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Callister - An introduction - 8th edition

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228 • Chapter 7 / Dislocations and Strengthening Mechanisms<br />

Equation Summary<br />

Equation<br />

Page<br />

Number Equation Solving for Number<br />

7.2 t R s cos f cos l Resolved shear stress 205<br />

7.4 t crss s y 1cos f cos l2 max Critical resolved shear stress 205<br />

7.7<br />

s y s 0 k y d 1/2<br />

Yield strength (as a function of average grain size)—<br />

Hall–Petch equation<br />

213<br />

7.8 %CW a A 0 A d<br />

b 100 Percent cold work 215<br />

A 0<br />

7.9 d n d n 0 Kt<br />

Average grain size (during grain growth) 224<br />

List of Symbols<br />

Symbol<br />

A 0<br />

A d<br />

d<br />

d 0<br />

K, k y Material constants<br />

t<br />

n<br />

<br />

f<br />

s 0<br />

y<br />

Meaning<br />

Specimen cross-sectional area prior to deformation<br />

Specimen cross-sectional area after deformation<br />

Average grain size; average grain size during grain growth<br />

Average grain size prior to grain growth<br />

Time over which grain growth occurred<br />

Grain size exponent—for some materials has a value of approximately<br />

2<br />

<strong>An</strong>gle between the tensile axis and the slip direction for a single<br />

crystal stressed in tension (Figure 7.7)<br />

<strong>An</strong>gle between the tensile axis and the normal to the slip plane for<br />

a single crystal stressed in tension (Figure 7.7)<br />

Material constant<br />

Yield strength<br />

Processing/Structure/Properties/<br />

Performance Summary<br />

<strong>An</strong> understanding of the strengthening mechanisms for metals necessarily requires<br />

some knowledge concerning (1) the correlation of dislocation motion with plastic<br />

deformation, (2) the characteristics of these defects (i.e., surrounding strain fields<br />

and strain-field interactions), and (3) crystallographic aspects (i.e., the concept of<br />

slip systems). The high hardness (and lack of ductility) of one phase found in steel<br />

(martensite, Section 10.7) is explained by a solid-solution strengthening effect, and,<br />

in addition, to the presence of few slip systems. The following diagram represents<br />

these relationships.

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