BeginnerTopic 12 of 100Materials & Chemical
Strengthening mechanisms
Grain refinement, solid solution, strain hardening and precipitation hardening.
In depth
Strength increases when dislocation motion is hindered: grain refinement (Hall-Petch σ_y=σ₀+kd^{-1/2}), solid-solution, strain hardening, precipitation/age hardening and dispersion strengthening, and martensite. Each comes with ductility or toughness trade-offs.
Key points
- Smaller grains stronger
- Orowan mechanism
- Combine mechanisms
ExampleAluminium 6061-T6 is age-hardened with Mg₂Si precipitates.
What is Strengthening mechanisms?
Grain refinement, solid solution, strain hardening and precipitation hardening.
Why is it important to understand strengthening mechanisms?
Strengthening mechanisms raise the strength of a metal by hindering dislocation movement, which is how most alloys are made stronger.
What are the main strengthening mechanisms?
Grain refinement, solid solution strengthening, strain hardening and precipitation hardening, each of which blocks dislocations in a different way.
Why do strengthening methods often reduce ductility?
Obstacles that stop dislocations also make it harder for the material to deform plastically, so a trade-off is usual.
How is Strengthening mechanisms used in practice?
Typical applications include choosing a precipitation-hardened aluminium for an aircraft fitting, refining the grain size of a steel to improve yield strength and adding alloying elements to create solid solution strengthening in brass.
What should I learn before Strengthening mechanisms?
Study "Impact testing" first (topic 11 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Strengthening mechanisms?
Smaller grains stronger. Orowan mechanism. Combine mechanisms.
Can you give an example of Strengthening mechanisms?
Aluminium 6061-T6 is age-hardened with Mg₂Si precipitates.
What comes after Strengthening mechanisms?
The next topic is "Strain hardening", which builds directly on this one.
How difficult is Strengthening mechanisms?
It is classed as Beginner in Materials & Chemical (topic 12 of 100). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.