritic θ in a matrix of +θ eutectic was obtained in an Al–38 wt% Cu alloy processed by ACRT-B method grown at growth velocities (V) ranging from 5 to 60 μm/s and crucible rotating in a trapezoidal way with maximum rotation rates (Ωmax) ranging from 100 to 400 rpm. Formation of this structure is explained by the influence of the periodical Ekman flow on the growth of dendritic θ during the spin-up and spin-down process. It was also observed that the +θ eutectic between the primary dendrites of θ (CuAl2) is not periodic and fluctuant during ACRT-B process. This is quite different from our previous observation of periodic eutectic in Al–Cu eutectic processed by similar ACRT-B method.