Effect of High Y Addition on Microstructure and Mechanical Properties of Mg-2Zn-1Mn Alloy

The microstructure and mechanical properties of Mg-2Zn-1Mn-xY (x=0, 1, 3, 5, 7, wt%) alloy were studied by optical microscope (OM), X-ray diffractometer (XRD), X-ray fluorescence spectrometer (XRF), electron probe microanalyzer (EPMA), scanning electron microscope (SEM), electron backscatter diffractometer (EBSD), transmission electron microscope (TEM), and uniaxial tensile tests. Results show that the secondary phases of as-cast alloys are changed from Mg7Zn3 to Mg3Zn3Y2 and finally transformed to Mg12ZnY with the addition of Y element. Although Y addition hinders the dynamic recrystallization process and therefore refines the grains, the excess Y addition cannot further refine the grains. Meanwhile, the ductility of as-extruded Mg-2Zn1Mn alloy is increased and then decreased with the addition of Y element, which may be attributed to the synergistic effect of texture orientation and grain coarsening. Besides, the strength enhancement is mainly attributed to grain refinement strengthening and secondary phase strengthening. The Mg-2Zn-1Mn-7Y alloy has the optimal mechanical properties: the ultimate tensile strength is 357 MPa, yield strength is 262 MPa, and elongation is 14%.

Automated summary

The microstructure and mechanical properties of Mg-2Zn-1Mn-xY (x=0, 1, 3, 5, 7, wt%) alloy were investigated using multiple techniques. The addition of Y element resulted in a transformation of secondary phases and hindered the dynamic recrystallization process, leading to refined grains. However, excessive Y addition did not further refine the grains. The addition of Y element influenced the ductility of the alloy, with an initial increase followed by a decrease, attributed to the combined effect of texture orientation and grain coarsening. The strength enhancement was mainly attributed to grain refinement strengthening and secondary phase strengthening. The Mg-2Zn-1Mn-7Y alloy exhibited optimal mechanical properties with a ultimate tensile strength of 357 MPa, yield strength of 262 MPa, and elongation of 14%.