Yes it can be welded.
they're low-grade cast aluminum.
use straight argon, not helium. (helium burns hotter).
TIG weld on LOW current. it's thin metal. acid dip first to leech out the oil otherwise it'll burn and pop and be a VERY messy and porous weld.
if you can't acid dip, then use a can of brakleen and clean the shit out of it, then prep with a stainless bristle wire brush.. make that metal shiny as fuck.
watch warp as well.. remember the stator core bolts to it.. shopuld warp if you're careful and fairly quick.
also, since it IS cast, preheat in an over after surface prep to 400*F weld, then stick back in the over and let it cool over the next 2-3 hours if you can.. drop 100* per hour.
good luck!
oh, and JB weld when will hold when done right as well.. again, surface prep is key. clean and scored with a wire brush or sandpaper to let the epoxy bond to something thats NOT glass-smooth!