Effect of pre-compressive strain on microstructure and mechanical properties of Mg-2.7Nd-0.4Zn-0.5Zr alloy

The effects of cold plastic pre-compression between solution treatment and artificial aging on the microstructure, mechanical properties and fracture behavior of the Mg-2.7Nd-0.4Zn-0.5Zr alloy were investigated by tensile test, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The high density of dislocations and twins formed through induced the pre-compressive strain ranged from 0% to 10%. As compared with specimens without strain, the pre-compressed specimens presented a higher number density of precipitates after the aging treatment. The specimen with strain of 8% contained not only plate-shaped precipitates but also vermicular precipitates and twins in the matrix. Tensile test results showed that pre-compression enhanced the strength of the aged alloy but reduced the ductility. As the strain increased from 0% to 8%, the UTS largely increased from 240 MPa to 315 MPa. Tensile fracture surfaces of specimens subjected to the pre-compressive strain mainly exhibited a trans-granular cleavage fracture. The size of cleavage planes decreased with the rise in strain level. This work indicated that a small amount of strain can further increase strength of alloy and also effectively enhance the formation of precipitates, which can expand the application fields of this alloy.