Understanding Work Hardening and Heat Treatment

What is the main characteristic of work hardening (strain hardening) in metals?

• It increases ductility and makes metals easier to shape.

• It increases strength but reduces ductility.

• It decreases the number of dislocations in the crystal lattice.

• It only occurs below the elastic limit.

Which law no longer applies once a metal has exceeded its elastic limit and undergoes plastic deformation?

• Newton’s First Law

• Ohm’s Law

• Hooke’s Law

• Boyle’s Law

What happens to dislocations in the crystal lattice during work hardening?

• They decrease in number.

• They remain unchanged.

• They increase, making further deformation harder.

• They disappear completely.

Why does further deformation become more difficult during work hardening?

• The metal becomes more elastic.

• Dislocations pile up at grain boundaries, creating back-pressure.

• The temperature of the metal decreases.

• The grain size increases.

Which of the following is NOT a purpose of heat treatment after work hardening?

• To restore ductility

• To increase residual stress

• To modify mechanical properties

• To make metals workable again

Which heat treatment process is specifically used to reduce residual stress in metals?

• Quenching

• Annealing

• Stress relieving

• Normalising

What is the main effect of annealing on a metal?

• It increases hardness.

• It softens the metal, improving ductility.

• It makes the grain structure coarser.

• It increases residual stress.

Which heat treatment process involves rapid cooling to increase hardness?

• Normalising

• Quenching

• Annealing

• Stress relieving

What is the main reason excessive work hardening can make further shaping of a metal impractical?

• The metal becomes too soft.

• There is a risk of tearing.

• The metal becomes more ductile.

• The grain boundaries disappear.

Which heat treatment process is used to refine grain structure for more uniform properties in metals?

• Annealing

• Quenching

• Normalising

• Stress relieving