I can't say to what extent this is a real problem, but I can note that titanium has exceptionally poor thermal conductivity. Ti 6-4: 6.7 W/(m·K) Stainless st

I can't say to what extent this is a real problem, but I can note that titanium has exceptionally poor thermal conductivity. Ti 6-4: 6.7 W/(m·K) Stainless steel (18-8): ~16.5 W/(m·K) Aluminum 6061-T6: >150 W/(m·K) As engineering alloys go, in general, titanium is at the bottom of the pack for thermal conductivity. It's possible that this might make the body of the phone a poor heatsink and lead to localized hot spots. I'd think that the engineers at Apple have compensated for this, though. A thin internal copper or aluminum heatsink would be more than enough. But it's interesting that this titanium phone is experiencing thermal problems -- because that's the one problem you'd really expect to see with a titanium-bodied electronic device.