Titanium alloy is a mixture of vanadium, chromium, nickel and aluminum. This material is three to four times stronger than stainless steel, which may make the iPhone lighter. The previous Huawei Mate XS 2 hinge used a titanium alloy frame, which greatly reduced the weight of the mobile phone.
Apple applied for a patent for semi-smooth metal last year, which may be used. This patent is a technical patent, which involves the combination of etching and chemical anodizing process to realize the required surface treatment. Apple said that the former is better at hiding metal defects, while the latter provides better protection.