GTBL042-08 GTBL042-Callister-v3 October 4, 2007 11:51
2nd Revised Pages8.10 Solid-Solution Strengthening • 259Tensile strength (MPa) Tensile strength (ksi)Yield strength (MPa)Elongation (% in 2 in.)4003002001801601401201008060
0 1020 3040 50605040302060504030Yield strength (ksi)20Nickel content (wt%)0 1020 3040 50251510Nickel content (wt%)0 1020 3040 50
Nickel content (wt%)(a) (b)(c)Figure 8.16 Variation with nickel content of (a) tensile
strength, (b) yield strength, and (c) ductility (%EL) for
copper–nickel alloys, showing strengthening.increase the strength of the material. Boundaries between two different phases are
also impediments to movements of dislocations; this is important in the strengthening
of more complex alloys. The sizes and shapes of the constituent phases significantly
affect the mechanical properties of multiphase alloys; these are the topics of discus-
sion in Sections 11.7, 11.8, and 15.1.8.10 SOLID-SOLUTION STRENGTHENING
Another technique to strengthen and harden metals is alloying with impurity atoms
that go into either substitutional or interstitial solid solution. Accordingly, this is
solid-solution calledsolid-solution strengthening.High-purity metals are almost always softer and
strengthening weaker than alloys composed of the same base metal. Increasing the concentration
of the impurity results in an attendant increase in tensile and yield strengths, as
VMSE indicated in Figures 8.16aand 8.16bfor nickel in copper; the dependence of ductilityPure/Larger/
Smaller/
Interstitialon nickel concentration is presented in Figure 8.16c.
Alloys are stronger than pure metals because impurity atoms that go into solid
solution ordinarily impose lattice strains on the surrounding host atoms. Lattice strain
field interactions between dislocations and these impurity atoms result, and, conse-
quently, dislocation movement is restricted. For example, an impurity atom that is