Reading Assignment:
- 7.1 Introduction to Nonferrous Metals and Alloys
- 7.2 Copper and Copper Alloys
- 7.4 Zinc-Based Alloys
- 7.5 Magnesium
- 7.6 Titanium
- 7.7 Nickel
- 7.8 Superalloys
- 7.9Lead and Tin
- 7.10 Some Lesser Known Metals and Alloys
- 7.11 Metallic Glasses
- 7.12 Graphite
Additional Reading
- TA479.S7 S677 1994 Stainless Steel
- TA480.A6 A6177 1993 ASM Specialty Handbook: Aluminum
- TA480.L4 G87 2000 Engineering Properties and Applications of Lead Alloys
- TA480.Z6 P67 1991 Zinc Handbook
- Copper and Copper Alloys
- Copper Tube Handbook
- Storing Drinking-water in Copper pots Kills Contaminating Diarrhoeagenic Bacteria
- Engineering Properties and Applications of Lead Alloys
- Magnesium and Magnesium Alloys
- Nickel, Cobalt, and Their Alloys
- Titanium and Titanium Alloys: Fundamentals and Applications
- Machining Titanium
- 10 Tips for Machining Titanium
Outline
Usage of nonferrous metals and alloys has increased due to technology
Possess certain properties that ferrous materials do not have:
- Resistance to corrosion
- Ease of fabrication
- High electrical and thermal conductivity
- Light weight
- Strength at elevated temperatures
- Color
- Changes in Automotive Material Usage
Copper and Copper Alloys
- General properties and characteristics
- Backbone of the electrical industry
- Base metal of a number of alloys such as bronzes and brasses
- High electrical and thermal conductivity
- Useful strength with high ductility
- Corrosion resistance
- About one-third of copper is used in electrical applications
- Other uses are plumbing, heating, and air conditioning
General Properties and Characteristics
- Relatively low strength and high ductility
- Can be extensively formed
- Heavier than iron
- Problems can occur when copper is used at higher temperatures
- Poor abrasive wear characteristics
Characteristics of Copper
- Low temperature properties are better than most other materials
- Strength increases with decreasing temperature
- Material does not embrittle
- Retains ductility under cryogenic conditions
- Conductivity increases with a drop in temperature
- Nonmagnetic
- Nonpyrophoric
- Nonbiofouling
- Wide spectrum of colors
Commercially Pure Copper
- Electrolytic tough-pitch (ETP) copper is refined copper containing between 0.02 and 0.05% oxygen
- Used as a base for copper alloys
- Used for electrical applications such as wire and cable
- Oxygen-free high conductivity (OFHC) copper provides superconductivity
Copper-Based Alloys
- Copper is the base metal
- Imparts ductility, corrosion resistance, and electrical and thermal conductivity
- Standardized by the Copper Development Association (CDA)
- Common alloying elements
- Zinc
- Tin
- Nickel
Copper-Zinc Alloys
- Zinc is the most common alloy addition
- Known as brass
- Alpha brasses
- Ductile and formable
- Strength and ductility increase with increasing zinc content
- Two-phase brasses
- High electrical and thermal conductivity
- Useful engineering strength
- Wide range of colors
- Rubber can be vulcanized to it
- Brasses have good corrosion resistance
- Brasses with 20 to 36% zinc may experience dezincification when exposed to acidic or salt solutions
- Brasses with more than 15% zinc may experience season-cracking or stress corrosion
- Cold-worked brass is usually stress-relieved to remove residual stresses
- Lead can be added to increase machinability
Copper-Tin Alloys
- Tin is more cost effective than zinc
- Alloys with tin are known as bronzes
- Bronzes can technically be any copper alloy where the major alloy addition is not zinc or nickel
- Bronzes have desirable mechanical properties
- Good strength
- Good toughness
- Good wear resistance
- Good corrosion resistance
- Often used for bearings, gears and fittings with high compressive loads
Copper-Nickel Alloys
- Copper and nickel exhibit complete solubility
- High thermal conductivity
- High temperature strength
- Corrosion resistance to a range of materials
- High resistance to stress-corrosion cracking
- Ideal choice for heat exchangers
Aluminum and Aluminum Alloys
General Properties and Characteristics
- Second to steel in quantity and usage
- Used in transportation, packaging, containers, building construction, etc.
- Workable, light weight, corrosion resistance, thermal and electrical conductivity, optical reflectivity, easily finished
- Aluminum is about 1/3 the weight of steel for an equivalent volume
- Four to five times more expensive than steel per pound
- Easily recycled with no loss in quality
- About a 50% recycling rate in the United States
- Biggest weakness of steel is it low modulus of elasticity
Commercially Pure Aluminum
- Soft, ductile, and low strength
- In the annealed condition, pure aluminum has about 1/5th the strength of hot rolled steel
Aluminums for Mechanical Applications
- On a strength to weight basis, aluminum alloys are superior to steel
- Wear, creep, and fatigue resistance are lower
- For the most part, not suitable for high temperature applications
- Performs well in low temperature applications
- Stronger at subzero temperatures than at room temperature
Aluminum vs. Steel
- A selection between aluminum and steel depends on different variables
- Cost
- Weight
- Corrosion resistance
- Maintenance expense
- Thermal or electrical conductivity
- For the automotive industry, aluminum has become increasingly used because of its lower strength to weight ratio and therefore improves fuel efficiency
- Use of aluminum in vehicles has doubled in cars and tripled in SUVs
- Corrosion Resistance of Aluminum and its Alloys
- Pure aluminum is reactive and is easily oxidized
- Oxide provides corrosion resistance layer
- Aluminum oxides are not as reactive as pure aluminum and therefore are not as corrosion resistant
- Oxide coating may cause difficult when welding
- Welding may be done in a vacuum or in inert gas atmospheres
Classification System
- Wrought alloys are shaped as solids
- First digit indicates the major alloy element
- Second digit indicate a modification or improvement
- Last two digits indicate the alloy family
- Temper designations
- F: fabricated
- H: strain hardened
- O: annealed
- T: thermally treated
- W: solution-heat-treated only
Wrought Alloys
|
Major Alloying Element
|
|
|
Aluminum, 99.00%
|
1xxx
|
|
Copper
|
2xxx
|
|
Manganese
|
3xxx
|
|
Silicon
|
4xxx
|
|
Magnesium
|
5xxx
|
|
Magnesium and sulfate
|
6xxx
|
|
Zinc
|
7xxx
|
|
Other
|
8xxx
|
Only moderate temperatures are required to lower strength, so wrought alloys may be easily extruded, forged, drawn, and formed with sheet metal operations
Aluminum Casting Alloys
- Pure aluminum is rarely cast
- High shrinkage and susceptibility to hot cracking
Classification system
|
Major Alloying Element
|
|
|
Aluminum, 99.00%
|
1xx.x
|
|
Copper
|
2xx.x
|
|
Silicon with Cu and/or Mg
|
3xx.x
|
|
Silicon
|
4xx.x
|
|
Magnesium
|
5xx.x
|
|
Zinc
|
7xx.x
|
|
Tin
|
8xx.x
|
|
Other elements
|
9xx.x
|
- First digit indicates the alloy group
- Second and third digit indicates the particular alloy
- Last digit indicates the product form
Other Forms of Aluminum
- Aluminum-Lithium Alloys
- Lithium is the lightest of all metallic elements
- Light weight without compromising strength and stiffness
- Fracture toughness, ductility, and stress corrosion are lower
- Lithium is the lightest of all metallic elements
- Aluminum Foams
- Made by mixing ceramic particles with molten aluminum and blowing gas into the mixture
- Resembles metallic Styrofoam
- Fuel cells of race cars may use aluminum foams
- Provide excellent thermal insulation, vibration damping, and sound absorption
- Made by mixing ceramic particles with molten aluminum and blowing gas into the mixture
Magnesium and Magnesium Alloys
General Properties and Characteristics
- Lightest of commercially important materials
- Poor wear, creep, and fatigue properties
- Highest thermal expansion of all engineering metals
- Strength drops with increase in temperature
- Low modulus of elasticity requires thick parts
- High strength to weight ratio
- High energy absorptions and good damping
- Used in applications where light weight components are the primary concern
Magnesium Alloys and Their Fabrication
- Classification system is specified by ASTM
- Two prefix letters designate the two largest alloying metals
- Numbers following the two letters indicate the percentages of the two main alloy elements
- Magnesium alloys are often processed with sand, permanent mold, die, semisolid, and investment casting
- Wall thickness and draft angle are lower than for aluminum
- Improved machinability
Zinc-Based Alloys
- Over 50% of all metallic zinc is used for galvanizing
- Steel or iron may be hot dipped or be coated using electrolytic plating
- Provides excellent corrosion resistance
- Also used as the base metal in many die casting alloys
- Reasonably high strength and impact resistance
- Can be cast close to dimensional tolerances with extremely thin section
- Low energy costs due to low melting temperature
See Galvinfo.com
Titanium and Titanium Alloys
- Titanium is a strong, lightweight, corrosion resistant metal
- Properties are between those of steel and aluminum
- Less dense than steel
- Can be used in high temperature applications
- High energy costs for fabrication
- Fabrication methods: casting, forging, rolling, extrusion, welding
- Abundant material, but is difficult to process from ore
- Aerospace applications, medical implants, bicycles, heat exchangers are common uses
Nickel Based Alloys
- Outstanding strength and corrosion resistance at high temperatures
- Wrought alloys are known as Monel, Hastelloy, Inconel, Incoloy, and others
- Good formability, creep resistance, strength and ductility at low temperatures
- Can be used in food-processing industries, turbine blades
- Electrical resistors and heating elements typically use nickel-chromium alloys (Nichrome)
- Superalloys are those alloys that are suitable for high temperature applications
Superalloys and Refractory Metals
- Alloys based on nickel, iron, cobalt
- Retain most of their strength even after long exposures to high temperatures
- Strength comes from solid solution strengthening, precipitation hardening, and dispersion strengthening
- The density of superalloys is much greater than that of iron
- Difficult to machine
- Electrodischarge, electrochemical, ultrasonic machining, powder metallurgy
High Temperature Alloys
- Refractory metals
- Use niobium, molybdenum, tantalum, rhenium, and tungsten
- Coating technology is difficult because of their ceramic coating
- Intermetallic Compounds
- Provide properties between metals and ceramics
- Hard, stiff, creep resistant, oxidation resistant, high-temperature strength
- Poor ductility, poor fracture toughness, and poor fatigue resistance
- Difficult to fabricate
Lead, Tin, and Their Alloys
Lead alloys
- High density, high strength and stiffness
- Storage batteries, radiation absorption
- Good corrosion resistance, low melting point, ease of casting or forming
Metallic Glasses
- Amorphous metals are formed by cooling liquid metal extremely quickly so that no crystalline structure can form
- Lacks grain boundaries and dislocations
- High strength, large elastic strain, good toughness, wear resistance, magnetic, corrosion resistance
- Used in load bearing structures, electronic casings, sporting goods
Graphite
- Properties of metals and nonmetals
- Good thermal and electrical conductivity
- Can withstand high temperatures
- Lubricant
- Used as electrodes in arc furnaces
- Rocket-nozzles
- Permanent molds for casting
Summary
- Nonferrous metals are used in a variety of applications
- Many nonferrous metals are lower in weight than steel and are used in applications where weight is a consideration
- Many have better corrosion resistance than steels
- Nonferrous metals are often more expensive than iron based metals or alloys
