Effects of transverse magnetic field during directional solidification of monotectic Al-6.5wt%Bi alloy

Monotectic Al-6.5wt%Bi alloy was directionally solidified in the presence o f a transverse static homogeneous magnetic field up to 2.0 kG to determine if gravity-induced convection effects could be reduced or eliminated. Growt h rate V was varied over the range 1 to 100 mum/s, while temperature gradie nt at the liquid-solid interface was 120 K/cm. The microstructures of Al-6. 5wt%Bi alloy is characterized by regular, aligned Bi fibres or Bi droplets under given growth conditions. Morphological, thermal and magnetic analyses were carried out on sample grown with and without an applied magnetic fiel d. Results indicated that spacing and diameter of Bi fibres decreased in a transverse magnetic field, and the microstructure became more homogeneous, which means that transverse static homogeneous magnetic field can effective ly reduce or eliminate gravity-driven and thermal convection during directi onal solidification of Al-Bi monotectic alloy. (C) 2001 Kluwer Academic Pub lishers.