Strengthening solid solution hardening

The nickel base alloys are produced from a group of alloys which have chemical compositions generally over 50 % nickel and less than 10 % iron. They are mainly strengthened by intermetallic precipitation in an austenitic matrix. The cobalt base alloys have a high Co content (40 to 70 %X high Cr (over 20 %), high W (7 to 15 %) and they are strengthened by a combination of carbides and solid solution hardeners. 

The superalloys are strengthened by addition of both solid-solution hardening and precipitate-forming elements. The Fe-Ni-base alloys can be strengthened the least and the Ni-base alloys the most (Fig. 5-8). The... 

Another type of point defect is the incorporation of an impurity atom. Impurity atoms may replace host atoms in the regular crystal structure, in which case they are called substitutional defects, or they may occupy an interstitial site as interstitial impurities. Impurities are often purposely introduced in a lattice to strengthen it (solid solution hardening) or to otherwise alter its properties, e.g., doping a semiconductor to tailor the number and sign of charge carriers. However, as seen later, it is virtually impossible to completely eliminate unwanted impurity atoms. 

Alloying the metals with other components offers other strengthening mechanisms. Adding a second metal as substitutional atoms in the lattice is known as solid solution hardening. The size difference between the solvent (host) atoms and the solute (impurity) atoms strains the lattice and makes it difficult for dislocations to move. Adding smaller atoms that can go into the interstices produces a similar hardening in the lattice. This is the role that carbon plays in the strengthening of steel. 

Strong materials either have a high intrinsic strength, /, (like diamond), or they rely on the superposition of. solid solution strengthening obstacles fo and work-hardening f i, (like high-tensile steels). But before we can use this information, one problem... 

Solution hardening is not confined to 5000 series aluminium alloys. The other alloy series all have elements dissolved in solid solution and they are all solution strengthened to some degree. But most aluminium alloys owe their strength to fine precipitates of intermetallic compounds, and solution strengthening is not dominant... 

Protective scale formers Solid solution strengtheners Age hardening strengtheners Carbide strengtheners Improved scale adhesion (spallation resistance)... 

Other strengthening mechanisms include solid solution formation and strain hardening. Solid solution strengthening involves replacing a small number of atoms in the lattice with substitutional impurities of a slightly different size. This creates strain in the crystal. 

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