The Zn ・ 2mass % Al alloy installed in a tUbular rnold of different irner diameters ( the specimen diameter )was solidified frorn the substrate in the temperature gradient . With decreasing specimen diameter , the transition from the planar growth to−the columnar growth occurred in the shorter pcriod during fUmace cooling . Howeve ら whe 皿 the specimGn d 董 ameter d reased to O . 1mm , there were two transition periods : the early transit 董 on and the delayed transition 」 t was thought that the

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... aller specimen ( 髄ameter restricted the perturbation behavior of the interface重o change the stability oondition ofthc interface , and caused thc split oft 血e t sition period . Key word :Zn ・ A1, directiona1 solidification , initial transien し { nterfacial stability . perturbation