EBSD分析2024铝合金挤压型材异常椭圆环黑色条纹

EBSD study on abnormally elliptical black stripes of 2024 aluminum alloy extrusion profile

采用80 MN反向挤压2024铝合金T型材,在型材尾端出现椭圆环黑色条纹。利用金相、EBSD手段分析条纹缺陷的组织显示.椭圆环黑色条纹边部区域为再结晶组织、过渡区域为破碎组织、内部为变形组织。从边部到心部三个区域两边晶向差大于15。的晶界含量分别为45%J 9%和48%,过渡区的大角度晶界含量明显要低于另外两个区域的。黑色条纹是因大角度晶界破碎而形成的,主要是由于挤圧温度及挤压速度控制不协调导致型材截面不同区域变形不协调。通过调整挤压模具和挤压温度,避免挤压过程中不同区域变形不均匀,从而减少出现椭圆环黑色条纹现象。

80 MN reverse extrusion was conducted on the 2024 aluminum alloy T-shaped profiles,and the elliptical black stripes appear at the end of the profiles.The OM and EBSD were used to analyze the microstructure of stripe shape defects.It is shown that the edge zone of the black elliptical stripe is recrystallized,the transition zone is broken structure,and the inner part is deformed structure.In the three areas from the edge to the center,the contents of the grain boundary with an angle greater than 15°are:45%,19%and 48%,respectively.The content of large-angle grain boundary in the transition zone is significantly lower than those of the other two zones.The black stripes are formed by the fracture of the large-angle grain boundary,which is mainly due to the uncoordinated control of the extrusion temperature and the extrusion rate,resulting in uneven deformation in different areas of the profile section.By adjusting the extrusion die and extrusion temperature,the uneven deformation of different areas during the extrusion process can be avoided,and the phenomenon of elliptical black stripes can be reduced.