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通过使用光学显微镜、扫描电镜、透射电镜及X射线衍射等手段研究一种新型Er、Zr微合金化Al-Zn-Mg-Cu合金在均匀化过程中的显微组织演变。结果表明:铸态合金组织存在严重的偏析,此时合金中含有大量的T(AlZnMgCu)、S(Al_2CuMg)和Al_8Cu_4Er相,这些初生相大量偏聚于晶界。随着在465°C单级均匀化处理的进行,第二相含量大幅度降低,可熔的T相和S相会逐步地熔入基体,但Al8Cu4Er相不能完全消除,仍有少量残留。相对于单级均匀化工艺,合金在双级均匀化处理时不仅能够消除铸态合金偏析组织,而且能够析出大量细小弥散分布的L1_2结构的Al_3(Er,Zr)相。结合均匀化动力学分析,可以得出合金合理的均匀化热处理制度为(400°C,10 h)+(465°C,24 h)。
The microstructure evolution of a new Er, Zr microalloyed Al-Zn-Mg-Cu alloy during homogenization was investigated by means of optical microscope, scanning electron microscope, transmission electron microscopy and X-ray diffraction. The results show that there is a serious segregation of the as-cast alloy structure. At this time, the alloy contains a large amount of T (AlZnMgCu), S (Al2CuMg) and Al_8Cu_4Er phases. With the single-stage homogenization at 465 ° C, the content of the second phase is drastically reduced and the fusible phases T and S gradually fuse into the matrix, but the Al8Cu4Er phase can not be completely eliminated with a small amount of residual. Compared with the single-stage homogenization process, the alloy can not only eliminate the as-cast alloy segregation structure but also precipitate a large amount of finely dispersed L1_2 Al3 (Er, Zr) phase during the two-stage homogenization. Combining with the homogenization kinetic analysis, it can be concluded that the reasonable homogenization heat treatment of the alloy is (400 ° C, 10 h) + (465 ° C, 24 h).