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New observations on the mechanisms of dynamic strain aging and of jerky flow

1979; University of Toronto Press; Volume: 27; Issue: 7 Linguagem: Inglês

10.1016/0001-6160(79)90130-5

1878-0768

R. A. Mulford, U.F. Kocks,

Metallurgy and Material Forming

Abstract The rate sensitivity of the flow stress was investigated as a function of pre-strain for a commercial nickel alloy (INCONEL 600) and for polycrystalline Al-1% Mg. over a wide temperature range encompassing the regime of jerky flow. Anomalies were observed which suggest that the dynamic strain aging mechanism operates over a wider temperature range than that in which jerky flow is found. A detailed analysis shows that a negative rate sensitivity is associated with the strain hardening contribution to the flow stress from the beginning of deformation. The total rate sensitivity becomes negative only after this strain hardening contribution dominates. This suggests an interpretation of the ‘critical strain’ for the appearance of jerky flow, which does not rely on the production of vacancies and moreover casts doubt on any interpretation that associates dynamic strain aging with the interaction of mobile solutes with the moving dislocations. Instead, a dislocation arrest model is used in which solute atoms diffuse along dislocations at forest intersections.