Work Hardening of Magnesium Single Crystals Deformed to Stage B at Room Temperature

Abstract

Magnesium single crystals of purity (99.8 wt%) deformed to stage B on the work-hardening curve at the temperature of 293 K and at a strain rate of 10 −3 s −1 were investigated. The modied Bridgman method was used to obtain the crystals of the preferred orientation of (0001)⟨1120⟩ as primary slip system. By using the method based on the experimental gradient matrix, the activity of slip systems was obtained in magnesium single crystals deformed to shear strain 1.2γ, where well developed stage B of work hardening was observed. It was shown that primary (0001)⟨1120⟩ slip system was dominant in the whole investigated range of the examined deformation. The observation and analysis of etch pits on the {1210} plane showed the heterogeneous distribution of dislocations formed during deformation into walls of dislocations perpendicular to the (0001) slip plane. The suggested model of work hardening of magnesium single crystals, which is worth taking into consideration, shows the inuence of the long-range stress eld derivating from the groups of dislocations arranged in dislocation walls.

Anomalous hardening in magnesium driven by a size-dependent transition in deformation modes

“…The disk was then chemically polished in a solution of 10% nitric acid in deionized (DI) water, followed by electropolishing using a solution of 5% nitric acid in methanol electrolyte, to remove the oxide and EDM induced damage surface layers. The initial dislocation density was measured using the etch-pitting technique by exposing the surface of the sample to a solution consisting of 10 g ammonium chloride dissolved in 50 cm 3 of DI water 69,70 . The estimated initial dislocation density was on the order of 10 9 m -2 .…”

Latent hardening effect under self- and coplanar dislocation interactions in Mg single crystals

“…The measurements of dislocation densities in the primary and forest slip systems in Mg single crystals by TEM [19] and etch-pit [25,27,24] techniques indicate that during the onset of stage A in tension the dislocation density in the basal slip system increases roughly linearly with the flow stress and is at least two orders higher than the density of forest dislocations. From the perspective of dislocation storage, the interactions between basal dislocations of coplanar slip systems should thus be more important than the interactions between basal and non-basal dislocations.…”

“…In Mg single crystals, basal slip is dominant deformation mechanism in a wide range of orientations and over a broad range of temperatures [19][20][21][22][23][24]. The interactions of basal slip with other slip and twinning systems occur frequently during plastic flow and control the work-hardening of Mg.…”