Investigation on the Microstructure and Mechanical Properties of Mg-Al-Yb Alloys

Abstract

The effects of Yb addition on the microstructure and mechanical properties of Mg-5Al alloy are investigated. The results indicate that the addition of Yb to the Mg-5Al alloy facilitates the formation of a thermally stable Al 2 Yb phase, the refinement of the microstructure and the suppression of the volume fraction of Mg 17 Al 12 phase in Mg-5Al alloy. Yb addition has little effect on the mechanical properties of the experimental alloys tested at room temperature. At elevated temperatures, however, the ultimate tensile strength (UTS) is significantly increased by Yb addition and Mg-5Al-1Yb has the highest UTS value than other experimental alloys. On the other hand, the yield strength (YS) increases at all tested temperatures due to the grain refinement and dispersion strengthening of the secondary phase. Meanwhile, the elongation (") of the experimental alloys decreases at all tested temperatures. Tensile fractographic analysis indicates that cleavage fracture is the dominant mechanism of the Mg-5Al and Mg-5Al-xYb alloys at room temperature. At elevated temperatures, however, the fracture mechanism of experimental alloys mainly changes from cleavage to quasi-cleavage fracture.

Improved strength of Mg alloy extruded at high speed with artificial cooling

“…9a) that eventually led to cleavage fracture, as is seen in the many river-patterned cleavage planes in the fracture surface (Fig. 9d), which is not unlike the fracture surface of cast Mg alloys with large grain sizes [24]. Meanwhile, with the Water 2 sample, the fact that the DRXed grain size (10.1e18.9 mm) is comparatively similar to the width of non-DRXed grains (8e33 mm) means that twins are formed in both DRXed and non-DRXed grains (Fig.…”

Understanding the factors influencing yield strength on Mg alloys

“…This model has been applied to pure Mg [10,11,12,14], the binary systems Mg-Al [2,19], Mg-Zn [12,13,29], Mg-Sn [48], Mg-Y [5,11], Mg-Gd [33], as well as to higher order systems such as Mg-Al-Zn [51,52], Mg-Al-Yb [53] and Mg-Y-Gd [33]. The results are shown in the experimental vs. predicted σ Y plot in Figure 6, where the legend contains each composition together with its corresponding reference.…”

Microstructure Evolution of the Mg-5.8 Zn-0.5 Zr-1.0 Yb Alloy During Homogenization

“…The white eutectic phases with morphology of discontinuous networks or granules distributed along the α-Mg dendrite boundaries substantially degrade the mechanical properties of the alloy because of the hereditary microstructure. The grain refinement effect of Yb in magnesium alloys has been reported in many studies 9,11 . However, as shown in Figure 1, the typical dendritic grain morphology and large grain size of the cast microstructure reveal that the modification of Yb does not occur in the studied Mg-5.8 Zn-0.5 Zr-1.0 Yb as-cast alloys.…”

“…Furthermore, a morphological evolution of precipitates or secondary phases is achieved by adding appropriate amount of Yb [19][20][21] . Consequently, alloys with Yb modification exhibit enhanced performances in terms of mechanical properties 11,15,19 , corrosion resistance 13,18,22 , and thermal stability 10,21 compared with the unmodified counterparts.…”

“…The grain refinement effect is the most important function of Yb addition [9][10][11] . Unlike other elements, such as Zr in magnesium alloys or Ti in aluminum alloys, which increase grain coarsening resistance by heterogeneous nucleus in peritectic reaction 12 , Yb refines microstructures mainly due to constitutional undercooling 11 . Moreover, the precipitation strengthening effects of Yb-rich precipitates are the most promising approach to developing high-performance alloys.…”