ME Processing and Manufacturing

Question 1

In metal casting, porosity defects are primarily caused by:

Accepted Answer

Gas entrapment or shrinkage during solidification

Answer

Porosity in castings arises from dissolved gases released during solidification or from volumetric shrinkage as metal contracts when changing from liquid to solid.

Question 2

Hot working of metals is performed above the recrystallization temperature primarily to:

Accepted Answer

Allow dynamic recrystallization, maintaining ductility at high deformation levels

Answer

Hot working enables large deformations with lower forces because recrystallization continuously replaces deformed grains with new equiaxed grains, preventing work hardening.

Question 3

Which powder metallurgy step bonds metal powders into a dense solid part using heat and/or pressure below the melting point?

Accepted Answer

Sintering

Answer

Sintering heats compacted powder to typically 70-90% of the melting point, activating diffusion that bonds particles and densifies the compact without melting.

Question 4

The purpose of annealing a cold-worked metal is to:

Accepted Answer

Restore ductility by reducing dislocation density via recovery and recrystallization

Answer

Annealing heats cold-worked metal to allow recovery (stress relief) and recrystallization (new strain-free grain formation), restoring ductility and reducing hardness.

Question 5

Investment casting (lost-wax casting) is preferred for complex shapes because:

Accepted Answer

It uses an expendable wax pattern to produce intricate, near-net-shape parts

Answer

In investment casting, a wax pattern is coated with ceramic slurry, the wax is melted out, and metal is poured into the cavity, allowing complex geometries with excellent surface finish.

ME - Materials Engineer Practice Test

ME - Materials Engineer Practice Test

ME Processing and Manufacturing