摘要
Thermal analysis is one of the most used techniques for analyzing the behavior of aluminum alloys in order to analyze the precipitation of Guinier-Preston(GP)zones and different phases formed.In the present work,the behavior of the Al-5.46wt.%Zn-1.67wt.%Mg alloy was studied.The mechanism and kinetics of precipitation of the GP,the metastable phaseη′and the equilibrium phaseηwere investigated using DSC carried out between room temperature and 480℃at heating rates of 5,10,15 and 20℃/min.The apparent activation energies,calculated by DSC from isothermal calculation method using JMAK model,for GP,η′andηwere 56,79 and 96 kJ/mol,respectively,and those calculated by non-isothermal calculation method using Kissinger methods were 57,82 and 99 kJ/mol,respectively.The values of Avrami parameter,n,from isothermal calculation,during the precipitation of the GP,η′andηwere 1.103,1.9075 and 1.92,respectively,and those calculated by non-isothermal were 0.86,2.30 and 2.24,respectively.The results show that GP zones formation is governed by the migration of Zn and Mg atoms while the precipitation of theη′metastable phase and theηstable phase is governed by both the migration and the diffusion of the solute atoms.
热分析是研究铝合金行为最常用的技术之一,用于分析Guinier-Preston(GP)带的析出及不同相的形成。本文研究Al-5.46wt.%Zn-1.67wt.%Mg合金的行为。用DSC研究GP区、亚稳η′相和平衡η相从室温到480°C的析出机制与动力学,升温速率为5、10、15和20°C/min。根据DSC结果,用JMAK模型和等温计算法得到GP、η′和η的表面激活能分别为56、79和96 k J/mol,而用Kissinger方法和非等温计算法得到三者的表面激活能分别为57、82和99 kJ/mol。GP、η′和η析出过程中,等温计算的Avrami参数(n)值分别为1.103、1.9075和1.92,而非等温计算的n值分别为0.86、2.30和2.24。结果表明,GP区的形成由锌和镁原子的迁移控制,而η′亚稳相和η稳定相的析出由溶质原子的迁移和扩散控制。
