Numerical and experimental study of electron beam floating zone melting of Iridium single crystal

Both numerical and experimental approaches were conducted to investigate the electron beam floating zone melting (EBFZM) of iridium crystal. A finite element model was established and the temperature fields under different processing parameters were calculated and discussed. The heating power, the rod diameter and the movement of heating source significantly influence the temperature distribution in the iridium rod. Once the heating starts, the temperature quickly increases and gradually reaches the steady state. The melting zone enlarges with the increase of heating power, and the critical power for obtaining a complete melting zone is 5.5 kW ∼ 6.0 kW in 20 mm-diameter Iridium rod. With the upward movement of heating source, the melting zone obviously enlarges and the lower solid/liquid (S/L) interface becomes more planar. Then how to get a complete melting zone with a suitable volume and the control of a planar S/L interface were discussed. An optimized processing window was proposed and applied to the EBFZM of iridium crystal. An iridium rod 20 mm in diameter was successfully produced and the microstructural morphologies indicated that the initial polycrystalline microstructure will evolve into single crystal.