Dislocation Properties in High Purity Molybdenum Single Crystals at Very Low Temperatures

Abstract

High purity molybdenum single crystals were deformed in tension and compression along the symmetric double slip orientation [110] in the temperature range from 300 K down to 0.5 K with strain rates between 10−3 and 10−5 s−1. The activation volume was measured by stress relaxation tests. The dislocation structure of the deformed crystals (T https://www.w3.org/1998/Math/MathML"> ≫ ¯ ¯ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429070914/564d64e2-e041-4c69-948a-24fd34915041/content/eq1077.tif" xmlns:xlink="https://www.w3.org/1999/xlink"/> 1.85 K) was examined by high voltage electron microscopy. It was established that the low temperature increase of the critical shear stress exhibits three distinct temperature regimes with different temperature dependences. These non-uniformities are discussed in terms of recently developed theories of kink-pair formation and kink-kink interactions on screw dislocations in bcc metals. The HVEM observations suggest that the mobility of screw dislocations at very low temperatures should be determined by the combined effects of the PEIERLS barriers and the jog dragging.