Chapter 3 part 1: Classification of Aluminum Alloys

Question 1

Two classified groups of commercial alloys

Answer 1

Cast: Sand, permanent mold, diecast
Wrought: Deformed state (extruded, forged, rolled, pressed)

Question 2

What two main characteristics do casting alloys require?

Answer 2

Fluidity (for mold-filling)
Hot-crack resistance (hot strength to not crack while cooling)

Question 3

What is casting alloy fluidity related to?

Answer 3

Inversely proportional to freezing range Delta T (Ts - Tl)

Question 4

At what compositions is fluidity best seen in alloys?

Answer 4

Best seen at compositions that solidify at constant temperatures (pure metals and eutectics)

Question 5

What is casting alloy hot-strength related to?

Answer 5

It is related to the number of hot phases
Too close to eutectic may reduce ductility and toughness though

Question 6

What main characteristics do wrought alloys require?

Answer 6

Ductility and low strength at high (working) temperatures
High strength at lower temperatures
Ideally solid solutions at high temperatures and dilute alloys with low wt% of second phase at low temperatures

Question 7

When is strength highest for wrought alloys?

Answer 7

Near the eutectic
However, this reduces ductility, plasticity, and formability

Question 8

When is ductility and low hot-strength highest for wrought alloys?

Answer 8

Alloys near the solid solubility limit at high temperatures

Question 9

How are wrought alloys further subdivided?

Answer 9

1) non heat-treatable
2) heat-treatable

Question 10

Where is the limit between heat-treatable and non heat-treatable wrought alloys?

Answer 10

The solid solubility limit at room temperature
Levels above this limit are needed for adequate age hardening response