Before revision: Furthermore, Due to the difference of density between the metals and intermetallics, the growth of the intermetallic layers causes reduction in volume, and therefore creates gaps in the metal near the interface between gold and aluminium.
After revision: Due to the difference of density between the metals and intermetallics, the growth of the intermetallic layers causes reduction in volume, and therefore creates gaps in the metal near the interface between gold and aluminium.