鑄錠組織的效果與機理
(中南大學 材料科學與工程學院, 長沙 410083)
摘 要: 采用光學顯微鏡、 掃描電鏡及能譜分析術研究了復合添加微量Cr、 Mn、 Ti、 Zr細化7A55合金鑄錠組織的效果和機理。結果表明： 復合添加0.04%Ti+0.17% Zr能在一定程度上細化7A55合金鑄錠組織，復合添加0.20%Cr+0.20% Mn+0.03% Ti能夠顯著細化鑄錠組織， 其細化機理為含有Cr、 Mn的原子團簇作為Al3Ti形核的基底促使α-Al成核； 復合添加微量0.04%Cr+0.04%Mn+0.03%Ti+0.18%Zr產(chǎn)生了極強烈的晶粒細化效果， 其細化機理為含有Cr、 Mn的原子團簇作為Al3Ti、 Al3Zr共同形核的基底使Al3(TixZr1-x)形核， Al3(TixZr1-x)使α-Al形核。 隨著Cr、 Mn含量增加，鑄錠晶粒向枝晶化、 粗大化方向發(fā)展。
關鍵字: 7A55鋁合金；微量元素； 晶粒細化； 形核
Zr as cast 7A55 alloys
（School of Materials Science and Engineering,
Central South University, Changsha 410083, China）
Abstract: 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 results 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 α-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 (TixZr1-x), then nucleates α-Al. With increasing content of Cr and Mn in the alloy, the grains become coarse and dendritic.
Key words: 7A55 aluminium alloy; trace elements; grain refinement; nucleation
