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Effect of Long‐Term Storage on Microstructure and Microhardness Stability in OFHC Copper Processed by High‐Pressure Torsion
Author(s) -
Almazrouee Abdulla I.,
AlFadhalah Khaled J.,
Alhajeri Saleh N.,
Huang Yi,
Langdon Terence G.
Publication year - 2019
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201801300
Subject(s) - materials science , microstructure , indentation hardness , metallurgy , grain size , recrystallization (geology) , torsion (gastropod) , copper , composite material , medicine , paleontology , surgery , biology
Tests are conducted to evaluate the effect of long‐term storage on the microstructure and microhardness of an oxygen‐free high conductivity (OFHC) copper after processing by high‐pressure torsion (HPT) for various numbers of revolutions at ambient temperature. Results are presented for samples subjected to storage at room temperature through periods of either 1.25 or 7 years. The results show that an increase in storage time leads to a coarsening of the ultrafine‐grained structure produced by HPT processing and a corresponding decrease in the microhardess where this is associated with the occurrence of recrystallization and grain growth. Plots of hardness against equivalent strain reveal a three‐stage behavior with much lower hardness values over a range of equivalent strains of ≈2–8. This behavior is similar after both storage periods but the hardness values are lower and the grain sizes are larger after storage for the longer time. The results demonstrate that long‐term storage has a significantly detrimental effect on the microstructure and hardness of ultrafine‐grained OFHC Cu.