稀土钇强化Al-Zn-Mg-Cu铝合金的组织特征

Microstructure of Al-Zn-Mg-Cu aluminum alloy strengthened by yttrium element

在熔炼过程中以铝钇中间合金形式加入Y元素,研究0～0.30%范围内不同Y加入量对铝合金铸态和均匀化处理后凝固组织的影响.金相显微和扫描电镜检测结果显示:当Y的加入量在0.25%时,铸态组织中晶粒细化效果明显,晶粒度由基体的60～70μm下降到40～50μm,二次枝晶间距减小,晶界处的主要平衡相是T(AlZnMgCu)相和含Y相.经过450℃,12h的均匀化处理后,晶界不再粗大、连续,析出物呈点链状或长条状.对于0.25%Y-7055合金,晶界中析出相不再明显,晶界、晶内可见2～3μm的含Y相Al3Y和Al2Y,加Y后的合金组织材料性能得到改善.

The effects of yttrium on the microstructure of as-cast and post uniform treatment of aluminum alloys are studied in detail when yttrium is added into the melt in the form of aluminum-yttrium interalloy in the range of 0 -0.30%. When the adding amount of yttrium is 0.25% , the grain size of α（Al） is refined from 60 -70 μm to 40 -50 μm. Meanwhile the secondary dendrite space is decreased. The main equilibrium phases distributed at the grain boundary are determined as T（AlZnMgCu） and Y -containing phases. After 450 ℃ , 12 hours uniform heat treatment the grain boundary is no longer continuous. The educts exhibit as dot and strip. For 0.25% Y -7055 aluminum alloy the grain boundary is not coarse and apparent as before. There are yttrium containing phases（Al3Y and Al2Y） with 2 -3 μm size at the grain boundary and intracrystalline, which are beneficial to improve the property of aluminum alloy.