Optimization of grain-selection behavior in the spiral selector during Cusp-magnetic-field-assisted directional solidification of single-crystal superalloy

Cusp magnetic field (CMF) could overcome the damage of the longitudinal or transverse magnetic fields on the directional growth of dendrites in single crystal (SC) superalloy, which shows the promising prospects in the industrial application. The SC preparation is obtained by the spiral selector in industry. Thus, the work investigates the effect of CMF on the grain selection of SC superalloy with starter-block heights and temperature gradients in the spiral selector for the first time. The results show that the favorable effect of CMF on SC selection in the spiral selector is all related with the starter-block heights at the temperature gradients. At the high starter-block height, the CMF decreases the height of the selected SC in the spiral section and optimizes the selected orientation. The less grains in the entrance make the favorable effect of CMF on SC selection be realized in the spiral section. The CMF effect on SC selection in the spiral selector origins from the change of the flow field structure near the liquid-solid interface. It not only enhances the effect of grain competition and selection in the high starter block but also makes the liquid-solid interface less tilt for favorably competition growth of dendrites in the spiral channel. The investigation provides a new means and a theory instruction for optimizing the SC selection in the spiral selector.