Theories of dispersion-phase-strengthening are briefly discussed and then critically examined in the light of experimental evidence obtained with nickel containing a fine dispersion of thoria. The results are in close agreement with Orowan's theory. The work-hardening theory of Fisher, Hart, and Pry, though in qualitative agreement with the experimental results, postulates the formation of concentric dislocation loops around particles of the dispersed phase. Transmission electron micrographs of the nickel-thoria indicate that the formation of prismatic loops near to particles is a more likely process, and this is borne out by analysis of the experimental results.
OrowanE., “Symposium on Internal Stresses in Metals and Alloys”, p. 451 (discussion). 1948: London (Inst. Metals).
4.
AnsellG. S. and LenelF. V., Acta Met., 1960, 8, 612.
5.
TysonW. R., ibid., 1963, 11, 61.
6.
KellyA. and NicholsonR. B., Progress Materials Sc., 1963, 10, 149.
7.
FisherJ. C., HartE. W., and PryR. H., Acta Met., 1953, 1, 336.
8.
LeslieW. C., MichalakJ. T., and AulF. W., “Iron and Its Dilute Solid Solutions” (edited bySpencerC. W. and WernerF. E.), p. 119. 1963: New York and London (Interscience Publishers).
9.
Dew-HughesD. and RobertsonW. D., Acta Met., 1960, 8, 147.
10.
AshallD. W. and EvansP. E., Powder Met., 1967, 10, 326.
