均匀化退火温度对7A85铝合金铸锭组织和性能的影响

Effect of homogenization annealing temperature on microstructure and properties of 7A85 aluminum alloy ingot

利用硬度计、电导率仪、光学显微镜(OM)X射线衍射物相分析(XRD)和扫描电子显微镜(SEM)研究了半连续铸造7A85铝合金铸锭经不同温度(保温24h)均匀化退火后的组织、硬度和电导率。研究结果表明:半连续激冷铸造的7A85铝合金铸锭存在严重的枝晶偏析和晶界偏析,富Zn、Mg、Cu的非平衡相以及富Fe、Mn的杂质相沿晶界呈连续的网状分布。铸锭组织中固溶体饱和程度较高,合金硬度较高,电导率较低。随着均匀化处理温度的升高,沿晶界分布的非平衡共晶相逐渐回溶至基体,基体的固溶程度逐渐升高,合金的硬度逐渐升高,电导率则逐渐降低。铸锭经470℃24h均匀化处理后,枝晶结构消失,晶界上的非平衡相基本完全回溶到基体中,铸锭缺陷消除,470℃24h为7A85铝合金铸锭最适宜的单级均匀化工艺。

The microstructure,hardness and conductivity of semi-continuous cast 7A85 aluminum alloy ingot after homogenization annealing at different temperatures(holding for 24 h)were studied by means of hardness tester and conductivity tester,optical microscope(OM),X-ray diffraction phase analysis(XRD)and scanning electron microscope(SEM).The results show that there are serious dendrite segregation and grain boundary segregation in the 7A85 aluminum alloy ingot cast by semi-continuous chilling casting,and the non-equili brium phases rich in Zn,Mg and Cuand the impurity phases rich in Fe and Mn are distributed in a continuous network along the grain boundary In the ingot structure,the solid solution saturation degree is higher,the alloy hardness is higher,and the conductivity is lower.With the increase of homogenization temperature the non-equilibrium eutectic phase distributed along the grain boundary gradually dissolves back to the matrix,the solid solution degree of the matrix gradually increases,the hardness of the alloy gradually increases,and the conductivity gradually decreases After the ingot is homogenized at 470℃for 24 hours,the dendrite structure disappears the non-equilibrium phase on the grain boundary is basically completely dissolved into the matrix,and the ingot defects are eliminated.470℃for 24 hours is the most suitable single-stage homogenization process for 7A85 aluminum alloy ingot.