An Investigation of Detwinning Behavior of In-plane Compressed E-form Mg Alloy During the In Situ Tensile Test

Magnesium alloys and applications

Abstract: The methods for producing magnesium are briefly described and its alloying behaviour is discussed with particular reference to the roles of individual alloying elements. Cast and wrought alloys are considered separately and particular attention is paid to microstructure–property relationships and corrosion behaviour. Alloys produced via new processing techniques are treated separately and mention is made of metal matrix composites and the use of rapid solidification to produce amorphous and other novel materials. Finally, current and future trends in the use of magnesium alloys are considered together with examples of recent applications.MST/2023

Deformation twinning in AZ31: Influence on strain hardening and texture evolution

Abstract: This paper describes the main results from an experimental investigation into the consequences of deformation twinning in AZ31 on various aspects of plastic deformation, including the anisotropic strain-hardening rates, the tension/compression yield asymmetry, and the evolution of crystallographic texture. It was seen that AZ31 exhibited unusually high normalized strain-hardening rates compared to α-Ti that occurred beyond the strain levels where extension twins have completely altered the underlying texture. This observation challenges the validity of the generally accepted notion in the current literature that the high strain-hardening rates in AZ31 are directly caused by extension twins. It is postulated here that the thin contraction twins are very effective in strain hardening of the alloy by restricting the slip length associated with pyramidal 〈c + a〉 slip. This new hypothesis is able to explain the major experimental observations made in this study and in the prior literature. We have also presented a new hypothesis for the physical origin of the observed differences in the thicknesses of the extension and contraction twins. The stress fields in selected matrix–twin configurations were modeled using crystal plasticity finite element models. The contraction twin ( 0 1 ¯ 1 1 ) [ 0 1 ¯ 1 2 ¯ ] was predicted to form an internal extension twin ( 0 1 1 ¯ 2 ) [ 0 1 ¯ 1 1 ] , resulting in the commonly observed “double twin” sequence. The extension twin is suggested to inhibit thickening of this double twin by loss of twin–matrix coherency. Extension twins were predicted to retain their coherency and thus thicken.

Influence of {10-12} extension twinning on the flow behavior of AZ31 Mg alloy

Abstract: Uniaxial compression tests were performed on samples cut along the extrusion direction from AZ31 Mg alloy tubes. A stage of increasing work hardening rate was observed on representative true sigma-epsilon curves. Specimens compressed to various strain levels were examined by optical microscopy and electron backscattered diffraction (EBSD) techniques. The results indicate that the widespread formation of intersecting {10-12} extension twins is responsible for the increased strain hardening rate. (c) 2006 Elsevier B.V. All rights reserved.

Strengthening and toughening of magnesium alloy by {1 0 −1 2} extension twins

Abstract: The mechanisms of strengthening and toughening of hot-rolled AZ31 magnesium alloy by {1 0 −1 2} extension twins during strain path changed recompression are studied in the current paper. Under the favorable orientation, {1 0 −1 2} extension twinning can occur in {1 0 −1 2} twins generated by precompression along the rolling direction. Grain refinement by extension twins dramatically enhances both yield stress and peak stress of reloading along the transverse direction without any degradation in elongation, while the effect is closely related with the level of prestrain.

Microstructure and mechanical properties of Mg–Al based alloy with calcium and rare earth additions

Abstract: Effects of calcium and rare earth additions to alloy AZ91 on the microstructure and mechanical properties were investigated. The results indicated that small amounts of calcium addition to AZ91 did not cause the formation of any new phases in the microstructure, but refined the as-cast microstructure and increased the thermal stability of the β phase so that the yield strength and creep resistance of the alloy were significantly improved. Additions of lanthanum-rich misch metal (MM) resulted in the formation of needle-shaped particles, which showed very high thermal stability and did not dissolve into the matrix after the solution treatment at 420 °C for 20 h. The strength as well as creep resistance of the alloy at elevated temperatures was remarkably increased when MM was added combined with calcium. The highest creep resistance was obtained from the alloy with 3% of MM and 0.3% of calcium addition and its steady state creep rate reached as low as 2.69×10 −8 s −1 , one order of magnitude lower than that of alloy AZ91 without MM and calcium additions.