Pitting of 2024 alloys prepared by spark plasma sintering using powders with different sizes

Correlation in microstructures of bulks and powders, pitting resistance and grain sizes for spark plasma sintered 2024 aluminum alloys has been studied. Results reveal the microstructures of bulk are resemble to powders. While the average grain sizes of bulks, which increase with raising powder size, are much smaller due to recrystallization. Corrosion in electrochemical tests increase with increasing grain size, suggesting a decreasing pitting resistance. Microscopy observation indicates pits initiate at intermetallic particles and the biggest depths range from 3.2 to 24.7 μm for A5 and A80. Mechanism analysis proves the stronger passivity of fine-grained samples enhances the corrosion resistance.