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利用硬度计(HV)、光学显微镜和透射电镜系统地研究了微量Zr(0.22%)对Al—5.0Zn-1.75Mg合金的沉淀过程、临界形核温度T′_c和显微组织参数的影响,并与Mn,Cr,Cu的影响进行了比较。结果表明,Zr能明显提高再结晶温度和细化晶粒,但无提高T′_c的能力。低温时效(T_a≤160℃),Zr有抑制GBP、促进MPt长大和提高HV的作用;但高温时效(T_a≥180℃)又有促进这两种参数急剧长大和强烈降低HV的作用。在选定的时效条件下(120—200℃),含Zr合金的PFZ均比无Zr合金窄。文中还讨论了Zr对Al-Zn-Mg合金的作用机理问题。
The effects of Zr (0.22%) on the precipitation process, critical nucleation temperature (T’_c) and microstructure parameters of Al-5.0Zn-1.75Mg alloy were systematically studied by means of hardness tester (HV), optical microscope and transmission electron microscope. The effects of Mn, Cr and Cu were compared. The results show that Zr can significantly increase the recrystallization temperature and grain refinement without any increase of T’_c. Under low temperature aging (T_a≤160 ℃), Zr could inhibit GBP, promote the growth of MPt and increase HV. However, the high temperature aging (T_a≥180 ℃) promoted the rapid growth of these two parameters and strongly reduced the HV. Under the selected aging conditions (120-200 ℃), the PFZ of Zr-containing alloys is narrower than that of Zr-free alloys. The mechanism of action of Zr on Al-Zn-Mg alloy is also discussed.