Cooling curves provide information about phase changes that occur as materials cool over time. A cooling curve graphs the temperature of a material as it cools from the liquid state back to room temperature. For pure metals, the cooling curve shows a horizontal line at the freezing/melting point. For alloys, the initial and final phase change temperatures on the cooling curve are used to construct phase diagrams that map out the phases present at different compositions and temperatures. Cooling curves for different alloy compositions reveal information about solid solutions and eutectic systems.

1. COOLING CURVES
Prof. H. K. Khaira
Professor in MSME Deptt.
MANIT, Bhopal

2. Cooling Curve
• A cooling curve is a
graphical plot of the
changes in temperature
with time for a material
over the entire
temperature range
through which it cools.
• Cooling Curve for Pure
Metals is shown here.

3. Cooling Curve
• This is by far the most widely used experimental
method.
• It relies on the information obtained from the cooling
process.
• In this method, alloys with different compositions are
melted and then the temperature of the mixture is
measured at a certain time interval while cooling back
to room temperature.
• A cooling curve for each mixture is constructed and the
initial and final phase change temperatures are
determined. Then these temperatures are used for the
construction of the phase diagrams

4. Cooling curve for the solidification of
a pure metal
Under equilibrium
conditions, all
metals exhibit a
definite melting or
freezing point. If a
cooling curve is
plotted for a pure
metal. It will show a
horizontal line at
the melting or
freezing
temperature.

5. Cooling curve for a pure metal showing possible
undercooling.

6. Cooling curve for a solid solution.

7. Phase Diagram of alloy A+B

8. Series of cooling curves for different alloys in a completely
soluble system. The dotted lines indicate the form of the phase
diagram

9. Cooling Curves for Solid Solution
System

10. Cooling curve for the solidification of
an Eutectic Alloy
Under equilibrium
conditions, eutectic
alloys exhibit a
definite melting or
freezing point. If a
cooling curve is
plotted for a eutecti
alloy, It will show a
horizontal line at the
melting or freezing
temperature (eutectic
temperature).

11. Cooling Curve for Hypo and Hyper
Eutectic Alloys

12. THANKS