Title: Aluminium - The material that changed the world

The Wright brothers chose wood and canvas as their structural construction materials because...

- spruce and ash have a high strength-to-weight ratio and canvas is a lightweigth material. (correct)
- the materials were readily available and affordable.
- the materials surfaces have little aerodynamic resistance.

Why was Aluminium still not used to construct planes yet, despite its affordability?

- Its low strength and easy deformability were unsuited for a lightweight structural material. (correct)
- Engineers prefered the well-proven, traditional construction materials.
- Although affordable, the metal was difficult to process into parts used in an airplane.

Background info: the stress-strain test.
This curve is the outcome of a typical stress-strain test. This test measures the amount of force (stress) needed to deform a material. The higher the stress necessary for a certain deformation (strain), the stronger the material.

What turned the weak and malleable Aluminium of the 20's into the strong structural material we use today?

- A new processing route resulted in enhanced properties. (correct)
- A new kind of Aluminium was discovered and mined.
- Better refining resulted in purer and hence stronger Aluminium.

The heat treatment by Alfred Wilm improved the strength of the Aluminium alloy because...

- it changed the alloy's atomic structure. (correct)
- it purified the alloy.
- it altered the composition of the alloy.

The mentioned applications use Aluminium because...

- its combination of properties match the specific requirements best and outperform alternative materials. (correct)
- it is a lightweigth and cheap material.
- it is the only material that offers the required properties (for example electrical conductivity).

Choose the correct statement.

This statement is not wrong – but it is not the one we are looking for.