Chi Shuiqing, Deng Yunlai, Xu Xuehong, Guo Xiaobin
School of Materials Science and Engineering, Central South University, Changsha 410083, China.
Light Alloy Research Institute, Central South University, Changsha 410083, China.
Materials (Basel). 2020 Feb 1;13(3):650. doi: 10.3390/ma13030650.
The effect of 0.2 wt.% Zn addition on microstructure, age hardening and intergranular corrosion (IGC) properties of Al-Mg-Si alloy were investigated by scanning electron microscope, transmission electron microscope, hardness testing, and electrochemistry testing. The results showed that the addition of Zn can accelerate the transformation of GP zones into β″, and make the intragranular precipitates become smaller and with higher density. This is beneficial to the precipitation strengthening of the alloy, leading to obtaining higher hardness and enhancing the age hardening response. The peak hardness of the alloy with the addition of Zn is 125.8 HV which means increasing the hardness by 12.7 HV, compared with the alloy without Zn. However, the addition of Zn makes the precipitate-free zone (PFZ) of the alloy wider, and coarsens the grain boundary precipitates slightly, which result in the reduction of IGC resistance of Al-Mg-Si alloy. The maximum corrosion depth of the Zn-containing alloy is 121.3 μm in the peak age condition, which is 35.7 μm deeper than the alloy without Zn. The result of the potentiodynamic polarization curves also demonstrated the increase of IGC sensitivity. The corrosion current density of the alloy with added Zn is 0.595 μA/cm in the peak age condition, while that for the alloy without Zn is 0.199 μA/cm.
通过扫描电子显微镜、透射电子显微镜、硬度测试和电化学测试，研究了添加0.2 wt.% Zn对Al-Mg-Si合金微观结构、时效硬化和晶间腐蚀（IGC）性能的影响。结果表明，添加Zn可加速GP区向β″的转变，使晶内析出物变得更小且密度更高。这有利于合金的析出强化，从而获得更高的硬度并增强时效硬化响应。添加Zn的合金的峰值硬度为125.8 HV，与无Zn合金相比，硬度增加了12.7 HV。然而，添加Zn使合金的无析出带（PFZ）变宽，并使晶界析出物略有粗化，这导致Al-Mg-Si合金的抗晶间腐蚀性能降低。在峰值时效状态下，含Zn合金的最大腐蚀深度为121.3μm，比无Zn合金深35.7μm。动电位极化曲线的结果也表明了晶间腐蚀敏感性的增加。在峰值时效状态下，添加Zn的合金的腐蚀电流密度为0.595μA/cm²，而无Zn合金的腐蚀电流密度为0.199μA/cm²。
