Abstract:The microstructure evolution and strengthening mechanisms of Mg-10Gd-1Er-1Zn-0.6Zr (wt.%) alloy were focused in the view of the size parameters and volume fraction (f_p) of dual phases (long period stacking ordered (LPSO) structures and β′ precipitates). Results show that two types of LPSO phases with different morphologies formed, and the morphology and size of both LPSO phases varied with the solution conditions. However, the volume fraction decreased monotonously with increasing solution temperature, which in turn raised the volume fraction of β′ phase during aging. The alloy exhibited an ultimate tensile strength of 352 MPa, a yield strength of 271 MPa, and an elongation of 3.5% after solution treatment at 500 °C for 12 h and aging at 200 °C for 114 h. In contrast to the LPSO phase, the β′ phase seems to play a more important role in enhancing the yield strength, and consequently, a decreased f_LPSO/f_β′ ratio results in an increased yield strength.

Key words: magnesium alloys; heat treatment; long period stacking ordered (LPSO) structures; precipitate; mechanical properties