Synchrotron microradiography of temperature gradient zone melting in directional solidification

Using synchrotron tnicroradiography, temperature gradient zone melting (TGZM) was observed in Sn-13 wt pct Bi alloy in real time during directional solidification. A significant amount of remelting was measured on the cold sides of the dendrite arms, whereas added solidification on the hot sides of the dendrite arms was observed during dendrite growth. Kinetics of TGZM was measured based on the real-time observations. TGZM had a significant effect on dendrite morphology during continuous cooling and holding within the solidification range. The presence of tertiary dendrite arms enhanced the rate of TGZM. Remelting also led to the disintegration of some secondary dendrite arms.