Explanation: The above statement is true. In an iron carbon alloy, the mechanical properties are dependent on the micro structure.

Explanation: Pearlite consists of alternate layer of ferrite and cementite in which cementite is harder and more brittle as compared to ferrite.

Explanation: Fine pearlite is harder than coarse pearlite, but coarse pearlite is more ductile than fine pearlite.

Explanation: The toughness of the steel decreases as we increase the carbon content and therefore 0.1% carbon which is lower than 1.5%, 0.2% and 2.5% is most tough among the options.

Explanation: Spherodite also consists of ferrite and cementite. In spherodite it cementite is present in a sphere structure in a matrix of ferrite.

Explanation: Bainite steels consists of α-Ferrite and cementite and have a finer structure which makes then stronger than pearlite steel.

Explanation: Among all the structure martensite has the strongest structure. It is the hardest and most brittle among the microstructure.

Explanation: If the carbon content in a steel is higher than 0.5 %, during quenching there can be a formation of quenching cracks.

Explanation: Tempered martensite has better ductility than martensite due to tempering. The hardness of the two is nearly the same.