How Alloys Affects Physical Properties:

Nickel is an important alloying element.  Within concentrations of less than 5 percent, nickel will increase the toughness and ductility of steel without increasing the hardness.  It will not raise the hardness while added in these small quantities since it does not form carbides, solid compounds along with carbon.

Chromium in steel forms carbide which hardens the metal. A chromium atom might also occupy locations in the crystal lattice that will have the effect of rise hardness without affecting ductility. Further of nickel intensifies the effects of chromium, generating steel along with increased ductility and hardness.

Copper is quite same to nickel in its effects on steel. A Copper does not form carbide, but rise hardness through retarding dislocation movement.

Molybdenum forms complex carbide while added to steel. Since of the structure of the carbide, it hardens steel substantially, other than also minimizes grain enlargement. The Molybdenum tends to augment the desirable properties of both chromium and nickel.

Stainless steels are alloy steels holding at least 12 percent chromium. A significant feature of these steels is their resistance to various corrosive conditions.