Effect of Quasicrystal I-Phase on Microstructure and Mechanical Properties of Hot-Rolled Diphasic Mg-8 wt.% Li Alloy

Abstract

The microstructure and mechanical properties of hot-rolled Mg-8 wt.% Li and Mg-8 wt.% Li-6 wt.% Zn-1.2 wt.% Y alloys were investigated, and it was demonstrated that due to the formation of the I-phase (Mg 3 Zn 6 Y, icosahedral structure), the crystallographic texture and strength of the alloys is weakened and increased, respectively. At different hot-rolled ratios, the anisotropy (plasticity) of Mg-8 wt.% Li alloy exhibits obviously stronger than the Mg-8 wt.% Li-6 wt.% Zn-1.2 wt.% Y alloy. Failure analysis indicated that ductile fracture occurs along the rolling direction (RD), while quasi-cleavage fracture occurs along the transverse direction (TD). Cracks in the Mg-8 wt.% Li were found to be mainly initiated at the a-Mg phase and the two-phase boundary, which were respectively generated by tensile testing along the RD and TD. The cracks in the Mg-8 wt.% Li-6 wt.% Zn-1.2 wt.% Y alloy were confirmed to be located in the rich Iphase region of the a-Mg phase and at the junction site of the matrix phases.

Effect of Surfactants on the Corrosion Protectability of Calcium Phosphate Conversion Coatings on Duplex Structured Mg-8Li (in Wt.%) Alloy

“…Due to low density, high specific strength, specific stiffness, ductility, good electromagnetic wave shielding capacity, and the improved preparation process [2][3][4][5][6][7][8], Mg-Li alloys have great application prospects. Moreover, their microstructure is closely related to the content of element Li [9][10][11][12][13][14][15][16], i.e., (1) when the content of Li is below 5.5 wt.%, the alloys are only comprised of α-Mg phase with hexagonal close packed (hcp) structure; (2) when the content of Li is more than 10.3 wt.%, the alloys are comprised of a β-Li phase with a body-centered cubic (bcc) structure; (3) when the Li content is in the range of 5.5-10.3 wt.%, the alloys have a typical dual-phase structure (α-Mg + β-Li), ensuring their higher specific strength and stiffness. However, micro galvanic corrosion easily occurs in the duplex structured Mg-Li alloys due to the potential difference at the α-Mg/β-Li interfaces, resulting in their poor corrosion resistance and limited applications [6,9].…”

“…Thus, it is quite necessary to improve the corrosion resistance of the duplex structured Mg-Li alloys. So far, there are commonly three kinds of methods for increasing corrosion resistance of Mg-Li alloys, including alloying, deformation processes, and protective coatings [6,9,[15][16][17][18][19][20][21]. However, these methods are difficult to be carried out and have a relatively limited effect for improving the corrosion resistance of Mg-Li alloys.…”