Metallurgical Engineering Mock Interview Questions & Practice

What is the difference between BCC and FCC crystal structures in terms of atomic packing efficiency?

Key points to cover:

• FCC has a higher atomic packing factor (~74%) than BCC (~68%)
• FCC packs atoms more densely
• Influences density, ductility, and how the metal deforms

What is tempering, and why is it typically performed after quenching a steel?

Key points to cover:

• Reheating a quenched (hardened) steel below its critical temperature
• Then cooling
• Reduces brittleness and stress, trading hardness for toughness

What is the Hall-Petch relationship, and what does it describe about grain size and strength?

Key points to cover:

• An inverse relationship between grain size and yield strength
• Smaller grains generally result in higher yield strength
• Attributed to grain boundaries impeding dislocation movement

What is the difference between crushing and grinding in ore comminution?

Key points to cover:

• Crushing: first, coarser size-reduction stage
• Reduces large rocks into smaller fragments
• Grinding: finer size-reduction using rotating mills with grinding media

What is roasting in pyrometallurgy, and what is its basic purpose?

Key points to cover:

• A thermal treatment in the presence of air/oxygen
• Applied to an ore (often sulfide) before the main extraction step
• Converts the ore into a form more suitable for reduction

What is the difference between acid leaching and alkaline (basic) leaching?

Key points to cover:

• Acid leaching: uses an acidic solution (e.g. sulfuric acid)
• Effective for many oxide/sulfide ores
• Alkaline leaching: uses a basic solution, often for gold or gangue-sensitive ores

What is the difference between the Brinell, Rockwell, and Vickers hardness testing methods?

Key points to cover:

• Brinell: uses a hardened steel/carbide ball indenter
• Rockwell: measures indentation depth under a fixed load
• Vickers: uses a diamond pyramid indenter, suited to a wide hardness range

What is the endurance limit (fatigue limit) of a metal, and what does it represent?

Key points to cover:

• The maximum stress amplitude below which fatigue failure
• Will not occur regardless of the number of cycles
• Applicable mainly to certain materials like steel

What is galvanic corrosion, and under what condition does it occur?

Key points to cover:

• Accelerated corrosion of one metal
• When two dissimilar metals are in electrical contact in an electrolyte
• The more active (anodic) metal corrodes preferentially

What is Hooke's Law, and within what range of deformation does it apply?

Key points to cover:

• Stress is directly proportional to strain
• Proportionality constant is the material's modulus of elasticity
• Applies only within the elastic limit

What is a bending moment diagram, and what information does it provide?

Key points to cover:

• A graphical representation of bending moment along a beam
• Provides the location and magnitude of maximum bending stress
• Essential for beam design

What is stress concentration, and what commonly causes it in a machine component?

Key points to cover:

• A localized increase in stress at a geometric discontinuity
• Well above the average stress in the surrounding material
• Commonly caused by abrupt changes in cross-section or geometry