부산대학교 도서관

The effect of withdrawal rate on hot tearing or solidification cracking during directional solidification (DS) was explored. High withdrawal rates were found to reduce the hot tearing tendency. There is a general refinement of the microstructure when the withdrawal rate is increased. First, the dendrite arm spacing appears smaller. Second, the columnar grain size is reduced. Third, the remaining liquid is finely dispersed and increasingly discontinuous. Finally, a more uniform distribution of strain is obtained because of the presence of more grain boundaries, and grain boundary cohesion becomes stronger due to the elimination of continuous liquid films. The reduced hot tearing susceptibility is attributed to the uniform distribution of strain and stronger grain boundary cohesion.