Akuata Chijioke Kenneth, Gunawan Feliksianus Robby, Suwanpinij Piyada, Zander Daniela
Chair of Corrosion and Corrosion Protection, Foundry Institute, Division of Materials Science and Engineering, RWTH Aachen University, Intzestraße 5, 52072 Aachen, Germany.
The Sirindhorn International Thai-German Graduate School of Engineering (TGGS), King Mongkut's University of Technology North Bangkok (KMUTNB), 1518 Pracharat 1 Road, Wongsawang, Bangsue, Bangkok 10800, Thailand.
Materials (Basel). 2023 Jan 19;16(3):946. doi: 10.3390/ma16030946.
Microstructure optimization of Al-Zn-Mg-Cu-Zr aluminum alloys, particularly through recrystallization inhibition, for improved strength and corrosion resistance properties has been an important consideration in alloy development for aerospace applications. Addition of rare earth elements, sometimes combined with Cr, has been found to be beneficial in this regard. In this study, the role of a single addition of 0.1 wt.% Cr on microstructure evolution of an Al-Zn-Mg-Cu-Zr (7449) alloy during processing was systematically investigated by optical light microscopy, scanning electron microscopy, electron backscatter diffraction and scanning transmission electron microscopy. Susceptibility to localized corrosion after aging to T4, T6 and T76 conditions was evaluated by potentiodynamic polarization (PDP) measurements and an intergranular corrosion (IGC) test. A decrease in recrystallized fraction with 0.1 wt.% Cr addition was observed, which is attributed to the formation of Cu- and Zn-containing E (AlMgCr) dispersoids and the larger as-cast grain size. Moreover, the depletion of alloying elements from solid solution due to the formation of the Cu- and Zn-containing E (AlMgCr) dispersoids and Mg(Zn,Cu,Al) phase at its interface affects grain-boundary precipitation. The observed decrease in localized corrosion susceptibility with minor Cr addition is correlated with the microstructure and equally discussed.
对于航空航天应用的合金开发而言，通过抑制再结晶来优化Al-Zn-Mg-Cu-Zr铝合金的微观结构，以提高强度和耐腐蚀性，一直是合金开发中的重要考量因素。在这方面，已发现添加稀土元素（有时与Cr结合）是有益的。在本研究中，通过光学显微镜、扫描电子显微镜、电子背散射衍射和扫描透射电子显微镜，系统地研究了添加0.1 wt.% Cr对Al-Zn-Mg-Cu-Zr（7449）合金在加工过程中微观结构演变的作用。通过动电位极化（PDP）测量和晶间腐蚀（IGC）试验，评估了时效至T4、T6和T76状态后局部腐蚀的敏感性。观察到添加0.1 wt.% Cr后再结晶分数降低，这归因于含Cu和Zn的E（AlMgCr）弥散相的形成以及铸态晶粒尺寸较大。此外，由于在其界面处形成含Cu和Zn的E（AlMgCr）弥散相和Mg(Zn,Cu,Al)相，合金元素从固溶体中的贫化会影响晶界析出。观察到添加少量Cr后局部腐蚀敏感性降低，这与微观结构相关，并进行了同等讨论。
