According to information gleaned by investment bank JP Morgan Chase (via Macrumors), the high-end models of the iPhone 14 line scheduled for 2022 should be equipped with a titanium alloy chassis.
The strengths of titanium
These would be the first iPhones so equipped, knowing that the latest models to date are made of steel and aluminum. Titanium alloy is used for some versions of the Apple Watch Series 6. Titanium has a special strength that makes it resistant to scratches and bending. It's also as strong as steel and 45% lighter, as well as twice as strong as aluminum and only 60% heavier. Finally, it resists corrosion better than other alloys.