3) Metastable phase.
Explanation: because on heating to high temperature and holding for long time Cementite breaks into Iron and Graphite....
An Equilibrium phase does not break into another phase within it's existing temperature range.

4) Ductility
Explanation: Ductility is mechanical property of a material by which a material can be drawn into thin wire.
Malleability: It is a mechanical property by which a material can be compressed to produce sheet or strip.

5) Gibbs free energy change
Explanation: Feasibility means possibility.
If Gibbs free energy change for a reaction is negative then the reaction would occur in forward direction.
If it is positive then the forward reaction would not occur.

6) Orthorhombic
Explanation: Cementite is an interstitial compund of ziron and carbon which contains 6.67 wt% carbon....
It has Orthorhombic Crystal structure.
Remember: Other important element in Metallurgy is Sulphur which has also Orthorhombic Crystal structure.

7) Diamagnetic
Explanation: Diamagnetic means the material or phase which doesn't have any magnetic property...
In simple word magnet doesn't attract the material or the phase at all.
Austenite is a Diamagnetic phase.
If a steel contains Austenite phase the magnet would not attract the steel.

8) Eutectic.
Explanation: On heating the following reactions prduces
Eutectoid: Solid 1+ Solid 2= Solid 3
Peritectoid: Soid 1= Solid 2+ Solid 3
Eutectic= Solid 1+ Solid 2= Liquid
Monotectic= Solid 1+ Liquid 2= Liquid 1

9) Fatigue failure.
Explanation: Fatigue means tiredness.
So fatigueue failure of material occurs when a repetative load is applied on a material for a large number of times.

10) Eutectoid
Explanation: Because in Iron-Cementite please diagram the this reaction takes place at any wt% of carbon.

Peritectic reaction occurs up to 0.5 wt% Carbon.
Monotectic reaction overlaps with peritectic part in the diagram.
Eutectic reaction occurs from 2.1 wt% to 6.67 wt % C according to Iron-Cementite phase diagram.