Microstructure–Property Link — Ferrite and Pearlite in Steel A steel whose microstructure consists predominantly of ferrite and pearlite will typically be:

Introduction / Context:
Mechanical properties of steels are dictated by their microstructures. Ferrite is a relatively soft, ductile phase, while pearlite is a lamellar mixture of ferrite and cementite offering higher strength and hardness than ferrite alone. Mild and medium-low carbon steels commonly exhibit a ferrite–pearlite mixture, leading to a desirable balance of ductility and strength for general engineering use.

Given Data / Assumptions:

• Microstructure contains ferrite plus pearlite (typical of low or medium-low carbon steel in the normalised or cooled state).
• No martensite, bainite, or strong precipitation hardening assumed.
• Room-temperature behavior considered.

Concept / Approach:
Ferrite contributes ductility and toughness. Pearlite contributes strength and some hardness due to the alternating ferrite–cementite lamellae. The combination yields steels that are not extremely hard but resist impact and bending reasonably well. Thus, the standout descriptor among the choices is “tough,” reflecting the ability to absorb energy before fracture, rather than “hard,” which would imply higher resistance to indentation typical of quenched/martensitic structures.

Step-by-Step Solution:
Identify properties of ferrite: soft, ductile → contributes toughness.Identify properties of pearlite: stronger and harder than ferrite but still reasonably ductile.Combine effects: overall moderate strength with good toughness; not especially hard.Select “tough” as the most appropriate single-word descriptor.

Verification / Alternative check:
Typical Charpy impact and elongation values for low-carbon ferrite–pearlite steels are higher than those of fully pearlitic or martensitic steels of similar carbon content, indicating better toughness.

Why Other Options Are Wrong:
Hard: excessive; martensitic or tempered martensitic structures are harder.Soft: incomplete; the presence of pearlite raises strength above very soft ferritic iron.Hard and tough: overstates hardness for this microstructure at comparable carbon levels.

Common Pitfalls:
Equating “strength” with “hardness”; they correlate but are not identical measures.

Final Answer:
tough