When it comes to designing smartphones, there are a huge number of competing factors including the size, weight, cost and the materials. More and more manufacturers are switching to increasingly exotic-sounding materials for smartphones and Samsung's recent switch to aluminum for the flagship S-series of Android smartphones highlights the trend. HTC and Apple have been using metal construction in their devices for a number of years now and surely, building a 'phone from aluminium is the same as building a 'phone from aluminium, right? Wrong. Some of the engineering compromises include designing an antenna system whereby the various radios inside a smartphone - and there are many, including but not limited to 2G, 3G, 4G, WiFi, Bluetooth, NFC and infrared - are able to function properly without interference regardless of how the customer holds it. Another compromise concerns the ease of manufacturing and repairing the device, and another concerns the strength of the material and of course the design itself.
As it happens, there are many, many different grades of aluminium. Currently, most metal-built smartphones are constructed from aluminum 6063, a part of the aluminum 6000 family. The aluminum 6000 series is constructed with magnesium and silicon and compared with other series of aluminums, are considered easy to machine and are weldable. The 6000 series of aluminum alloy may also be hardened, but not as tough as aerospace-grade aluminum alloys (2000 or 7000 series). A number of industry experts are predicting that Apple will be switching from their current aluminum alloy construction to using a tougher material, presumably to avoid their 'phones from bending (did they bend, did anybody see an iPhone 6 Plus bend?). One of the materials that's been rumored is aircraft grade from the aluminum 7000 series, reckoned to be around 1.6 times stronger than Apple's current aluminum chassis designs. Samsung also opted for aluminum 6013 for the Galaxy S6, which it believed would work well with Gorilla Glass 4 and is around 1.5 times stronger than aluminum 6063 (and 1.2 times more scratch-resistant, too). Aluminum 6013 is used in the aerospace, automobile and yachting industries.
Writing of Gorilla Glass 4, this fourth generation toughened and scratch-resistant glass is some 25% thinner but tougher than the third generation Gorilla Glass, which in itself is thinner and tougher than the second generation material. Gorilla Glass is reinforced by the raw material being immersed in a hot potassium salt ion-exchange bath at a temperature of approximately 750 degrees, which causes the smaller sodium ions in the glass to be replaced by potassium ions in the salt bath. The potassium ions are larger than the sodium ions and create a surface layer of high residual compressive strength, which makes the glass surface very strong and with high crack resistance. Another high tech glass material is Sapphire Glass; Kyocera and Huawei have already started using Sapphire Glass and Apple are very likely to do so for the next generation device. Sapphire Glass is very strong but is vulnerable to scratching; Corning, the manufacturer of Gorilla Glass, is believed to be working on a combination of Gorilla Glass and Sapphire Glass so that the product has the best of both worlds: very high strength combined with excellent scratch resistance.
It's entirely possible that manufacturers will use alternative materials for the construction of smartphones and tablets going forwards, but as technologies are evolved, design and manufacturing processes are refined, it's clear that the device we buy in a few years time is likely to be quite different in construction from the device we may be buying today.