Zn/Mg比对7003铝合金挤压型材组织与性能的影响

Effect of Zn/Mg Ratio on Microstructure and Properties of 7003 Aluminum Alloy Extruded Profile

摘要: 中高强型Al-Zn-Mg合金的腐蚀性能及力学性能的综合调控在工程应用上尤为重要。本文以不同Zn/Mg比的7003铝合金挤压型材为对象，在(Zn + Mg)总量约为6.6 wt.%的冶金质量下，通过室温拉伸、晶间腐蚀等分析测试方法，并采用扫描电子显微镜(SEM)和透射电子显微镜(TEM)分别对微米级第二相和纳米级时效析出相进行观察，研究了Zn/Mg比对力学性能和抗晶间腐蚀性能的影响规律。结果表明：在120℃的峰值时效状态下，Zn/Mg比从11.4降至6.1，7003-T6铝合金中η’相分布密度增加，使抗拉强度和屈服强度分别提高34.1%和47.4%，而第二相体积分数的减少及PFZ的窄化使得延伸率仅降低了1.1%。加之晶界析出相从连续转变为断续分布的状态，降低了7003铝合金的晶间腐蚀倾向性。

Abstract: The comprehensive regulation of the corrosion and mechanical properties of medium-high strength Al-Zn-Mg alloys is particularly important in engineering applications. In this paper, 7003 aluminum alloy extruded profiles with different Zn/Mg ratios are taken as the object. At the metallurgical mass of 6.6wt.% of total (Zn + Mg), the analysis and test methods such as room temperature tensile and intergranular corrosion are adopted. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to observe the microscale second phase and nanoscale aging precipitated phases, respectively. The influence of Zn/Mg ratio on mechanical properties and resistance to intergranular corrosion was studied. Results show that under the peak aging condition at 120˚C, the Zn/Mg ratio decreases from 11.4 to 6.1, the distribution density of η’ phase in 7003-T6 aluminum alloy increases, which increases the tensile strength and yield strength by 34.1% and 47.4%, respectively. And the reduction of the volume fraction of the second phase and the narrowing of the PFZ reduced the elongation by only 1.1%. In addition, the grain boundary precipitation phase changes from continuous to discontinuous distribution, which reduces the tendency of intergranular corrosion of 7003 aluminum alloy.