2005 Volume 91 Issue 5 Pages 445-456
Although the discussion on the mechanism determining the strength of metals has a long history, it has not come to a satisfactory conclusion on its many aspects. Recent works on this subject is reviewed on the basis of the dislocation theory. Subjects discussed in this article contain such items as (1) strength due to the Peierls stress, (2) solution hardening, (3) precipitation hardening, (4) work hardening, and (5) strength related to the crystalline grain size. Various unsolved problems on these subjects are pointed out. Concerning the Peierls stress, available atomic calculations are still unsuccessful for explaining the general relationship between the stress and the lattice parameters. On the solution hardening, theories presented so far fail to give a quantitative explanation on the temperature dependence of the yield stress. It is suggested that a satisfactory theory should take into account the interaction between a dislocation and plural solute atoms at a thermal activation event. Regarding the work hardening, the necessity of the further discussion on the saturation stress are stressed. Concerning the grain-size effect, the dependence of coefficients in the Hall-Petch relation on the material species should be clarified more precisely.
