Revealing deformation mechanism of fine-grained Mg alloys via neutron diffraction analysis

Somekawa, Hidetoshi*; Gong, W.   ; Kawasaki, Takuro   ; Harjo, S.   ; Singh, A.*; Tomota, Yo*

Deformation mechanism at room-temperature of fine-grained Pure Mg, AZ31 and Mg-Mn alloys is examined through in-situ neutron diffraction method and postmortem microstructural observations. Extension twins do not form in any of the specimens. In the AZ31 alloy, lattice strain and integrated intensity of individual planes change differently with progression of tensile tests, indicating large plastic anisotropy. This is due to large number of dislocation slips on not only basal but also prismatic planes. Whereas, Pure Mg and Mg-Mn alloy show a small difference in lattice strain and integrated intensity between diffraction peaks, because grain boundary sliding plays a role in relaxation of stress accumulations at grain boundaries, with less dependence on crystallographic orientation. Neutron diffraction analysis in Pure Mg and Mg-Mn alloy reveals that dislocation slips (on mainly basal plane) are generated by mechanisms associated with both accommodation process for grain boundary sliding and general intragranular plastic deformation.