Al3Zr弥散相对铝锌镁合金板材微观组织及强度的影响

采用室温拉伸测试, 结合金相显微镜、背散射电子衍射、透射电子显微镜、扫描透射电子显微镜等表征手段, 研究了在Al-4.4Zn-1.2Mg合金板材中引入共格Al₃Zr弥散相对其微观组织及强度的影响机理。Al₃Zr弥散相抑制了再结晶, 基于含Zr合金热轧板材中再结晶驱动力和Al₃Zr弥散相钉扎晶界阻力, 通过理论计算, 预测了再结晶分数为45%, 这与实验值40%相符。Al₃Zr弥散相提高了淬火态和时效态板材的强度。Al₃Zr弥散相平均尺寸约22.3 nm, 通过奥罗万机制阻碍位错运动, 引起强度增加值为43.3 MPa, 抑制再结晶的附加强化效果为12.6 MPa。含Zr合金板材中的晶界和亚晶界数量更多, 时效时在合金中形成了更多无强化作用的η相, 减少了η'沉淀强化相的数量, 沉淀强化作用引起的强度增加量较无Zr合金的低32.4 MPa。

Effect of Al3Zr Dispersoids on Microstructure and Strength of Al-Zn-Mg Alloy Sheets

Al₃Zr dispersoids were introduced to Al-4.4Zn-1.2Mg alloy sheets, and their effects on microstructure and strength were investigated by means of tensile test at room temperature, optical microscopy, electron back scattered diffraction, transmission electron microscopy and scanning transmission electron microscopy. Al₃Zr dispersoids inhibited recrystallization. Based on the driving force of recrystallization and retarding effect of Al3Zr dispersoids on grain boundary migration in Zr-containing alloy sheet, the recrystallization fraction was calculated to be 45%, which was almost equal to 40% of the experimental result. The presence of coherent Al₃Zr dispersoids increased the strength of the as-quenched and aged sheets. Al₃Zr dispersoids with an average size of about 22.3 nm inhibited dislocations due to Orowan strengthening, leading to an increment of about 43.3 MPa in the strength, and the recrystallization inhibition brought an additional increment of about 12.6 MPa. In the Zr-containing alloy sheet, there were a larger amount of grain boundaries and sub-grain boundaries, leading to more formation of η phase with little hardening effect, which decreased the quantity of η′ hardening phase after aging. As a result, the increment in its strength brought by precipitation hardening was 32.4 MPa lower compared to the Zr-free alloy sheet.