Strain rate sensitivity and the portevin-le chatelier effect in Au–Cu alloys

Abstract

The effect of strain rate changes on the flow stress of Au–Cu alloys in the region of strain prior to the start of serrated yielding has been investigated. The measurements of Δσ/Δ Δσ/Δ were found to depend on strain, strain rate, temperature, and composition. Negative values of Δσ/Δ ln ϵ were observed prior to the onset of serrated yielding. The effect of base strain rate on the strain rate sensitivity of the flow stress was correlated with the effect of ϵ on the strain at the onset of serrated yielding. The results are interpreted in terms of a recent model for dynamic strain ageing based on the diffusion of solute atoms to temporarily arrested dislocations. The occurrence of pronounced flow stress transients accompanying strain rate changes was also investigated.

Dynamic Strain Aging in New Generation Cr-Mo-V Steel for Reactor Pressure Vessel Applications

“…This was experimentally confirmed in a number of interstitial [85] and substitutional alloys. [86] Thus, the present results are consistent with the earlier experimental works. In the present work, the kinetic parameters, namely, the strain exponent and the activation energy, were determined from strain rate and temperature dependence of e 0 .…”

“…It is seen from the figure that there is a linear relationship between them. This confirms that the strain aging model proposed by McCormick and Van Den Beukel [81,86] to be the appropriate mechanism for the occurrence of DSA in the present study. The solutes most likely to migrate to the waiting dislocations were identified from the activation energy calculations as carbon or nitrogen (i.e., C/N).…”

“…The expression for dr/dln_ e, derived by Van Den Beukel, [86] decreases with strain due to increasing contribution as a result of DSA. This was experimentally confirmed in a number of interstitial [85] and substitutional alloys.…”

“…The value of b determined in this work is similar to that found in other interstitial alloys such as Fe-C and Ni-C. [87,88] The basis for Eq. [4] is the expression for the change in flow stress accompanying the change in strain rate, which was derived by Van Den Beukel [86] and is given subsequently:…”

“…It was shown that the strain rate sensitivity defined as dr/dln_ e is a function of temperature, strain, and strain rate change ratio, [85,86] based on the model of DSA entailing enrichment of solute concentration at the dislocation during its waiting period at obstacles. The expression for dr/dln_ e, derived by Van Den Beukel, [86] decreases with strain due to increasing contribution as a result of DSA.…”