热变形参数对新型Al-Zn-Mg-Cu高强铝合金微观组织的影响

采用Gleeble-1500D热力模拟试验机进行新型Al-Zn-Mg-Cu高强铝合金的热压缩实验,变形程度为10%～80%,变形温度为300℃～450℃,应变速率为0.001s-1～10s-1。利用光学显微镜(OM)和透射显微镜(TEM)观察合金在不同压缩条件下的组织形貌特征,分析了热变形参数对微观组织的影响。研究结果表明,试验温度范围内,变形程度达到50%以上时,试样呈锻态变形组织,且变形程度的增大,有利于动态再结晶的进行;随着变形温度的升高和应变速率的减小,位错密度减小,亚晶粒尺寸增大。新型Al-Zn-Mg-Cu合金热压缩变形过程中主要的软化机制为动态回复和动态再结晶,当应变速率为0.01s-1、变形温度为300℃～400℃时,主要发生动态回复;当变形温度为450℃、应变速率在0.001s-1～10s-1范围内时,其变形以动态再结晶为主。

Influence of the deformation parameters on microstructures of a new AI-Zn-Mg-Cu high strength aluminum alloy

Hot compression test of a new Al-Zn-Mg-Cu high strength alloy was carried out on Gleeble-1500D thermal-mechanical simulator with reduction: 10%~80%,temperature: 300℃～450℃ and strain rate: 0.001s-1~10s-1.The microstructure was analyzed with optical microscope (OM) and transmitted electron microscope(TEM).Influence of hot deformation parameters such as temperature,strain rate and reduction on microstructure evolution and mechanisms was analyzed.The results indicate that at the range of test temperatures,as-cast structure changes into forged structure when the reduction exceeds 50%.Higher reduction is favorable to the dynamic recrystallization of the alloy.The dislocation density decreases and the subgrain size increases with increasing deforming temperature and decreasing strain rates.The main softening mechanism of the alloy is dynamic recovery and recrystallization.Dynamic recovery would occur at strain rate 0.01s-1 and temperature 300℃~400℃.Dynamic recrystallization would occur at strain rate 0.001s-1~10s-1 and temperature 450℃.