Ageing is a heat treatment process used in plain steels The

Ageing is a heat treatment process used in plain steels. The particles used for dispersion strengthening must be softer than the matrix. The recrystallization temperature is generally between 0.6 to 0.8 the melting point of the material. A steel should be used below its ductile-to-brittle transition temperature. Polymers have a ductile-brittle transition temperature The maximum hardness during precipitation hardness is obtained when the precipitates are fully coherent.

Solution

1..

False: Ageing is not a heat treatment process. Like due to Strain Agening yield strength will increase at the cost of ductility.

2....

True.

The matrix material acts as a medium to transfer the load to the fibers, which carry most off the applied load. So matrix strength should be higher than the fibers.

3.....False

Recrystallization..Temerature at which 50% of recrstallization occur in 1 hr.

For Pure Metals Recrystallization Temerature is 0.3 to 0.4 of Melting Point. And

For alloys it is 0.5 of Melting Point temperature.

4...............

True.

If temp is low some metals converts from ductile to brittle. For steel it can be around 0 deg.

5......

True.

At low temerature many Plastics become brittle.

6.....

True.

Maximum strengthening is obtained when precipitate is small and coherent with matrix.