Micromechanical response of pure magnesium at different strain rate and temperature conditions: twin to slip and slip to twin transitions

Temperature Dependent Critical Stress for {10-12} Twinning in Magnesium Micropillars at Cryogenic Temperatures

“…To promote consistency with our recent work [25], where the mechanical response of [2110] Mg microcrystals compressed at different temperature and strain rates was reported, further 99.999% pure single crystal Mg micropillars have been compressed at cryogenic temperature and multiple strain rates along the same crystallographic direction, allowing to provide experimental data in thus far uninvestigated regions of the microscale pure Mg property space. This research activity hence extends the understanding of a predominant deformation mode in Mg and raises particular interest for low-temperature manufacturing methods and low-temperature applications [25].…”

“…From our microscale experiments, because of initial absence of grain boundary and a relatively low density of pre-existing dislocations, it is reasonable assuming that the long-range internal stress field does not change within the values of T and ε a-c). The magnitudes of the stress drops associated to the twin formation are shown in (d) and compared to those measured at higher temperatures from our previous work [25]. The variation of σ y with strain rate is illustrated in (e).…”

“…The tests were performed with the in situ Alemnis microindenter module (Alemnis AG, Switzerland) previously used at elevated temperature [25] but suitably modified for cryogenic conditions, inside a DSM 962 (Zeiss, Germany) scanning electron microscope (SEM). The main components of the system are reported elsewhere [26][27][28].…”

“…The variation of the stress (denoted σ y ) that preceded the first load drop associated to the occurrence of twinning is shown in Fig. 2e and compared to that obtained during [2110] microcompressions at higher temperatures [25] and [0110] microcompressions at room temperature [1]. A substantially higher critical stress for twinning has been detected at cryogenic temperature at 10 -4 s -1 compared to what was measured at room or elevated temperatures even up strain rates of 5 × 10 -2 s -1 , and this cryogenic strength is observed to further increase with strain rate.…”

“…Note that the error bars consider also uncertainties (±100 nm) in the SEM measures of the dimensions of the structures. (References: a [25], b [1]). investigated here.…”