电流均匀化对7B04铝合金组织和性能的影响

Microstructure and Properties of 7B04 Aluminum Alloy during Homogenization by Direct Electric Current

采用硬度、电导率测试、X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)和能谱分析技术(EDS)分析了不同均匀化条件下7B04合金的组织演变及性能变化规律。结果表明:在均匀化过程中施加电流,随着均匀化温度的升高,合金的硬度提高,电导率下降。经420℃/2h均匀化后,残余相面积分数由铸态5.47%减少到3.87%,硬度由铸态HV80.0提高到HV135.4,电导率由铸态43.0 IACS%减少为32.5IACS%;经420℃/2 h/1000 A均匀化处理后,残余相面积分数减少到3.4%,硬度提高到HV151.2,电导率减少为30.7 IACS%;经440℃/2 h/1000 A均匀化后,合金的硬度比440℃/2 h提高9%,电导率减少8%,残余相面积分数减少22.4%。在均匀化过程中,亮白色T相(Cu28.6,Mg 18.5,Zn 32.9,Al 20.0;%,质量分数)逐渐转变为灰色S相过渡相(Cu 27.8,Mg 16.9,Zn 14.3,Al 41.0;%,质量分数),当Zn质量分数低于10%,转化为深灰色S相(Cu 40.3,Mg 14.3,Zn 9.4,Al 36.0;%,质量分数),S相在生成的同时,部分S相也在向基体中溶解。在均匀化过程中施加电流,可以促进T相向S相的转变。

The evolution of microstructures and properties of 7B04 aluminum alloy during homogenization without or with application of direct electric current were investigated by hardness test,conductivity test,X-ray diffraction（ XRD）,field emission scanning electron microscopy（ FESEM） and energy dispersive spectrometry（ EDS）. The results showed that the conductivity and the area fraction of residual phase decreased with the temperature increasing,while the hardness of homogenized alloy increased with electric current. After homogenized at 420 ℃ for 2 h,the area fraction reduced to 3. 87% from 5. 47%,the hardness increased to HV135. 4 from HV80. 0,and the conductivity reduced to 32. 5 IACS% from 43. 0 IACS%; after homogenized at 420 ℃ /2 h /1000 A,the area fraction reduced to 3. 4%,the hardness increased to HV151. 2,and the conductivity reduced to 30. 7 IACS%; the conductivity and the area fraction of residual phase decreased by 8. 0% and 22. 4%,respectively,and the hardness increased by 9. 0% after homogenized at 440 ℃ for2 h with the electric current of 1000 A. During the homogenization,the bright white T phase（ Cu 28. 6,Mg 18. 5,Zn 32. 9,Al 20. 0;%,mass fraction） transformed gradually to gray S phase（ Cu 27. 8,Mg 16. 9,Zn 14. 3,Al 41. 0; %,mass fraction）; when the content of Zn mass fraction was less than 10%,it turned into dark gray S phase（ Cu 40. 3,Mg 14. 3,Zn 9. 4,Al 36. 0; %,mass fraction）. During the generation of S phase,part of S phase dissolved into matrix simultaneously. The electric current applied during the homogenization could accelerate the transformation of T phase to S phase.