镁基非晶合金复合材料的长周期结构形成规律

Formation of long-period order structure in Mg-based amorphous matrix composite

为了提高Mg基非晶合金的塑性,在非晶基体中引入长周期(Long Period Order,LPO)结构晶态相,研究了Y/Zn含量对LPO结构形成的影响.采用铜模铸造制备了Mg77Ni12Zn9-xY2+x(x=0,2,4,6)非晶合金复合材料.采用扫描电镜(SEM)、高分辨透射电子显微镜(HRTEM)、x-射线衍射仪(XRD)、能谱分析(EDX)等实验方法,对复合材料的组织、相组成和成分进行了研究.实验结果表明:形成具有14H类型LPO结构的最小Y/Zn值为0.57;形成均匀分布LPO相的Y/Zn比值为1.2,其中Y和Zn原子固溶在LPO结构中的比例略大于1.与Cu元素相比,Ni元素的存在使LPO结构类型由6H变为14H.通过各组成相在凝固过程中形核与长大过程,阐述了临界合金成分中LPO结构的形成过程及其热动力学机制.

In order to improve the plasticity of Mg-based amorphous alloy,the crystal phase with long-period order （LPO） structure was introduced into the Mg-based amorphous matrix,and the influence of Y/Zn ratio on the formation of LPO structure was investigated. Mg77Ni12Zn9-xY2＋x（x=0,2,4,6） amorphous matrix composites were fabricated using copper mold casting method. The microstructure,phase constituent and composition of the composites were analyzed by scanning electronic microscope （SEM）,high-resolution transmission electron microscope （HRTEM）,X-ray diffraction （XRD） and energy dispersive x-ray spectroscopy （EDX）. The results show that the minimum Y/Zn ratio to form the LPO structure with 14H type characteristic is 0.57. The Y/Zn ratio to form the LPO phase distributed uniformly in the amorphous matrix is about 1.2,where the proportion of Y and Zn atoms in the LPO structure is slightly above 1. The existance of Ni element results in a change of the LPO structure from 6H to 14H type characteristic. In addition,the formation mechanism of LPO structure in amorphous alloys with critical composition was given based on both nucleation and growth processes of various phases during solidification.