chapter 7

Question 1

What influences the mechanical properties

Answer 1

The size of grain or average diameter influences the mechanical properties

Question 2

State 2 reasons that why grain boundary act as dislocation motion

Answer 2

1) because 2 grain are different orientation, dislocation passing into grain b must change its direction of motion this becomes more difficult as crystallographic disorientation increases

2) The atomic disorder in grain boundary region results in discontinuity of slip planes from one grain into another

Question 3

fine grain material is stronger than coarse because former has greater total grain boundary area to impede dislocation (T/F)

Answer 3

True

Question 4

grain size reduction does not improve strength and also toughness of many alloys (T/F)

Answer 4

false

Question 5

what is solid solution strengthen

Answer 5

alloying with impurity atoms that go into either substitutional or intestinal solid solution

Question 6

Does increase in concentration of impurity results in attend increase in tensile and yield strength

Answer 6

yes it does

Question 7

what type of stress do atom impose on surrounding lattice

Answer 7

larger atom impose compressive and smaller tensile

Question 8

In solid solution one or more solute atoms are incorporated into host metal (the solvent ) without forming a new phase (T/F)

Answer 8

T

Question 9

A material will lose its strength and sperate into pieces (T/F)

Answer 9

T

Question 10

Explain Ductile fracture

Answer 10

There is significant plastic deformation which initiates necking

if dimples it is ductile and many region around the fracture surface has ‘‘cup-cone” shape

Question 11

explain brittle

Answer 11

There is no strain/stretching around the crack. Crack happens very quickly and crack propagate perpendicular to the force. There are 2 propagations (1) intra granular fracture (2) trans granular fracture.