Intergranular corrosion of spark plasma sintered 2024 aluminum alloy at different heat treatment states

2024 aluminum alloys were consolidated by using spark plasma sintering(SPS) method,and then heat treated by solid solution treatment(SST) and aging treatment(AT) procedures.The average grain size of bulk samples sintered with 5,20 and 50 μm powders was 3.72,4.73 and 8.11 μm,respectively.The difference between the average grain size and original powder size was attributed to the recrystallization during short sintering process.The number of the inclusion phases in these samples decreased after SST and increased after subsequent AT.Besides,it was observed that intergranular corrosion(IGC) cracks initiated from stable pits due to the electrochemical inhomogeneity between the intermetallic particles(IMPs) and the aluminum matrix(176.02,110.83 and 164.80 mV for as-SPS,as-SST and as-AT samples,respectively).Besides,the cracks would propagate along the grain boundaries(GBs) and bypass the IMPs at GBs during propagation.It was revealed that the sample after SST presented the best IGC resistance,and this was ascribed to the reduce of IMPs,both in size and number.