Fizika Nizkikh Temperatur: Volume 46, Number 10 (October 2020), p. 1232-1241 ( to contents , go back )
Plastic deformation of micrograined magnesium alloy AZ31 at low temperatures
N. V. Isaev and P. A. Zabrodin
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine Kharkiv 61103, Ukraine
Received March 23, 2020, published online August 21, 2020
The features of the plastic deformation of a micrograined magnesium alloy AZ31 under tension in the temperature range 4.2–295 K were studied. The samples were deformed in two structural states: the initial state after eight passes of equal channel angular pressing (eight passes of equal channel angular pressing and annealed (after isothermal annealing at 573 K). In both cases, with decreasing temperature, an increase in the yield strength, strain hardening coefficient, and a decrease in ductility were observed. The dependence of the hardening coefficient of the deformation is nonmonotonic compared to the initial one, which is explained by an increase in twinning activity due to an increase in grain size upon annealing. The low Hall–Petch parameters for the yield strength at room temperature indicate a high activity of the basal slip of the dislocations, due to the mixed texture that forms after 8ECAP and does not radically change upon annealing. The yield strength of the studied polycrystals is determined by the thermofluctuation motion of mainly basal dislocations. The empirical parameters of this motion in the temperature range 4.2–295 K, obtained from the analysis of the temperature dependences of the yield strength and activation volume, correspond to the mechanism of interaction of dislocations with local obstacles formed by impurity atoms and forest dislocations.
Key words: magnesium alloy, equal-channel angular pressing, strain hardening rate, activation volume.