Deformation and spallation of a magnesium alloy under high strain rate loading

Abstract

We investigate deformation and damage of a magnesium alloy, AZ91, under high strain rate (∼10 5 s −1 ) loading via planar impact. The soft-recovered specimens are examined with electron back-scatter diffraction (EBSD). EBS-D analysis reveals three types of twinning: {1012} extension, {1011} contraction, and {1011}-{1012} double twinning, and their number density increases with increasing impact velocity. The extension twins dominate contraction and double twins in size and number. Dislocation densities of the recovered specimens are evaluated with x-ray diffraction, and increase with increasing impact velocity. X-ray tomography is used to resolve three-dimensional microstructure of shock-recovered samples. The EBSD and tomography re- * sults demonstrate that the second phase, Mg 17 Al 12 , plays an important role in both deformation twinning and tensile cracking. Deformation twinning appears to be a common mechanism in deformation of magnesium alloys at low, medium and high strain rates, in addition to dislocation motion.

Dynamic in-situ imaging of methane hydrate formation and self-preservation in porous media

“…Recent instrument developments (Mokso et al, 2017) allow to capture processes with sub-second temporal resolution. Important applications of fast imaging include multi-phase fluid flow in porous rocks (Youssef et al, 2013;Blunt et al, 2013;Fusseis et al, 2014a), deformation and geomechanical testing of samples (Baker et al, 2012;Li et al, 2015;Wang et al, 2016), and hydraulic fracturing (Kiss et al, 2015).…”

Effect of low temperature and high strain rate compression on the microstructure evolution and mechanical behavior of Mg-2Y-0.6Nd-0.6Zr alloy

“…The compression true stress-strain curve shows concave or "s" like curve in the early deformation stage, which is related to the emergence of {10 1 false¯2} tension twins. 28, 29 Generally, there is an elastic-plastic transition zone at the initial deformation stage in the flow curve, which is mainly controlled by slip and {10 1 false¯2} twins. After this region, the material reaches the yield point, followed by a relatively long work hardening region, which is attributed to the formation of twins (especially {10 1 false¯2} tensile twins).…”

A unified method for studying impact particle relation and spallation under shock loading

“…At present, the main research methods include: (1) The spallation behavior of the material was analyzed by measuring the particle velocity history and the internal stress history of the material [8][9][10]; (2) The damage mechanism and damage evolution behavior of the materials were obtained by statistical analysis of the recovered impacted samples [11]. (3) The spall process is recorded and analyzed by X ray flash radiography and high speed photography [12,13].…”