Zn和Mg元素对高Zn含量Al-Zn-Mg-Cu合金铸锭及其均热态组织的影响  

Microstructure of Semicontinuous Casting Ingot and Homogenization of High Zinc-Containing Al-Zn-Mg-Cu Alloys with Zn and Mg Additives

作　　者：王杰[1] 张永安[1] 范云强[1] 金龙兵[1] 李锡武[1] 李志辉[1] 

机构地区：[1]北京有色金属研究总院有色金属材料制备加工国家重点实验室,北京100088

出　　处：《稀有金属》2016年第11期1081-1087,共7页Chinese Journal of Rare Metals

基　　金：国家重点基础研究发展计划项目(2012CB619504);国家自然科学基金项目(51274046)资助

摘　　要：以Al-9.2Zn-2.0Mg-1.8Cu合金为基础合金,共设计了3种化学成分的合金,采用金相显微镜(OM)、扫描电镜(SEM)、X射线衍射(XRD)、差热分析(DSC)等手段,同时结合Pandat热力学计算,研究了Zn和Mg元素对半连续铸造高Zn含量Al-Zn-Mg-Cu合金铸态和均匀化组织的影响。结果表明:合金铸态组织中第二相主要包括非平衡共晶(AlZnMgCu)四元相、大量细小的短棒状MgZn_2相以及很少量的富Cu相;提高Zn和Mg元素的含量均会导致合金铸态组织中非平衡共晶相数量及非平衡共晶相厚度的增加,且在高Zn含量Al-Zn-Mg-Cu系合金中Mg元素影响更大,这与热力学计算结果基本一致。各合金经过470℃/24 h均匀化处理后,Al-9.2Zn-2.0Mg-1.8Cu合金回溶完全,Mg和Zn元素含量更高的合金回溶不充分,组织中仍存在一定数量的(AlZnMgCu)四元相,其中,在高Zn含量Al-Zn-Mg-Cu合金中Mg元素的增加尤其不利于均匀化的进行。Based on Al-9.2Zn-2.0Mg-1.8Cu alloy, the effects of alloying elements Zn and Mg on the microstructure of semi-continuous casting ingot and homogenization treated state of high zinc-containing Al-Zn-Mg-Cu alloys were investigated using optical microscopy（OM）, X-ray diffraction analysis（XRD）, differential scanning calorimeter （DSC） and scanning electron microscopy （SEM） combined with Pandat thermodynamic calculation. The results showed that the as-cast microstructure mainly consisted of nonequilibium eutectic phase, bulk of tiny MgZn2 and very few Cu-rieh phases. Moreover, it appeared that more amount of nonequilibium eutectic phase and thicker grain boundary phase would be found in researched alloys with higher Zn and Mg contents. The content of MgZn2 was mainly controlled by the elements of Zn and Mg, and Mg had a greater impact on MgZn2 phase in the high zinc-containing Al-Zn-Mg-Cu alloys, which was consistent with the thermodynamic calculation results. As for alloys with different compositions homogenized at 470 ℃ for 24 h, it was found that there were still a certain number of nonequilibium phases existed in alloys with higher Zn and Mg contents, while there was no nonequilibium phase found in the base alloy. In particular, the increase of amount of Mg element would be more harmful to the homogenization process in high zinc containing Al-Zn-Mg-Cu alloys.

关 键 词：Zn Mg元素 Al-Zn—Mg—Cu合金 铸态组织 均匀化热处理 

分 类 号：TG146.2[一般工业技术—材料科学与工程] TG113[金属学及工艺—金属材料]