The iPhone 6s is said to be using the same aluminum alloy found in the Apple Watch Sport, which will make it the toughest model yet.
Apple's next iPhone, presumable the iPhone 6s could be a little tougher than previous models, with the phone said to be making use of 7000 series aluminum alloy. This is the alloy currently found in the Apple Watch Sport, and Apple says that this alloy is 60% stronger than most aluminum. The new phone is also said to be ever-so-slightly thicker and taller.
This all comes from a research note from Ming-Chi Kuo of KGI Securities, by way of Macotakara (translated from Japanese):
The material is also changed to 7000 series aluminum. In addition to it, the width and height of the car will be wider and taller in about 0.15 mm for enhancement and its body will get thicker by 0.2 mm, which may be due to the changes to Force Touch display.
The iPhone 6s has previously been said to feature a very similar design to the iPhone 6 and iPhone 6 Plus, along with support for Force Touch. The phone will also reportedly have a new 12MP iSight camera, along with 2GB of RAM and a new color in rose gold.