摘要
采用行星式高能球磨机，通过室温下球磨纯元素混合粉末制备出原子数分数比为Co80Zr20的非晶合金粉末。应用X射线衍射（XRD）、差示扫描量热分析仪（DSC）、扫描电镜及透射电镜对不同球磨时间的混合粉末进行了研究。结果发现，球磨时间对混合粉末的结构及颗粒形貌存在显著影响。原始混合粉末由密排六方的β-Co和α—Zr组成，经过0．5h球磨，β—Co转变为同素异构的面心立方的α—Co，随着球磨时间的增加，Co、Zr颗粒都发生严重塑性变形，并且通过冷焊团聚起来，形成具有层状结构的复合颗粒。球磨导致基体元素Co品格中的晶体缺陷密度大大增加，使得合金元素Zr原子向Co品格中扩散迁移，扩散迁移到Co晶格中的Zr原子数量随球磨时间的增加而增加，导致Co元素的品格常数单调增大。当球磨时间达到8h时，形成Co80Zr20固溶体，继续球磨至10～20h，固溶体转变为非晶。球磨20h得到的非晶粉末的玻璃化转变温度为759K，它可以在840K通过单一放热过程或者继续球磨至40h而发生晶化反应，这两种不同晶化工艺所得到的晶化产物完全相同，均为面心立方的Co23Zr6。
Amorphous binary Co80 Zr20 （at%） alloy powders were synthesized by high energy ball milling the elemental powders at room temperature. The ball - milled alloy powders for different MA times were investigated by means of X - ray diffraction （XRD）, differential scanning calorimetry （DSC）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results show that the milling time has significant effect on the powder structure and particle configuration. The starting powder consists of β- Co（hexagonal close packed）and α- Zr （hexagonal close packed）. The β- Co transforms into allotropic α - Co （face centered cubic） after milling for 0.5h. As the MA time increases, the Co and Zr powder particles are dramatically plastically deformed and flattened to platelet/pancake shapes, by the micro- forging process. These flattened particles are cold- welded together and form composite particles with lamellar structure. Ball- milling leads to an increase in the lattice defect density in the CO lattice（base material） so that the atoms of the alloying element Zr tend to migrate to the open defected lattice of metallic CO. The number of atoms of the alloying elements that migrate to the hcp lattice of the base material increase with increasing MA time, which leads to a monotonic expansion of the Co lattice. A supersaturated solid solution is obtained after MA for 8h. The solid solution is gradually transformed into a glassy phase upon increasing the MA time. The glassy powders （20h of MA time） with glass transition temperature of 759K crystallize through a single exothermic process at 840K or through further MA for 40h. The crystallized product for the two different processes is the same, fcc- Co23Zr6.
出处
《粉末冶金技术》
EI
CAS
CSCD
北大核心
2006年第5期340-344,共5页
Powder Metallurgy Technology
基金
国家"863"计划资助项目(2003AA32X151)
关键词
机械合金化
Co80Zr20合金
同素异构转变
固溶体
非晶粉末
晶化产物
mechanical alloying
Co80Zr20 alloy
allotropic transformation
solid solution
amorphous alloy powders
crystallized product
