微量Cr、Mn、Ti、Zr细化7A55铝合金铸锭组织的效果与机理

Refinement mechanism of trace Cr,Mn,Ti and Zr as cast 7A55 alloys

采用光学显微镜、扫描电镜及能谱分析术研究了复合添加微量Cr、Mn、Ti、Zr细化7A55合金铸锭组织的效果和机理。结果表明:复合添加0.04%Ti+0.17%Zr能在一定程度上细化7A55合金铸锭组织,复合添加0.20%Cr+0.20%Mn+0.03%Ti能够显著细化铸锭组织,其细化机理为含有Cr、Mn的原子团簇作为Al3Ti形核的基底促使-αAl成核;复合添加微量0.04%Cr+0.04%Mn+0.03%Ti+0.18%Zr产生了极强烈的晶粒细化效果,其细化机理为含有Cr、Mn的原子团簇作为Al3Ti、Al3Zr共同形核的基底使Al3(TixZr1-x)形核,Al3(TixZr1-x)使-αAl形核。随着Cr、Mn含量增加,铸锭晶粒向枝晶化、粗大化方向发展。

The grain refinement effect and mechanism by addition of trace Cr, Mn, Ti and Zr in 7A55 cast alloy were studied by optical microscopy, scanning electron microscopy and energy dispersive spectrum（EDS）. The resuits show that adding 0.04%Ti and 0.17%Zr can refine the grain to a certain degree. Joint addition of 0.20%Cr, 0.20%Mn and 0.03%Ti has strong grain refinement effect. The refinement mechanism is that atom clusters containing minor Cr and Mn act as substrate of Al3Ti particle, which nucleate a-Al. With joint addition of 0.04%Cr, 0.04%Mn, 0.03%Ti and 0.18%Zr, a remarkable grain refinement and a fine equiaxed grains are obtained. The refinement mechanism is that atom clusters containing trace Cr and Mn nucleate Al3Ti particles which nucleates Al3 （Tix Zr1-x ）, then nucleates reAl. With increasing content of Cr and Mn in the alloy, the grains become coarse and dendritic.