(1. 中南大学 材料科学与工程学院，长沙，410083；
2. 中南大学 有色金属材料科学与工程教育部重点实验室，长沙 410083)
摘 要: 本文运用低钪和锆微合金化技术、力学和腐蚀性能测试及现代显微组织表征方法，在Al-5.98Zn-1.88Mg-0.41Cu合金棒材中添加0.10% Sc和0.09 % Zr(质量分数)，引入二次共格Al3(Sc1-xZrx)粒子，且避免了初生Al3(Sc1-xZrx)微米粒子生成。结果表明：共格粒子平均尺寸为15 nm，与基体完全共格，点阵错配度约为1.16%，可使挤压态、固溶态、T5和T6态Al-Zn-Mg-Cu合金屈服强度分别提升230 MPa(72.1%)、78 MPa(55.3%)、138 MPa(32.1%)和112 MPa(24.2%)，强化效果显著。理论计算表明，奥罗万析出强化为该粒子的主要强化机制。此外，尽管是钪添加量低，但生成的共格粒子仍可有效减小成品棒材中的大角度晶界比例，抑制晶界周围溶质原子区域的形成，可使欠时效、峰时效和过时效合金平行于挤压方向的抗剥落腐蚀等级由EC、EB和EA分别提高至EA、EA和PC级(垂直于挤压方向无晶间腐蚀敏感性)，并使欠时效、峰时效和过时效合金的晶间腐蚀深度分别由34.1 μm、29.1 μm和25.5 μm降至27.7 μm、24.5 μm和17.4 μm。
关键字: 铝合金；强化机制；腐蚀性能；共格粒子；显微组织
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China）
Abstract:In this paper, the effects of 0.10% Sc and 0.09% Zr (mass fraction) on microstructures and properties of extruded Al-5.98Zn-1.88Mg-0.41Cu alloy bars during preparation were investigated by microalloying technique of low-content Sc and Zr, mechanical and corrosion testing and microstructure characterization methods. The results show that low-content Sc and Zr exist in the form of secondary coherent Al3(Sc1-xZrx) particles, avoiding the formation of primary Al3(Sc1-xZrx) particles. The average size of coherent particles is about 15 nm, and they keep completely coherent relationship with matrix, with lattice misfit of about 1.16%. Those particles can improve the yield strength of extruded, solution treated, T5 and T6 alloys by 230 MPa (72.1%), 78 MPa (55.3%), 138 MPa (32.1%) and 112 MPa (24.2%), showing significantly strengthening effects. The theoretical calculation shows that Orowan precipitate strengthening is the main mechanism of coherent Al3(Sc1-xZrx) particles. In addition, although the addition of Sc is very few, the formed coherent Al3(Sc1-xZrx) particles still can effectively decrease the fraction of high angle grain boundaries of aged alloy bars, and can inhibit the formation of solute-atomic-free regions around grain boundaries, improving the EXCO rating from EC, EB and EA to EA, EA and PC, and decreasing the intergranular corrosion depth from 34.1 μm, 29.1 μm and 25.5 μm to 27.7 μm, 24.5 μm and 17.4 μm in under aged, peak aged and over aged Al-Zn-Mg-Cu bars parallel to the extrusion direction. This study provides a new way for simultaneously improving the strength and corrosion performance of alloys, moreover, the microstructural adaptation model for enhancing strength and corrosion resistance of Al-Zn-Mg-Cu alloy can provide scientific theoretical support for the development of high strength and high corrosion resistance aluminum alloy .
Key words: aluminum alloys; strengthening mechanism; corrosion performance; coherent particles; microstructures
