Thanks Murray, that is a surprise, but I suppose it explains why so many of them crack, and are repaired by pop-riveting sheet metal across to join it up. From memory most of the deck repairs we see here seem to be steel decks (probably on other brands of mower) and lots of them have plenty of welds by the time we hear about them.
If this one were mine I'd try riveting steel plates across the cracks, using two staggered rows of pop rivets on each side. It's important to make sure the rivet heads are on the aluminium side, so the other ends of the rivets won't pull through the holes by deforming the aluminium. An alternative that has worked well for me is to put a close-fitting stainless steel washer on the expanding end of each rivet before expanding it.
