By the 1950s, Bentley refined its aluminum alloy even further with the inclusion of silicon and magnesium. This image taken from Raw to Ready: Bentley demonstrates how while aluminum by itself is very soft, if you add small amounts of silicon and magnesium into it, the magnesium and silicon combine making small particles that make the metal harder. This is the key to making it useful in an engine block. This combination is so strong that Bentley is able to use it for their V8 engine block.