Li对Al-Zn-Mg-Cu系合金GP区转变动力学的影响

Influence of Li on kinetics of GP zones transformation in Al-Zn-Mg-Cu alloys

Al Zn Mg Cu系合金在较低温度时效时,形成2种类型的GP区:GP(Ⅰ)区和GP(Ⅱ)区。选用7075,7075+0.58%Li,7075+0.89%Li和7075+1.0%Li4种合金进行343K,240h和393K,24h时效,以获得GP区,并通过DSC实验结果,用Avrami Johnson Mehl(AJM)表达式计算了GP区溶解动力学参数,从而定量地研究Li对7075合金GP区转变的影响。结果表明:经过343K,240h时效后,含Li的7075合金的GP(Ⅰ)区溶解激活能较7075合金的略低,Li促进GP(Ⅰ)区的形成;经过393K,24h时效后,2种合金GP区溶解激活能相差不大。

Two types of GP zones, GP(Ⅰ) zone and GP(Ⅱ) zone, are formed during aging at lower temperature in AlZnMgCu alloys.The influence of Li on the GP zones transformation was studied for 7075, 7075+0.58%Li, 7075+0.89%Li and 7075+1.0%Li alloys after solution treatment followed by aging at 343 K for 240 h and at 393 K for 24 h by using DSC. The kinetic parameters for GP zones dissolution were calculated by using AvramiJohnsonMehl(AJM) equation.It is found that Li accelerates GP(Ⅰ) zone transformation and suppresses GP(Ⅱ) zone. The activation energy for GP zone dissolution in 7075Li alloy is lower slightly than that in 7075 alloy aged at 343 K, but basically equal to that in 7075 alloy aged at 393 K.