均匀化退火对5052含Er铝合金显微组织的影响

Effects of homogenization treatment on the microstructures of 5052-Er Al alloy

摘要:

利用光学显微镜、扫描电子显微镜、透射电子显微镜等手段研究了单级、双级和三级均匀化热处理对新型5052含Er铝合金显微组织的影响。研究结果表明,合金经560℃/30h高温均匀化热处理后,铸态组织中存在的非平衡共晶相大部分发生回溶,未溶的共晶相是Al₃Fe和Al-Fe-Er等富Fe相,第二级较低温的均匀化热处理有利于富Fe共晶相的球化和尺寸细化。研究结果还显示,均匀化制度显著影响析出相的析出行为。560℃/30h单级均匀化后的缓冷过程中有大量杆状β’(Al₃Mg₂)和球状Al₃(Er, Zr)、Al₃Zr相析出,但分布、尺寸很不均匀,析出相的总体积分数最高,为7.4%；第二级均匀化有利于细小均匀的Al₃(Er, Zr)、Al₃Zr纳米析出相形成,其中第二级均匀化温度为150℃时更有利于其弥散形核,析出相数量密度最高(20.3um_-1)、尺寸最细小(平均半径14nm)；采用三级均匀化处理可以在控制粒子尺寸的前提下,获得较高的数量密度。

Abstract:

The effects of single-step, two-step and three-step homogenization treatments on the microstructures of 5052-Er Al alloy were studied by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results showed that after 560℃/30h high temperature homogenization treatment, most of the non-equilibrium eutectic phases existed in the as-cast alloy dissolved, with the remaining phases being Fe-rich phases like Al₃Fe and Al-Fe-Er. The second step treatment performing at lower temperature was found to be beneficial to the spherization and refinement of the Fe-rich phases. The results also showed that homogenization treatment regimes had an obvious effect on the precipitation behavior of the fine precipitates. During the slow cooling process from 560℃/30h isothermally holding to room temperature, there were a large amount of rod β’(Al₃Mg₂) and spherical Al₃(Er, Zr) and Al₃Zr phases precipitating out of the matrix. The total volume fraction of the precipitates, 7.4%, was the highest among the four regimes conducted in this experiment. However, these precipitates distributed unevenly and their sizes differed greatly with each other. The second step treatment favored the formation of fine and homogenously distributed precipitates of Al₃(Er, Zr) and Al₃Zr. When the second step treatment was carried out at 150℃, the quantity density of the precipitates was the highest (20.3um_-1) with the finest particle size(average radius being 14nm). Three-step homogenization treatment could obtain a higher quantity density while maintaining a comparable particle size with that in two-step treatment.