What is the role and mechanism of LPSO phase in mechanical and corrosion behavior of Mg alloy?
It could be demonstrated that conventional thermo-mechanical treatments such as extrusion or rolling cause a significant enhancement in strength of Mg-RE-TM (RE rare earth element, TM = transition metal) alloys containing an LPSO phase without impairing the ductility. This was attributed to the incompatibility of the deformation modes of the LPSO phase and the Mg matrix which causes a substantial strain filed at the LPSO/Mg phase interface facilitating dynamical recrystallization in this regions. Small recrystallized grains firstly improve the strength of the alloy governed by the Hall-Petch relation. Secondly, they have an almost randomized crystallographic orientation which is supposed to help to improve the ductility by softening the strong plastic anisotropy of the Mg matrix imposed by the hcp crystal structure. The LPSO phase itself is aligned along the extrusion or rolling direction after a sufficient extrusion or rolling process which results in a short-fiber strengthening mechanism in analogy to composite materials.
For a detailed description I can recommend you the attached papers.
Article Effect of multimodal microstructure evolution on mechanical ...
Article Effect of long-period stacking ordered phase on mechanical p...
LPSO phase effect on mechanical properties in various mechanisms. one of important reason is formation of kink bands. kinking make the interface of LPSO/Mg be coherent during deformation. in addition to that activation of pyramidal system make increase in elongation and avoiding of formation basal texture. LDRX mechanism is other reason that is explained in my paper. and arresting of twinning growth is another one reason make these alloys be harder than other Mg series.
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