Nonferrous Metals
Aluminum, copper alloys, titanium, zinc and magnesium as choices for weight, conductivity, corrosion and manufacturing needs.
Choose the useful property, then check the tradeoff
Choose the useful property, then check the tradeoff
Nonferrous metals have a base other than iron. They are not all lightweight, corrosion-proof or easy to machine. A useful first comparison names both the benefit and the constraint.
| Metal | Why choose it? | Typical use and tradeoff |
|---|---|---|
| Aluminum | Low density, useful corrosion resistance and ready availability in extruded shapes. | Frames and housings. Lower elastic stiffness than steel; alloy and temper strongly affect strength. |
| Copper | High electrical and thermal conductivity. | Conductors and heat-transfer parts. Relatively high density and cost; alloying usually reduces conductivity. |
| Titanium | Useful strength relative to weight and corrosion resistance. | Aerospace and chemical-service parts. Material and processing costs can outweigh the weight saving. |
| Zinc | Useful casting behavior and ability to protect steel as a coating. | Die-cast hardware and galvanized products. Temperature and load requirements limit use. |
| Magnesium | Very low density among structural metals. | Light housings. Corrosion protection and suitable manufacturing procedures matter. |
These are material-selection comparisons. For cutting operations, continue to Milling Operations, Lathe Operations and Feeds and Speeds.
Aluminum needs both an alloy label and a condition
Aluminum needs both an alloy label and a condition
Aluminum is sold in many alloys and conditions. Wrought products are shaped by processes such as rolling or extrusion. Their familiar four-digit labels are organized into series, including 1xxx through 7xxx. A series is a family, not a hardness scale: a higher first digit does not guarantee a harder or better part.
6061 and 7075 are common alloy labels to look for in supplier literature. Compare data for the actual product form and temper rather than treating either number as a complete specification. Cast aluminum uses a different designation system; do not transfer wrought-number rules to cast products.
A suffix such as -O or -T6 identifies a condition as part of an alloy-temper designation. It must stay attached to the alloy on an order. See Heat Treating Metals for why processing history matters.
The Aluminum Extruders Council defines the two tempers:
- -O: “Annealed” — “Thermally treated to obtain the lowest strength temper.”
- -T6: “Solution heat-treated and artificially aged.”
Use the governing product specification for an actual purchase.
Aluminum series 1xxx–7xxx identify purity or the main alloying additions
Aluminum series 1xxx–7xxx identify purity or the main alloying additions
| Series | Principal alloying element or purity |
|---|---|
| 1xxx | Commercially pure aluminum: at least 99% aluminum. |
| 2xxx | Copper. |
| 3xxx | Manganese. |
| 4xxx | Silicon. |
| 5xxx | Magnesium. |
| 6xxx | Magnesium and silicon. |
| 7xxx | Zinc. |
Source for the series table
The Aluminum Association's aluminum-alloy overview identifies these series and their principal additions. It describes 1xxx as “aluminum 99 percent or higher purity.” The series names do not list every element in an individual alloy; for example, the Association also identifies magnesium and possible copper and chromium additions in 7xxx alloys.
6061 favors fabrication; 7075 offers higher strength in the T6 condition
6061 favors fabrication; 7075 offers higher strength in the T6 condition
Compare like conditions: 7075-T6 has higher tensile strength than 6061-T6. The alloy number alone does not establish the strength of the material in hand.
| Alloy | Typical uses | Fabrication considerations |
|---|---|---|
| 6061 | Truck and marine frames; tanks. | Weldable and readily machined. Welding can change the temper in the weld area. |
| 7075 | Aircraft components, molds and industrial tooling. | Good machinability, but generally considered unsuitable for welding because of cracking susceptibility. |
Sources and comparison limits
The Aluminum Association identifies 6061 use in truck and marine frames and 7075 use in aircraft. Metal Supermarkets' 6061/7075 comparison supports the T6 tensile-strength comparison, tank and tooling uses, machinability and welding differences. Its fabrication discussion notes that restoring the weld area's original temper in 6061 may require further heat treatment and aging. Compare the supplier's data for the actual temper and product form.
Brass and bronze trade some of copper's conductivity for other properties; Practice
Brass and bronze trade some of copper's conductivity for other properties
Brass is principally a copper-zinc alloy. Depending on grade, it can offer useful forming or machining behavior for fittings, hardware and decorative parts. Do not assume every brass has the same machinability or suitability for contact with drinking water.
Bronze traditionally means copper-tin alloy, but commercial names also include aluminum bronze and silicon bronze. Bronzes serve in bearings, bushings, gears and corrosion-resistant hardware, depending on grade. The word “bronze” alone is not enough to buy a bearing material.
For a conductor, begin with conductivity requirements. For a bearing, begin with load, speed, lubrication and wear. The same copper-based family will not automatically win both comparisons.