Chapter 14, Problem 42A

Interpretation Introduction

Interpretation:

The fact that the properties of a metal get modified by alloying the metal with some other substance needs to be explained. The change in the properties of iron due to producing various types of steels needs to be described.

Concept Introduction:

Alloy is a mixture of different metals and has metallic properties. A metal is combined with one or more metals to form an alloy.

There are two types of alloys-

1. Substitutional alloy
2. Interstitial alloy

Explanation of Solution

When small amounts of one or more metals are introduced to the host metal, the properties of host metal have been improved than the pure one. Because introducing a metal atom to a lattice of another metal usually increase the strength of the lattice as they help to prevent the lattice from rupturing along lattice lines.

Steel is an interstitial alloy of iron and carbon because the size of carbon is much smaller than iron. In steel, the smaller size carbon atoms occupy the interstitial site created between two iron lattices. Pure iron is relatively soft, ductile, and malleable as iron particles are not tightly packed result in formation of holes in interstitial site. When carbon atom is introduced in the iron crystal, the resulting mixture or alloy becomes harder, stronger, and less ductile than the pure iron. Depending upon the percentage of carbon atom present in the alloy, the properties of alloy varied. When chromium or nickel is introduced in steel with iron and carbon, the resistance of the steel against the corrosion, increases.