Reversible motion of twin boundaries in AZ31 alloy and new design of magnesium alloys as smart materials

• Strong {0 0 0 1} <1 0 –1 0> texture can be an advantage in wrought Mg alloys.
• Large reversible strains produced by successive compressive deformation in Mg alloy.
• Strong texture + {1 0 –1 2} twinning + compression profile Mg alloys as smart materials.

Attractiveness of magnesium alloys for structural applications is caused by their intrinsic properties i.e. low density and high specific strength. The main challenge in development of magnesium alloys is connected with requirement to fulfill the main function of structural materials i.e. to bear load. Wrought magnesium alloys possess strong basal texture which causes anisotropy of mechanical properties. It would be interesting to find out the way how to benefit from this anisotropic behavior of magnesium alloys. One way is to take into account strong basal texture and {1 0 –1 2} twinning in magnesium alloys under compressive deformation. Parallelepiped samples of AZ31 magnesium alloy were successively deformed in compression with 3.5% strain along two perpendicular directions. During first compression the sample contracts along the RD direction parallel to compression axis, elongates only in one perpendicular ND direction and no deformation is observed in third perpendicular TD direction. Subsequent compression along the ND direction recovers the initial shape of the sample. Microstructure analyses shows that the {1 0 –1 2} twinning is the main deformation mode during compression along the RD direction and twin variants which gives 0% strain to TD direction are predominant in microstructure. Twin-free microstructure is observed after subsequent compression along the ND direction. Crystallographic analyzes and calculations explain why reversible motion of twin boundaries is more favorable than nucleation of other twin variants in matrix grains during compression along the ND direction. The experiment presented in this article profile wrought magnesium alloy as smart material and emphasize the importance of strong {0 0 0 1} <1 0 –1 0> texture and {1 0 –1 2} twinning in obtaining the properties characteristic for smart materials. In the presented case, it is the ability to produce and recover significant strains in a controlled manner under compressive stress.