WSachse; 1/2012;M&AE 3272 - Supplementary Lecture Materials 1

The Fundamental Materials Triangle

Structure

Internal Structure and Composition of materials dictates their Properties

Material Properties determine the

Processing Operations that can be used

Processing Operations change a material’s

internal structure (“the material’s state evolves”)

Properties

M&AE 3272: Mechanical Propertyand Performance Laboratory

Processing

WSachse; 1/2012;

Classes of Materials

M&AE 3272 - Supplementary Lecture Materials 2

WSachse; 1/2012;

Material Size Scales

M&AE 3272 - Supplementary Lecture Materials 3

WSachse; 1/2012;

Mechanical Properties are Critical -Consequences can be catastrophic!

M&AE 3272 - Supplementary Lecture Materials 4

Failure of:• Bridges, Buildings, Structures• Aircraft• Medical Devices

Failure of F-15: The Air Force determined that the cause of the accident was a defective metal support beam . . .A failure of the upper right longeron, a critical support structure in the F-15C Eagle, caused the crash of a Missouri Air National Guard F-15C . . .The longeron didn't meet blueprint specifications. This defect led to a series of fatigue cracks in the right upper longeron which expanded under life cycle stress, causing the longeron to fail, thus initiating a catastrophic failure of the entire aircraft.

WSachse; 1/2012;

Properties of Metals:

M&AE 3272 - Supplementary Lecture Materials 5

Atomic Scale: Bonding• Metallic

Microstructure• Defects and Imperfections• Crystal grains; LamellaUseful Characteristics• Mechanical Properties• Electrical Conductivity• Huge Information and Experience Base• Machinability; FormabilityConcerns:• Fracture• Fatigue• Corrosion• Oxidation

WSachse; 1/2012;

Properties of Metals:

M&AE 3272 - Supplementary Lecture Materials 6

Aluminum – 20%Cu Aluminum – 33%Cu

Fe – 0.83%C: PearliteExample: Dislocations in Aluminumhttp://aluminium.matter.org.uk/content/html/ENG/default.asp?catid=71&pageid=1006363262

Atomic Scale: Bonding• Metallic

Microstructure• Defects and Imperfections• Crystal grains; LamellaUseful Characteristics• Mechanical Properties• Electrical Conductivity• Huge Information and Experience Base• Machinability; FormabilityConcerns:• Fracture• Fatigue• Corrosion• Oxidation

WSachse; 1/2012;

Properties of Metals:

M&AE 3272 - Supplementary Lecture Materials 7

Aluminum – 20%Cu Aluminum – 33%Cu

Fe – 0.83%C: Pearlite

Decarburized Original

Example: Dislocations in Aluminumhttp://aluminium.matter.org.uk/content/html/ENG/default.asp?catid=71&pageid=1006363262

Atomic Scale: Bonding• Metallic

Microstructure• Defects and Imperfections• Crystal grains; LamellaUseful Characteristics• Mechanical Properties• Electrical Conductivity• Huge Information and Experience Base• Machinability; FormabilityConcerns:• Fracture• Fatigue• Corrosion• Oxidation

WSachse; 1/2012;

Properties of Metals:

M&AE 3272 - Supplementary Lecture Materials 8

Atomic Scale: Bonding• Metallic

Microstructure• Defects and Imperfections• Crystal grains; LamellaUseful Characteristics• Mechanical Properties• Electrical Conductivity• Huge Information and Experience Base• Machinability; FormabilityConcerns:• Fracture• Fatigue• Corrosion• Oxidation

WSachse; 1/2012;

Aluminum and Steel Alloys:

M&AE 3272 - Supplementary Lecture Materials 9

Yield Strength depends on Composition

WSachse; 1/2012;

Effect of Alloying Additions and Grain Size:

Effect of alloying additions on the yield strength

of ferrite + pearlite structural steels.

1/2kd −+= 0σσ yM&AE 3272 - Supplementary Lecture Materials 10

Hall-Petch equation relating grain size to yield strength

of structural steels:

Effect of alloying additions on the yield strength

of ferrite + pearlite structural steels.

WSachse; 1/2012;

Steel: Hot and Cold Rolling and Microstructure:

M&AE 3272 - Supplementary Lecture Materials 11

Hot Rolling:Cold Rolling:

Yield Strength

Reduction of Area

Elongation

Tensile Strength

Reduction during Cold Working, %D

ecre

asin

g, %

Incr

easi

ng, %

WSachse; 1/2012;

The Magic of Steel (Part 1):Plentiful; Inexpensive; Easily processed to obtain materials of

varying strength

M&AE 3272 - Supplementary Lecture Materials 12

http://www.matter.org.uk/steelmatter/metallurgy/6_1_3_1.html

The carbon content at which the minimum austenite temperature is attained is called the eutectoid carbon content (0.68 wt. % C in case of themetastable Fe-C phase diagram.) The ferrite-cementite phase mixture of this composition formed during slow cooling has a characteristic appearance and is called pearlite and can be treated as a microstructural entity or microconstituent. It is an aggregate of alternating ferrite and cementite lamellae that coarsens (or "spheroidizes") into cementite particles dispersed within a ferrite matrix after extended holding at a temperature close to A1.

WSachse; 1/2012;

The Magic of Steel (Part 2):

M&AE 3272 - Supplementary Lecture Materials 13

Heat treatments of steel involve austenizing at temperature, followed by continuous cooling to room temperature.

• Ms - The highest temperature at which transformation of austenite to martensite starts during rapid cooling.

• Mf -The temperature at which martensite formation completes during rapid cooling.

CCT Diagram: AISI-SAE 1080 Steel

Time-Temperature-Transformation (TTT) DiagramExample: Iron-Carbon

http://www.matter.org.uk/steelmatter/metallurgy/7_1_2.html