
390 Engineering Materials Technology
concern. The coefficient of expansion a is defined as being the change in length
per unit length per degree change in temperature, i.e.
change in length
original length x change in temperature
Typical values for the coefficient of linear expansion in the temperature region
0° to 100°C are: aluminium and its alloys 22-24 x
10
~
6
K"', copper and its
alloys 16-20 x 10~
6
K
-1
, steels 10-12 x 10~
6
K
_1
, magnesium and its alloys
25-27 x 10" K"
1
, nickel and its alloys 11-13 x 10~
6
K"\ titanium and its
alloys 8-9 xlO^K"
1
.
18.10 Selection for dimensional conditions
The requirement for a particular dimensional condition ...