I've had good success with aluminum welding. The whole gap would have to be opened up to allow material flow. It's hard to tell from the pics but it looks like the case may have to be split to do it right.

One thing the aluminum welder would do is drill a hole at the end of the crack to give that fracture a clean end point. If you're not going to weld it I would at least drill the end point if possible, it would probably prevent the fracture from growing.

At the very least, mark the ends of the fracture with some nail polish so that when you go back to inspect it later you can see how much it's grown.

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