Nonferrous Alloys: Properties and Applications

6.1 Introduction to Nonferrous Metals and Alloys

Cost: Generally more expensive compared to ferrous alloys (refer to Table 6.1, not provided in transcript).
Useful Characteristics: Possess a wide range of useful characteristics and mechanical properties (refer to Tables 6.2, 6.3, and 6.5 to 6.10, with Table 6.3, 6.6, 6.7, 6.8, 6.9, 6.10 specifically discussed).
Modern Applications: The unique ranges of properties offered by nonferrous alloys are critical for many modern products that would otherwise be impossible or impractical to manufacture.
- Example: The Boeing $757$ engine, along with other key aircraft components, could not achieve required levels of power and efficiency without nonferrous alloys like nickel (Ni), titanium (Ti), and aluminum (Al) (refer to Figure 6.1, not provided in transcript).

6.2 Aluminum and Aluminum Alloys

Key Properties:
- High strength-to-weight ratio.
- Excellent chemical corrosion resistance.
- High thermal and electrical conductivity.
- Generally nontoxic.
- Reflective.
- Formable, machinable, and nonmagnetic.
Wide Range of Applications: Used in diverse sectors:
- Packaging (often disposable and recyclable).
- Structures.
- Transportation (e.g., aircraft components).
- Electrical applications.
- Consumer durables.
- Portable tools.
Available Forms (Wrought Products):
- Rolled.
- Extruded.
- Drawn.
- Forged.
- Cast ingots.
- Powders.
Hardening Mechanisms:
- Some wrought alloys can be hardened by cold-working.
- Some can be hardened by heat treatment.

Designation of Aluminum Alloys

Wrought Alloys (Four Digits + Temper Designation):
- First Digit (Major Alloying Element):
  - $1$ : Pure aluminum.
  - $2$ : Copper.
  - $3$ : Manganese.
  - $4$ : Silicon.
  - $5$ : Magnesium.
  - $6$ : Magnesium and Silicon.
  - $7$ : Zinc.
  - $8$ : Other elements.
- Second Digit (Alloy Modifications): Indicates specific modifications to the alloy.
- Third and Fourth Digits:
  - For $1xxx$ series (pure aluminum): Indicate the 99.xx ext{%} aluminum content.
  - For other series: Indicate other alloying elements and have no numerical significance.
Cast Alloys: Follow a similar pattern, but the first digit corresponds to major alloying elements differently.

Temper Designations (for both Wrought and Cast Alloys)

F: As fabricated (no subsequent treatment).
O: Annealed.
H: Strain-hardened.
T: Heat-treated.
W: Solution-treated (unstable state).
Numerical Suffixes: Numbers following the letter correspond to specific parameters and steps of the heat treatment processes.

Aluminum Production

Follows an ore extraction process similar to iron to produce aluminum oxide.
Aluminum oxide is then dissolved, and aluminum is extracted through electrolysis.
Electrolysis significantly contributes to the cost of aluminum production (approximately $1/3$ of the total cost).
Porous Aluminum: Can be manufactured with uniform microporosity, making it up to 37 ext{%} lighter than solid aluminum.

Table 6.3 - Engineering Properties of Aluminum Alloys (Sample Analysis)

Illustration of ultimate tensile strength, yield strength, and elongation for common alloys in annealed and treated states.
Observation: Strengths significantly increase (in some cases by more than a factor of $4$ ) in the treated state compared to the annealed state.
Trade-off: This increase in strength comes at the expense of elongation (ductility), which can decrease by more than a factor of $2$ in some cases.

6.3 Magnesium and Magnesium Alloys

Lightest Engineering Metal: Magnesium is known for its exceptionally low density.
Properties:
- Good vibration-damping capabilities.
- Available in both cast and wrought forms.
Safety Hazard: Magnesium oxidizes rapidly, posing a fire hazard, particularly during processing.
Production:
- Typically produced from seawater using an electrolytic reaction.
- Can also be extracted from mineral ore using thermal-reduction methods.
Market Position: Magnesium alloys often compete with aluminum alloys due to their similarly excellent levels of stiffness and strength per unit weight.

6.4 Copper and Copper Alloys

Historical Significance: Copper alloys date back to $4000$ B.C.
Properties:
- Somewhat similar to aluminum, with excellent conductivity.
- Good corrosion resistance.
- Substantially higher density than aluminum.
- Comparatively lower values of strength and stiffness per unit weight than aluminum.
Property Range: A wide range of properties is achievable through alloying and heat treatment (refer to Tables 6.6 and 6.7).
Most Common Alloys:
- Brass: Alloy of copper and zinc.
- Bronze: Alloy of copper and tin.
Other Alloying Elements: Copper is also alloyed with aluminum, beryllium, phosphor, nickel, and silver to create various specialized alloys.

Table 6.6 - Characteristics of Brass Alloys (Sample Analysis)

Shows ranges for ultimate tensile strength, yield strength, and elongation.
Observation: As the strength of a particular alloy increases, there is a corresponding decrease in elongation or ductility.
Lists typical applications for each alloy.

Table 6.7 - Characteristics of Bronze Alloys (Sample Analysis)

Shows ranges of characteristics (not explicitly described in transcript for this table, but assumed similar to brass).
Lists typical applications for each bronze alloy.

6.5 Nickel and Nickel Alloys

Role of Nickel as an Alloying Element: Nickel is a major alloying element that imparts strength, toughness, and corrosion resistance.
Common Applications of Nickel in Other Alloys:
- Stainless steels.
- Superalloys.
Applications of Nickel Alloys:
- High-temperature applications.
- Applications requiring exceptional corrosion resistance.
Alloying Elements Used with Nickel: Chromium, cobalt, aluminum, titanium, copper, iron, and molybdenum.
Named Alloys (Trademarked): Monel, Nichrome, Invar, among many others.
Properties as Alloys: Offer similar positive characteristics (strength, toughness, corrosion resistance) but generally at a relatively high density and weight.

Table 6.8 - Properties and Applications of Named Nickel Alloys (Sample Analysis)

Provides name, composition, strengths (ultimate tensile strength and yield strength), elongation, and applications for $6$ different nickel alloys.
Observation: Even higher-strength named nickel alloys exhibit substantial elongation values, indicating good ductility.

6.6 Superalloys

Primary Use: Primarily designed for high-temperature applications.
Key Resistances: Possess good resistance to:
- Corrosion.
- Fatigue.
- Shock.
- Creep.
- Erosion.
Primary Elements: The primary element may be iron, cobalt, or nickel (all superalloys contain significant quantities of nickel).
Major Alloying Elements: Nickel, chromium, cobalt, and molybdenum.
Other Alloying Elements: Aluminum, tungsten, and titanium.
Designation: Generally identified by trade names (almost entirely named, trademarked alloys), including:
- Incoloy.
- Hastelloy.
- Inconel.
- Nimonic.
- Rene.
- Udimet.
- Astroloy.
- Waspaloy.
Service Temperatures: Can sustain service temperatures as high as $1200^{ ceilcirc}C$ .

Table 6.9 - High-Temperature Properties of Superalloys (Sample Analysis)

Provides superalloy strengths (yield strength), elongation, and typical applications for $11$ different alloys, all measured at an elevated temperature of $870^{ ceilcirc}C$ (not room temperature).
Observations at $870^{ ceilcirc}C$ :
- Range of elongations: from 4 ext{%} to 125 ext{%}.
- Yield strength range: from $275$ megapascals (MPa) up to $760$ megapascals (MPa).
Primary Application: Almost all of these alloys are used for applications in jet engines, where high-temperature performance is critical.

6.7 Titanium and Titanium Alloys

Cost: Titanium is generally expensive.
Key Properties:
- High strength-to-weight ratio.
- High corrosion resistance.
- Can sustain service temperatures up to $550^{ ceilcirc}C$ .
Processing Challenges:
- Properties are extremely sensitive to small variations in alloying and residual elements.
- Processing is difficult and expensive, requiring extreme care to achieve desirable characteristics.
- These complexities contribute significantly to the high cost of titanium alloys.
Crystalline Structure:
- Beta-titanium: Body-centered cubic (bcc).
- Alpha-titanium: Hexagonal close-packed (hcp).
- Many other complex structures are possible with appropriate alloying and heat treating, nearly as diverse as ferrous alloys.

Table 6.10 - Composition, Strength, and Elongation of Titanium Alloys (Sample Analysis)

Provides data for $5$ alloy conditions at $2$ temperatures each ( $25^{ ceilcirc}C$ and $300^{ ceilcirc}C$ ).
Observation: The yield strengths drop much more significantly for some alloys than for others with an increase in temperature from $25^{ ceilcirc}C$ to $300^{ ceilcirc}C$ .

6.8 Refractory Metals and Alloys

Definition: A class of metals characterized by extremely high melting points.
Four Primary Refractory Metals: Molybdenum, Niobium, Tungsten, and Tantalum.
General Properties:
- High melting points.
- Very high service temperatures, ranging from $1100^{ ceilcirc}C$ to $2200^{ ceilcirc}C$ .
- Commonly used as alloying elements in other base metal alloys to enhance high-temperature performance.

Molybdenum

Properties: High stiffness, shock resistance, and conductivity.
Usage: The most commonly used refractory metal in engineering applications.
Limitation: Must be coated to avoid oxidation at high temperatures.

Niobium

Properties: Good ductility, formability, and oxidation resistance.
Usage: Fairly common in engineering applications and as an alloying element.

Tungsten

Properties:
- Highest melting point of any metal, at $3410^{ ceilcirc}C$ .
- High density.
- Poor ductility and resistance to oxidation.
- Service temperatures can exceed $1650^{ ceilcirc}C$ .
Applications: Used for balancing applications due to its high density.
Tungsten Carbide: A distinct material from tungsten alloys, it is a very common ceramic material for manufacturing tooling, typically with cobalt as a binder.

Tantalum

Properties:
- High melting point.
- Good ductility.
- Good corrosion resistance.
Limitations:
- High density.
- Poor chemical resistance above $150^{ ceilcirc}C$ .