To further confirm the second phase

To further confirm the second phase change deducing above with Er addition, the TEM observation is used. The phase morphology and corresponding SAED of LZ105 alloy are shown in Fig. 4. Fig. 4a shows that the dispersed α-Mg phase whose diffraction patterns are indexed consistently according to a HCP structure can be detected by TEM. What's more, the MgLiZn phase is also be found in LZ105 alloy which is face-centered cubic (FCC) structure in Fig. 4b. Fig. 5a, b show the morphology and SAED pattern of W-phases in the LZ105-0.5/3.5Er alloys. The SAED pattern shows the massive phase has a FCC structure with a lattice constant (α) of ~0.676 nm through analyzing and calculating. The EDS result in Fig. 5c further confirms the composition of W-phase in Fig. 5b is Mg33.36Zn45.39Er21.25. Thus the W-phase with a Zn/Er ratio of about 2 in LZ105-xEr alloy is confirmed.In order to explore the second phase distributions in LZ105-xEr alloys, SEM analysis results are shown as followed. Fig. 6 show the magnified SEM images of the secondary phases in the LZ105, LZ105-1Er and LZ105-3.5Er alloys. The corresponding EDS results are listed in Table 2. Concretely Table 2 shows different percentage composition of the elements at the eleven selected points in these three alloys. Varied composition is attributed to different solubility rate of the elements and the strength of the bonds between the various elements. In LZ105 alloy, the particles (labeled as A, B and C) are Mg-Li-Zn phases considering the invisibility of Li element in SEM and the diffraction peaks in XRD pattern. The Mg-Li-Zn phases are mainly distributed along the grain boundaries and some other particles are located inside the grains.Fig. 6b shows Mg-Zn-Er phases (labeled as E, F) appear and the size and amount of Mg-Li-Zn phases (labeled as G) whose tiny amount of Er may come from matrix along the grain boundaries both become smaller with Er addition. In Fig. 6c, more Er addition leads to the formation of bulky Mg-Zn-Er phases (part of these phases labeled as I, J and K) in LZ105-3.5Er alloy. In addition, a good portion of these Mg-Zn-Er phases are located in the grain boundaries. Because of high Er addition, Mg-Li-Zn phase is hard to be found in LZ105-3.5Er alloy. The Zn/Er ratio in these Mg-Zn-Er phases is all around 2 calculated through the data in the Table 2 which can be confirmed as W-phase according to the above results. What's more, compared with the Zn content in the matrix in LZ105 and LZ105-1Er alloys (labeled as D and H), the dissolution of Zn solutes in the matrix decreases with addition of Er content due to the formation of Mg-Zn-Er particles. Fig. 7 show SEM micrographs of LZ105-xEr alloys. Through discussing above, it can be deduced from Fig. 7 that the number of Mg-Li-Zn phases decreases and Mg-Zn-Er phases which are mainly W-phases appear with Er addition. What's more, further increasing Er content makes the morphology of Mg-Zn-Er phase from tiny and nubbly to coarse and strip-like. Thick Mg-Zn-Er phase instead of Mg-Li-Zn phase is mainly distributed along the grain boundaries in LZ105-3.5Er alloy.