Single crystal solidification of undercooled single-phase alloys

The correlation between dendritic microstructure and melt undercooling is i nvestigated to present a new technique for rapid single crystal growing, or high undercooling directional solidification (I-IUDS). In a certain range of undercooling for stable dendrite growth in a negative temperature gradie nt, this new technique is employed to prepare single crystal Ni50Cu50 bars of approximately 10 mm in diameter and 65 mm in length. Optical metallograp hy and X-ray diffraction experiments indicate that the resulting single cry stals in the directionally solidified bars are composed of dendrites approx imately parallel to each other and growing mainly in the (100) directions. The formation process and growth velocity of single crystals in an undercoo led liquid are analyzed according to the obtained results and calculated by a current dendrite growth theory, respectively. A comparison of the HUDS t echnique with the as-proposed autonomous directional solidification (ADS) p rocess is made also in the present paper.