Mechanisms for grain size hardening and softening in Zn

✍ Scribed by H. Conrad; J. Narayan

• Book ID: 108491933
• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 159 KB
• Volume: 50
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(02)00357-9

✦ Synopsis

An analysis of the rate-controlling mechanisms corresponding to effect of grain size d ϭ 10 Ϫ9 to 10 Ϫ3 m on the flow stress of Zn at 300K and e ˙ϭ 10 Ϫ 4 Ϫ 10 Ϫ 3 s Ϫ1 was performed. Three grain size regimes were indicated: Regime I, dϷ10 Ϫ6 -10 Ϫ3 m, Regime II, dϷ10 Ϫ6 -10 Ϫ8 m and Regime III, d Ͻ 10 Ϫ8 m. Grain size hardening occurred in Regimes I and II and grain size softening in Regime III. The intersection of pyramidal forest dislocations by basal dislocations was concluded to be the rate-controlling mechanism in both Regimes I and II, the major effect of the grain size being on the forest and gliding dislocation densities. The absence of twinning and a dislocation cell structure distinguished Regime II from I. The grain size softening observed in Regime III is in better accord with grain boundary shear than with grain boundary diffusion creep.