落管中Al_4Mn合金的形核研究

NUCLEATION OF THE A14Mn ALLOY DURING CONTAI-NERLESS SOLIDIFICATION IN A DROP TUBE

用1.2米长的落管对Al_4Mn合金进行了形核与过冷的研究.在落管底部收集到的样品中得到了正交Al_6Mn,β-Mn,两个十次准晶相关相、一个二十面体五次准晶相关相和十次准晶畴.发现这些相的含量与样品的尺寸大小有关,根据传统的形核理论对相含量与样品尺寸大小之间的关系作了定性的分析和讨论.

The nucleation and undercooling of Al4Mn alloy have been investigated with 1.2 meter long drop tube. Melt droplets were solidified in vacuum and various sizes of droplets were collected at the bottom of the tube. Besides orthorhombic Al6Mn and β-Mn phases, there are two approximants of the decagonal quasicrystal, one approximant of the icosahedral quasicrystal, and decagonal domains, observed in the droplets. However, the amount of each phase is different in samples of various sizes due to the different cooling rates and undercooling. The relationship between the phase composition and the sample size was discussed on the basis of the classical nucleation and growth theories.