借助光学显微镜(OM),X射线衍射仪(XRD),场发射扫描电镜(SEM-EDS)和透射电镜(TEM)研究Cr对Al-Cu-Mg-Ag合金铸态组织和双级均匀化后弥散相分布、尺寸和数量密度的影响,并采用高通量等温压缩实验研究不同等效应变下Cr对Al-Cu-Mg-Ag合金动态再结晶行为的影响.结果表明:均匀化阶段除析出棒状T-Al20Cu2Mn3弥散相外,还出现平均直径和数量密度分别为67.4 nm和4.7μm-2的球状Al7(Cr,Mn)弥散相,Cr与Mn相反的平衡分配系数(KMn<1 vs KCr>1)将无弥散相析出面积分数从29.5％ 降至13.8％,棒状的T-Al20Cu2Mn3弥散相平均长度从275.4 nm减小至147.3 nm,数量密度从3.5μm-2增至10.4μm-2.EBSD和拉伸实验结果表明,Al7(Cr,Mn)弥散相对位错运动阻碍作用减少热压缩过程中小角度晶界向大角度晶界的转变,抑制动态再结晶.Cr的添加提高Al-Cu-Mg-Ag合金不同温度下的力学性能,在25,250,300℃下Al7(Cr,Mn)弥散相对合金屈服强度的贡献值分别为21.9,16.2 MPa和15.3 MPa.
Effect of Cr on dynamic recrystallization behavior and mechanical properties of Al-Cu-Mg-Ag alloys
The effects of Cr on the microstructure of as-cast Al-Cu-Mg-Ag alloys and the distribution,size and number density of dispersoids after double-stage homogenization were investigated by OM,XRD,SEM-EDS and TEM methods. The effects of Cr on the dynamic recrystallization behavior of Al-Cu-Mg-Ag alloys under different equivalent strain were studied by high-throughput isothermal compression experiments. The results show that spherical Al7(Cr,Mn) dispersoids with average diameter and number density of 67.4 nm and 4.7 μm-2 are precipitated during the homogenization process,in addition to the rod-like T-Al20Cu2Mn3 dispersoids. The opposite equilibrium distribution coefficient of Cr and Mn (KMn<1 vs KCr>1) reduces the area fraction of dispersoid-free zones from 29.5％ to 13.8％,the average length of rod-like T-Al20Cu2Mn3 decreases from 275.4 nm to 147.3 nm,and its number density increases from 3.5 μm-2 to 10.4 μm-2. EBSD and tensile test results indicate that the Al7(Cr,Mn) dispersoids hinder the dislocation movement,reducing the transition from low-angle grain boundaries to high-angle grain boundaries during thermal compression,and inhibiting the dynamic recrystallization. The addition of Cr increases the mechanical properties of Al-Cu-Mg-Ag alloys at different temperatures,and the yield strength contributions of Al7(Cr,Mn) dispersoids to the alloys at 25,250 ℃ and 300 ℃ are 21.9,16.2 MPa and 15.3 MPa,respectively.
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