YIELD STRESS OF FINE-GRAINED MATERIALS

A model is proposed for the yield stress of ultra-fine grained materia ls based upon Coble creep. Using Coble creep with a threshold stress f or finer grains and conventional Hall-Fetch strengthening for larger g rains, an analytical relation is derived for the yield stress as a fun ction of grain size for a range from very large to very small. A grain size distribution is incorporated into the analysis to account for a distribution of grain sizes occurring in most specimens. This result i s compared with experimental data from Cu and NiP and shown to be in g ood agreement. Acta Metallurgica Inc. Published by Elsevier Science Lt d.