Effect of rolling deformation on microstructure and mechanical properties of Mg-6Sn-3Al-1Zn alloy

Abstract

The Mg-6Sn-3Al-1Zn alloys treated with the solid solution were induced 25%, 45%, 65% and 85% rolling deformation at 400 °C, respectively. The microstructures of as-rolled magnesium alloys were analyzed by XRD, OM, SEM and TEM, the mechanical properties were also measured. The results revealed that the rolled Mg-6Sn-3Al-1Zn alloys were composed of α-Mg matrix phase and Mg2Sn second phase, Mg2Sn distributed at the grain boundaries and intra-grains. With the increasing of the rolling deformation, the volume fraction of Mg2Sn phase distributed at the grain boundaries firstly decreased and then stabilized, the average size of Mg2Sn phase firstly increased and then decreased, the Mg2Sn phase distributed inside the grains gradually transformed from a rod shape to a spherical shape, the volume fraction of the recrystallized grains gradually increased and the average size of the recrystallized grains early decreased and eventually almost unchanged. When the rolling deformation exceeded 25%, the value of tensile strength and Vickers hardness of the Mg-6Sn-3Al-1Zn alloys increased with the rolling deformation. However, when the rolling deformation exceeded 65%, the elongation of the magnesium alloys diminished, however, the strength of as-rolled magnesium alloys did not increase significantly when the amount of rolling deformation increased from 65% to 85%. The mechanical properties were the best when the amount of rolling deformation reached 65%. Meanwhile, the volume fraction and area of Mg2Sn phase distributed on the grain boundaries were 2.9%, 105.5 μm2, the volume fraction and average grain size of recrystallized grains were 87% and 2.2 μm, respectively. In addition, it was worth noting that the Mg2Sn phase distributed inside the grains was radically converted into a spherical shape, and the tensile strength, elongation, hardness of the alloy were 317 MPa, 13% and 77.52 HV, respectively.