Lecture 10

Question 1

Metals make up _____ of the periodic table

Answer 1

75%

Question 2

Bonds in metals

Answer 2

A sea of moving valence e- in a network of positive ions

Question 3

Properties of metals

Answer 3

High thermal and electrical conductivity, malleable, lustrous.

Question 4

Normal metals (Al, Mg, Na) have ___ bonds

Answer 4

weak

Question 5

Transition metals have ____ bonds.

Answer 5

strong

Question 6

Coordination #

Answer 6

of nearest neighbors. Max is 12

Question 7

Crystallization

Answer 7

isothermal evolution with heat evolution

Question 8

Glass transition

Answer 8

gradual transition without heat evolution. L -> glass

Question 9

Difference between glass and crystal

Answer 9

Crystal is lattice, glass is not. Crystal has Tm, glass have a glass transition point

Question 10

Which lattices are the most common?

Answer 10

Cubic and hexagonal

Question 11

What are the 2 types of solid solution alloys?

Answer 11

Interstitial (smaller)

Substitutional (larger)

Question 12

Examples of Interstitial and Subsitutional

Answer 12

Int: C, N, H in steel
Sub: Ni in Cu and Fe (can be ordered or disordered)

Question 13

Grains

Answer 13

crystal with a orientation. All the crystals have the same chemical makeup, but are ordered differently.

Question 14

Defects in a material

Answer 14

Can only be perfect over an extremely small volume. All structures have defects, but this might not be detrimental to performance

Question 15

Classifications of defects

Answer 15

Point defects (0D)
Linear defects (1D)
Surface defects (2D)
Volume defects (3D)

Question 16

Point defects

Answer 16

interstitial/substitution. Has an impact on matter transfer and electrical conductivity

Question 17

Linear defects

Answer 17

local distortion of a perfect crystal lattice

Question 18

Small burger vector results in

Answer 18

more like to have a dislocation

Question 19

What is the burger vector

Answer 19

the extent of the defect

Question 20

Transfer phenom.

Answer 20

The core a dislocation is an increase in the diffusivity path

Question 21

Common 2D defects

Answer 21

Free surfaces, interphases, grain boundaries, twin boundaries, grain boundaries, twin boundaries, stacking faults

Question 22

Interphases

Answer 22

energy of the interphase depends on the structure of the phases and on their crystal orientation.

Question 23

Surface defects on high diffusivity paths

Answer 23

For atoms, diffusion
Heat conduction in some materials
Favor chemical reactivity
Fragile, preferential crack or corrosion site
Resist deformation

Question 24

Volume defects

Answer 24

• Pore and cavities
• Foreign particles and inclusions
• Non-desired phases

Question 25

3D Defects, impacts:

Answer 25

detrimental, concentrate stresses and initiate cracking/corrosion

Question 26

Defects - synthesis

Answer 26

entropy associated w/ defects, influence mech and transport properties, interact between each other. Volume effects are high cost.

Question 27

Lost wax casting hip implant

Answer 27

Mineral deposit (ore), metalic raw material in bluk form, stock shape, preliminary implant decide, final implant device, market

Question 28

Quality assurance (Ndt) Dimensions

Answer 28

]3D multi-sensor machine (optical and mechanic)

Question 29

Quality assurance (Ndt) Volumic defects

Answer 29

–X ray radiography station, –Ultra sound inspection, –fluorescent dye penetrant inspection plant ,

Question 30

Quality assurance (Ndt) Surface defects

Answer 30

–Eddy currents,

Question 31

Quality assurance (Ndt) Chemical analysis

Answer 31

– optical emission spectrometer, X-ray fluorescence spectrometry – carbon-sulphur analyser.

Question 32

Quality assurance (Ndt) Mechanical properties

Answer 32

-HRC and HV hardness machines

Question 33

Dental amalgams, an almost perfect PM process and product

Answer 33

``` Reaction: 59% powder 41 vol% Hg (liquid) Powder : 60%Ag, 30 Sn,10 Cu Mercury desintegrates the particles and reacts to form Ag3Hg4, , causing the setting of the amalgam No volume change! ```