1. (a) How are the following properties of iron affected when carbon is alloyed with it?

Illustrate your answer with reference to the microstructure of the steel.

- hardness
- strength
- ductility.

(b) What percentage of carbon produces the strongest plain carbon steel?

2. The ultimate tensile strength of a material was tested using 10 samples.

The results of the tests were as follows :

711 N mm^-2, 732 N mm^-2, 759 N mm^-2, 670 N mm^-2, 701 N 765 N mm^-2, 743 N mm^-2, 755 N mm^-2, 715 N mm^-2, 713 N mm^-2.

(a) Determine the mean and standard deviation of these results.

(b) Express the values found in (a) in GPa.