In situ analysis of the influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy

Abstract

The influence of twinning on the strain hardening rate and fracture mechanism in AZ31B magnesium alloy was studied in this work by in situ microstructural analysis during tensile testing in a chamber of scanning electron microscope. Three types of samples used in this study were obtained by (1) extrusion (as-supplied), (2) I-ECAP and (3) I-ECAP followed by side upsetting. Microstructures, textures and mechanical properties were examined after each processing step. An analytical equation was used to describe flow stress curves of the samples which exhibited various modes of deformation (1) only by slip, (2) dominated by tensile twinning followed by slip and (3) dominated by contraction twinning followed by slip. It was shown that tensile twinning increases strain hardening rate, while the opposite is observed for contraction twinning. The effective Schmid factors for slip in volumes deformed by tensile and contraction twinning were determined in this work using modelling approach as 0.215 and 0.45, respectively. Contraction twinning was also revealed to be responsible for an earlier fracture of the extruded sample subjected to tension, since microcracking was shown explicitly to be initiated within twins.

The role of microstructure and texture in controlling mechanical properties of AZ31B magnesium alloy processed by I-ECAP

“…Despite I-ECAPed texture indicating importance of this kind of deformation, it was shown that microstructure of the annealed sample was severely twinned at true strain 0.15. It is especially interesting as twinning is usually expected to decrease ductility [31][32][33] while in this work it was revealed in the sample, which exhibited extraordinary elongation along tensile direction. EBSD analysis of the deformed structure (Fig.…”

Crack formation of steel reinforced concrete structure under stress in construction period

“…In this study, we discussed over the reasonability of definite element analysis of steel reinforced concrete structure [23]. It can be known from the actual measurement of deformation that, deformation rate of steel reinforced concrete (C60, C50) column in low floor became higher than the simulated value in the late period; and the vertical deformation of steel reinforced concrete (C50, C60) column was smaller than that of steel reinforced concrete (C40) column [24]. During construction, deformation of structural component and accumulation of stress are different as construction order and procedures of exerting construction load are different.…”

Characterisation of Mg–Li alloy processed by solution treatment and large strain rolling

“…Mg-Li alloy is one of the lightest structural metallic materials, which shows great potential in transportation systems and electric equipments due to the high specific strength and good formability at ambient temperature. 1,2 Furthermore, The addition of Li to magnesium alloy can not only reduce its density but also markedly improve the formability by changing the crystal structure from hexagonal close packed to body centred cubic (BCC) when the amount of Li exceeds 11 wt-%. 3 The b-phase Mg-Li alloy has lower density and better formability than other a-phase or (a þ b)-phase alloys.…”