Strain rate dependence of compressive behavior in an Al-Zn-Mg alloy processed by ECAP

Afifi, Mohamed A., Wang, Ying Chun, Cheng, Xingwang, Li, Shukui and Langdon, Terence G. (2019) Strain rate dependence of compressive behavior in an Al-Zn-Mg alloy processed by ECAP. Journal of Alloys and Compounds, 791, 1079-1087. (doi:10.1016/j.jallcom.2019.03.390).

Abstract

Experiments were conducted to study the compressive mechanical properties of an Al-Zn-Mg alloy after solid solution treatment and equal-channel angular pressing (SS-ECAP) using strain rates ranging from 1.0 × 10 ⁻³ to 3.0 × 10 ³ s ⁻¹ . The results show that SS-ECAP processing enhances the compressive strength due to the high dislocation density, large numbers of fine precipitates and grain refinement. The alloy in both the peak-aged (as-received) and the SS-ECAP states shows a strain rate strengthening effect such that the strain rate sensitivity increases with increasing strain rate. The high volume fraction of fine precipitates in the SS-ECAP alloy decreases the strain rate sensitivity. The coarse precipitates in the peak-aged alloy are fragmented while their sizes increase in the SS-ECAP alloy due to dynamic precipitation assisted by the high density of dislocations during compressive testing. With increasing strain rate, the size of the precipitates further increases for the SS-ECAP alloy and this is influenced by accelerated dislocation motion. During compression, the T (Al ₂₀ Cu ₂ Mn ₃ ) and E (Al ₁₈ Mg ₃ Cr ₂ ) phases evolve into a new tetragonal phase containing Mg, Mn, Cr and Zn with Al.

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Contributors

Author: Terence G. Langdon

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