What is second phase particle strengthening?

The primary species of precipitation strengthening are second phase particles. These particles impede the movement of dislocations throughout the lattice. Smaller precipitate particles in a host lattice leads to a tensile stress, whereas larger precipitate particles leads to a compressive stress.

What is a second phase particle?

Second-phase particles are another important type of microstructure which can significantly increase strength. The controlled formation of cluster zones and precipitates is discussed in detail, using the Al–Cu and other systems as illustrations.

What are the three basic methods by which metals can be strengthened?

Strengthening mechanisms in metals

• Work hardening.
• Solid solution strengthening and alloying.
• Precipitation hardening.
• Dispersion strengthening.
• Grain boundary strengthening.
• Transformation hardening.
• Polymer.
• Glass.

What are the two strengthening mechanisms in a super alloy?

The Nb-based super alloy can be strengthening by two approaches. One is solid solution strengthening,i.e.W and Mo in the Nb based alloy act as alloy elements to form solid solution, improving high temperature creep properties.

Why are second phase particles important to polycrystalline materials?

Second-phase particles contribute to strengthening, as for conventional polycrystalline materials, where the particles are much finer than the grain size and distributed both within grains and at grain boundaries.

How big are second phase particles in copper?

Figure 11.5 shows an analysis of strengthening in copper alloys containing second-phase particles, 84 where strength is related, via equation 11.13, through the Orowan mechanism. A good description of the particle strengthening, i.e.σ OR proportional to {1/ (λ– ϕ ).l n ( ϕ /2 b )}, is seen down to particle sizes of about 7 nm.

How are second phase particles related to ductility?

While most attention is given to strengthening by second-phase additions, and large second-phase particles seem generally associated with poorer ductility, there is some evidence that correctly sized and distributed second-phase particles might improve ductility.

How big do phase particles have to be?

For significant strengthening the particles must be relatively large, say 3–10 nm, and the simple discussion below considers that they are big enough not to be cut by dislocations, such that the Orowan mechanism operates.