超高压作用下锌铝合金微观组织奇异变化机理的研究

项目名称： 超高压作用下锌铝合金微观组织奇异变化机理的研究

项目编号： No.50874075

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 李荣德

作者单位： 沈阳工业大学

项目金额： 38万元

中文摘要： 常规铸造条件下Zn-Al合金凝固补缩特性差，易形成缩松、缩孔等缺陷,极大地降低了合金的机械性能，限制了合金的应用。寻求一种有效工艺方法改善ZA27合金凝固特性势在必行。本项目开展了高压下Zn-Al合金高压下凝固的组织与性能的研究，得到以下主要结论： ZA27合金在压力的作用下晶体结构发生了明显的变化，3GPa压力较常压富铝晶面的晶面间距与晶格常数随压力增加均逐渐减小。 不同压力状态下ZA27合金枝晶形态发生了显著的变化。压力处于常压至5GPa范围内，枝晶形态经历了由粗大的树枝晶、细小的树枝晶、粒状、椭球状枝晶、蠕虫状、粗大树枝晶形态的转变过程。且随着压力的升高，合金元素分布逐渐均匀，至5GPa时除了有少量元素发生偏聚外，大部分元素已经固溶到基体中。 压力改变了Zn-22Al样品的组织形貌，由常压样品的树枝晶状到高压样品的网格状；随着压力的增加，组织变得细小。凝固过程原子扩散受到抑制，使之形成过饱和固溶体，导致富铝相的对应的晶面间距及晶格常数减小。随着晶粒的细化和固溶度的增加，合金的显微硬度也增加。 压力改变了Zn-5.1Al样品的组织形貌，细化了组织，并且改变了合金的共晶点。

中文关键词： Zn-Al合金；高压凝固；微观组织；力学性能

英文摘要： The castibility of Zn-Al alloys solidified under common pressures are normally very poor. It tends to form casting shrinkage，porosities, which greatly reduces the mechanical properties of alloy and restricts the applications of the alloys. An effective processing method to improve the solidification of the alloys needs to be developed. In this project, we studied the microstructural evolution and the improvements of mechanical properties of Zn-Al alloys solidified at high pressures. The crystal structure of ZA27 alloy changes obviously solidified under high mechanical pressures. Both the crystal spacing and the lattice index of Al-rich phase are decreased when the alloy solidified at 3 GPa. The microstructures of ZA27 alloy have obvious changes under high pressures. From the environmental pressure to 5GPa pressure, the microstructures of ZA27 alloy changes from thick dendrites，fine dendrites，granular，vermiform and finally to thick dendrites. With the pressure increased, the elemental distribution of the alloys tends to be more homogeneously. Up to 5GPa pressure, the distribution of elements is very homogeneous with little detectable segregation. The morphology of the Zn-22Al alloys changed from coarse dendrite to fine latticework. Further, the lattice parameter of 3GPa specimen is remarkably smaller than that of normal pressure specimen. Besides, microhardness of the alloys is improved with the pressure. The morphology of Zn-5.1Al sample is also changed and the microstructure is refined. The eutectic point is changed.

英文关键词： Zn-Al alloy; Solidification under high pressure; Microstructure; Mechanical properties