微量Cr、Mn、Zr、Ti、B元素对铸态AlZnMgCu合金的晶粒细化效果的影响

Effect of Minor Cr, Mn, Zr, Ti and B on Grain Refinement of As-Cast Al-Zn-Mg-Cu Alloys

摘要:

采用光学显微镜、扫描电镜和能谱分析仪考察了Cr、Mn、Zr、Ti、B的联合加入对AlZnMgCu合金的晶粒细化效果。结果发现在铸态合金中同时加入Cr-Mn-Ti-B时晶粒尺寸由256 μm 降为102 μm。而当联合加入Ti-Zr-B后能产生更加强的细化效果，晶粒平均尺寸降为55 μm。这是因为Cr、Mn原子簇团有利于促进Al3Ti形核并成为其结晶基底。当联合加入Cr、Mn、Zr、Ti、B时则可产生更加明显的晶粒细化效果，平均晶粒尺寸变为22 μm。这是因为富Cr、Mn原子簇团在成为Al3Ti结晶核心后，部分Zr原子置换了其中的Ti原子形成了新的Al3(Tix, Zr1-x)结晶核心。而过渡族金属Cr、Mn还能降低液体金属和Al3Ti和Al3(Tix, Zr1-x)的表面张力，抑制结晶核心的长大。

Abstract:

The effects of joint addition of minor elements Cr, Mn, Zr, Ti and B on grain refinement of Al-Zn-Mg-Cu alloys were investigated by optical microscopy and scanning electron microscopy（SEM）as well as EDS. Results show that grains can be refined from 256 μm to 102 μm via adding (mass fraction) 0.04%Ti, 0.18%Zr and 0.008%B to the cast alloy. Joint addition of 0.20%Cr, 0.20%Mn, 0.04%Ti and 0.008%B may attain better grain refinement, and the average grain size is as fine as 55 μm. It is because atom clusters containing minor Cr and Mn help Al3Ti nucleation to become crystallization substrate. Joint adding of 0.20%Cr, 0.20%Mn, 0.03%Ti, 0.14%Zr and 0.006%B can result in a remarkable refinement with average grain size about 22 μm. This is because a part of Zr atoms enters the crystal nuclei of Al3Ti based on the atom clusters containing minor elements Cr and Mn to replace the Ti to form new crystal nuclei Al3(Tix, Zr1-x). While minor elements Cr and Mn decrease the surface tension between liquid aluminum and solid Al3Ti, Al3Zr and Al3(Tix, Zr1-x) particles, and impede the nucleation of particles to grow up.