However,the thickening of IMC layer is not large in terms of long post weld time.
It should be pointed out that optical micrograph may not resolve IMC mixed area
due to their limitation in resolution, even though significant diffusion crosses the interface through IMC layer. A recent study by Rathod on joining of AA5052 and low carbon steel concluded that with the increase of total thickness of the intermetallic layer, the amount of Al-rich IMC in it increased and the amount of Fe-rich IMC decreased, which resulted in drastically reducing the joint strength. Therefore,
more detailed investigation need to be conducted to
interpret the increased peak load with longer post weld time.