Li 对 Al-Mg-Si 合金时效过程的影响

EFFECT OF Li ADDITION ON THE PRECIPITATION BEHAVIOR AND MECHANICAL PROPERTIES OF AlMgSi ALLOY

Ａｌ－０．６Ｍｇ－０．８Ｓｉ－０．２Ｃｒ合金中加入不同含量的Ｌｉ后，无针状Ｍｇ２Ｓｉ相析出，而形成近球形ＡｌＬｉＳｉ相，δ′成为主要时效析出相。Ｌｉ的加入量为１．７％时，δ′相体积分数和晶界析出相的线密度低，其时效硬化过程缓慢，峰值强度显著降低，但具有较好的延伸率；Ｌｉ的加入量为２．６时，δ′相体积分数高，其时效硬化速度与基体合金相近，但具有更高的峰值强度，大量δ′相的存在产生强烈的共面滑移倾向，合金的延伸率略有下降。

The effect of Li content on the precipitation behavior and mechanical properties of AlMgSi alloy has been investigated. In AlLiMgSi alloy, the ordered δ′ phase became the predominant precipitate and no GP zones of Mg2Si are observed at peak aging condition. The 1.6%Li containing alloy shows slow aging reactions , limited hardening response and weak coplanar slip tendency, due to the small volume fraction of δ′ phase. While the 2.6% addition produces a strong aging response, a higher σb at peak aging condition and extensive coplanar slip tendency under tensile stress, due to the formation of large amounts of homogeneously distributed δ′ phase.