均匀化退火工艺对Al-Zn-Mg-Cu-Zr高强合金第二相的影响

Effect of the homogenization annealing process on the second phase of a high⁃strength Al⁃Zn⁃Mg⁃Cu⁃Zr alloy

研究了不同工艺均匀化退火过程中Al-Zn-Mg-Cu-Zr合金中组织、低熔点结晶相和弥散相的演变规律。结果表明:铸态Al-Zn-Mg-Cu高强铝合金中主要结晶相为AlMgZnCu四元相,均匀化退火后该相部分消除。均匀化退火过程中,随着温度的提高及时间的延长,合金中的非平衡结晶相逐渐溶解,未溶结晶相的体积分数降低。弥散相Al3Zr的尺寸及分布取决于均匀化退火过程中的升温速度,在缓慢升温条件下,弥散相Al3Zr的尺寸细小,分布比较弥散,密度高,合金的电导率最低;随着升温速度提高,Al3Zr相的析出数量减少,尺寸增加,析出相的密度降低,合金的电导率升高。二段均匀化退火后,弥散相Al3Zr的尺寸更加细小,密度更高,平均直径为15 nm,密度为1.27×10^(15)/cm^(3)。

The effect of homogenization annealing process on the microstructure,low melt⁃ing point crystalline phase and dispersoids(Al_(3)Zr)in a high⁃strength Al⁃Zn⁃Mg⁃Cu alumi⁃num alloy was investigated.The results show that the constituent in the as⁃cast high⁃strength aluminum alloy is mainly AlZnMgCu type compound which is partly eliminated after homoge⁃nization.With the increasing of temperature and time,the non⁃equilibrium crystalline phase is dissolved and the volume fraction of the undissolved crystalline phase is decreased.The size and the distribution of the dispersoid particles obtained depends on the heat⁃up rate dur⁃ing the homogenization annealing process.At low heating rate,dispersed phase Al3Zr has a small size,relatively dispersed distribution,high density,and the alloy has the lowest con⁃ductivity.With the increase of heating rate,the quantity of precipitated Al3Zr phase decrea⁃ses,the size increases,the density of precipitated phase decreases,and the electrical con⁃ductivity of the alloy increases.After the two⁃stage homogenization annealing,the dispersed phase Al3Zr is finer and the density is higher.The average diameter is 15 nm and the density is 1.27×10^(15)/cm^(3).