Metals Properties, Plasticity and Strengthening

Question 1

What is the equation for density?

Answer 1

density = mass/volume

Question 2

Why are metals generally the densest materials?

Answer 2

due to their close-packed atomic structures

Question 3

stiffness =

Answer 3

young’s modulus

Question 4

specific stiffness =

Answer 4

stiffness/density is important if mass is an issue

Question 5

What is the properties of metals - toughness?

Answer 5

toughness is the resistance to fracture (cracking)
- a measure of the resistance to crack it

Question 6

what material has the highest toughness?

Answer 6

metals have the highest toughness

Question 7

what materials have the lowest toughness?

Answer 7

ceramics have lower toughness

Question 8

where can’t low-toughness materials be used?

Answer 8

low toughness materials cannot be used in tension, but may be OK in compression. high toughness, you can start using these materials in tension

Question 9

why are metals useful structurally?

Answer 9

they are string (do not deform or break easily) so we can use them to support high loads
when they fail they tend to deform first, so we have a built-in safety factor

Question 10

What are dislocations?

Answer 10

dislocations happen in several different geometries (depends on the lattice type) but basic process is the same
to permanently deform a metal we must get dislocations moving, this occurs when we reach the yield strength.

Question 11

While dislocations move the metal can flow?

Answer 11

ductility, toughness

Question 12

What is edge dislocation?

Question 13

What is the screw dislocation?

Question 14

What is the mixed edge and screw dislocation?

Question 15

What is edge dislocation movement?

Question 16

What are some strengthening mechanisms?

Answer 16

The movement of dislocations means a metal is deforming
If we can block the motion of dislocations, we will have strengthened the material
Virtually all structural metals will need to have some strengthening