新型Al-Zn-Mg-Cu-Zr合金挤压棒材的超塑性行为研究

Superplastic Behavior of a New Al -Zn-Mg-Cu-Zr Alloy Hot Extrusion

文章通过电子背散射衍射(EBSD)、宏观织构(Texture)、扫描电镜(SEM)、透射电子显微镜(TEM)等手段研究了一种热挤压Al-Zn-Mg-Cu-Zr棒材的超塑性行为和组织演变。试验结果表明,合金在470~510℃的温度范围和5×10^-4~5×10^-3 s^-1的应变速率范围内可以实现合金的超塑性(伸长率≥200%)。在490℃和5×10^-3 s^-1变形条件下,合金的动态软化机制以动态回复为主,但动态软化过程不够充分,随着变形程度的增加,HAGBs占比减小,形变织构强度增加。同时由于Al3Zr颗粒的存在,可以有效的钉扎晶界和位错,抑制热变形过程中再结晶的发生。此外,通过分析超塑性拉伸数据可知,Al-Zn-Mg-Cu-Zr合金的平均应变速率敏感性指数和平均变形激活能分别为0.2和187.7 kJ/mol。因此,主要的超塑性变形机制是晶格扩散协调的位错攀移。

The investigation studied the superplastic behavior of the Al-Zn-Mg-Cu-Zr alloy by electron back-scattered diffraction(EBSD),texture,scanning electron microscopy(SEM)and transmission electron microscopy(TEM).It showed that:superplastic(elongations of ≥200%)can be achieved at a temperature range of 470~510 ℃ and a high strain rate range of 5×10^-4~5×10^-3 s^-1.The main softening mechanism is characterized by dynamic recovery at 490℃ and 5×10^-3 s^-1.However,the dynamic softening process inadequate,leading to the decrease of HAGBs and the increase of deformation texture intensity with the increase of the deformation degree.And the existence of Al3Zr particles can pin boundaries and dislocation to inhibit recrystallization during deformation.Analyses on the superplastic data revealed that the averages train rate sensitivity parameter and the average activation energy of the Al-Zn-Mg-Cu-Zr alloy were 0.20 and 187.7 kJ/mol,respectively.All results indicated that the main superplastic deformation mechanism was dislocation climbing.