If so why does an aluminum bend or get nicked or break quickly?
MPCheu is on the right track. Bending and getting nicked so it will break quickly are different things than strength and there are many different types of strength. Previous answers are correct regarding specific strength, say yield strength per unit mass because Al is much less dense than iron (the primary component of steel). It is also worth noting that there are many different types of steels and any one of these steels can have a very large range of mechanical properties. Same is true of aluminum alloys. The reason most airplanes are made using Al alloys is all about this specific strength and it is the same reason Al alloys are being replace by composite materials which have even higher specific strengths, densities about the same as Al but with much higher strengths. hope this helps
Steel has roughly twice the strength of aluminum but is three times as a heavy. So, you can build an aluminum component that is stronger than a similar weight steel component. But, if you were looking at two similar sized components, then the one made from steel would be stronger.
NO! You should ask yourself why Tank built with steel rather than using aluminum.
It depends on how you set the criteria of comparison. If you go by volume, Aluminum isn't stronger. That's why a steel can is stronger than one of similar size and thickness. If you go by weight, aluminum is said to be stronger. Let's say we were looking to create a wall, spec'ed to a particular height and width, and just thick enough to hold back a given PSI of pressure. The aluminum one would have to be thicker to have the strength to hold back the pressure, but it'd be lighter than the steel equivalent. Also, the ease by which a material can be nicked isn't an indicator of strength but of hardness. Harder, isn't necessarily stronger.
