Effect of temperature on the transition in deformation modes in Mg single crystals. (1st October 2019)

• Record Type: Journal Article
• Authors: Sim, Gi-Dong; Xie, Kelvin Y.; Hemker, Kevin J.; El-Awady, Jaafar A.
• Is Part Of: Acta materialia. Volume 178(2019)
• Page Start: 241
• Page End: 248
• Publication Date: 2019-10-01
• Subjects: Magnesium -- In-situ SEM -- High-temperature mechanical testing -- Deformation twinning -- Prismatic slip; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2019.08.014
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Here, an experimental study utilizing in-situ scanning electron microscopy (SEM) micro-compression testing and post-mortem transmission electron microscopy (TEM) imaging is presented to quantify the effect of temperature on the transition in deformation modes in twin-oriented Mg single crystals. Single crystal micropillars were fabricated using FIB milling, then tested by in-situ SEM micro-compression from 20 °C to 225 °C. It is observed that plasticity in the deformed Mg microcrystals at temperatures at and below 100 °C is governed by { 10 1 ¯ 2 } extension twinning. However, an anomalous increase of the flow stresses is observed at 100 °C, which is likely due to paucity of dislocation sources that are required to promote twin boundary migration. At 150 °C and above, extension twinning is suppressed and a continuous plastic flow and strain softening induced by prismatic dislocation mediated plasticity is observed. By comparing the current results with those from bulk scale studies for other hexagonal-closed-pack single crystals (e.g. titanium (Ti) and zirconium (Zr)), a general trend for the effect of temperature on the transition in deformation modes in HCP materials is proposed. Graphical abstract: Image 1