What are the differences between the electrical and thermal conductivity of metallic materials?

Table of Content [Hide]

In the performance evaluation of metallic materials, electrical conductivity and thermal conductivity are frequently mentioned. Both are important indicators of a metal's ability to transfer energy, but they differ in concept, application, and influencing factors.

Many people mistakenly believe that good electrical conductivity always equates to good thermal conductivity; in fact, while they are related, they are also distinctly different.

Basic Concepts of Electrical Conductivity and Thermal Conductivity

1. Electrical Conductivity

Electrical conductivity describes a metal's ability to allow electric current to pass through it.

Essentially, it is free electrons in a metal move under the influence of an electric field, forming an electric current.The more free electrons and the smoother their movement, the better the conductivity.

High conductivity means low resistance and low energy loss during transmission.

Typical highly conductive metals: Copper (Cu), Silver (Ag), Aluminum (Al)

2. Thermal Conductivity

Thermal conductivity describes a metal's ability to conduct heat.

Heat is energy, and metals dissipate heat primarily through two mechanisms: the thermal motion of free electrons (primarily) and the propagation of heat through lattice vibrations (phonons).

High thermal conductivity means that heat energy moves quickly and dissipates heat more easily and evenly.

Typical metals with high thermal conductivity: copper, silver, aluminum, gold, and magnesium alloys.

Differences between Electrical Conductivity and Thermal Conductivity

Main factors affecting electrical conductivity:

Impurities (the purer the material, the better the conductivity)
Temperature (higher temperature, lower conductivity)
Crystal defects and deformation
Element type (silver is the highest, copper is the next best)

Main factors affecting thermal conductivity:

Number of free electrons
Crystal lattice structure
Alloy composition
Temperature (generally, thermal conductivity decreases slightly with increasing temperature)

How to Choose in Practical Engineering?

1. If electrical conductivity is required

Copper, copper alloys (e.g., C1100, C2680)
Aluminum alloys (e.g., 6061, 5052)

Applications: Electrical boxes, power supply housings, busbars, grounding terminals.

2. If thermal conductivity is required

Copper, aluminum, magnesium alloys
High-purity metals are better than alloys.

Applications: Heat sinks, flat heat plates, LED bases.

3. Both heat dissipation and sufficient strength are required

Common choices: Aluminum alloys 6061, 5052 (most commonly used in the sheet metal industry)

Reasons: Good thermal conductivity, Lightweight, Suitable strength and good machinability.

4. Strength requirements are higher than thermal conductivity

Stainless steel is a common choice, although poor thermal conductivity, it has a strong structure and is corrosion resistant.

Conclusion

While both electrical and thermal conductivity of metals are related to free electrons, their applications are entirely different:

Electrical conductivity determines whether a metal is suitable as a medium for transmitting electrical energy.
Thermal conductivity determines whether a metal is suitable as a heat dissipation material.

In practical material selection, engineers typically need to consider Structural strength, Processing technology (especially sheet metal bending and welding), Cost and Appearance requirements. A comprehensive evaluation of which performance is more important before deciding which metal to use.