Microstructure And Properties Of As-rolled Mg-Li-Sn Alloy

Mg-Li alloys as the world’s lightest structural material,its excellent mechanical properties get more and more attention by many researches.Magnesium alloy sheets can be widely used in the automotive,aerospace and 3C digital area,but the big problem is the lack of study on its rolling process.In this paper,the Mg-8Li-3Sn alloy was used as the research materials,and the homogeneous heat treatment mechanism and rolling deformation behavior of the alloy were studied.In this article,we mainly use the vacuum induction melting furnace with Ar gas protection,inductively coupled plasma spectrometer(ICP),dynamic mechanical analyzer(DMA),X-ray deflection,universal testing machine,optical microscope(OM),Micro-hardness tester,scanning electron microscopy(SEM),vacuum heat treatment furnace,55 t test rolling mill and other equipment.The microstructure,mechanical properties and rolling texture of alloy cast,heat treatment and rolling alloys were studied and analyzed.The results show that the microstructure of the as-cast Mg-8Li-3Sn alloy is composed by α-Mg phase,β-Li phase and flake or granular Li2 MgSn / Mg2 Sn precipitated phase,in which the α-Mg phase is a packed hexagonal structure(HCP),β-Li phase is the body-centered cubic structure(BCC),most of the precipitation phase is distributed in the grain boundary,a small amount of distribution in the grain inside.The tensile intensity σb,yield intensity σs,elastic modulus E,elongation δ and Vickers hardness of the as-cast alloys were 132.39 MPa,77.59 MPa,51.2GPa,20.15% and 49.9HV,respectively.It was found that the α-Mg phase in the alloy started to spheroidize at 300 ℃ with the increase of the heat treatment temperature,and the hardness of the alloy decreased due to homogenization heat treatment.And the precipitation phase in the alloy did not change significantly.At 300 ℃,the heat treatment of the alloy found that with the heat treatment time in the alloy α-Mg spheroidal growth.It was found that the best annealing heat treatment process conditions with the alloy was 300 ℃,8h.The results show that the alloy has the best comprehensive mechanical properties when the alloy is rolled at 225 ℃ with a single reduction rate of 60%.Through the analysis of the macroscopic morphology,microstructure and mechanical properties of the alloys,it is found that the rolling schedule of the alloy is 300 ℃ and the rolling pass is 5 pass.The tensile intensity,yield intensity and elongation of the alloy are both higher than that of the cast.The macroscopic texture of the alloy was analyzed by X-ray diffraction.It was found that the α-Mg phase of the rolled alloy is(0002)base texture,the β-Li phase is(110)crystal texture and the texture intensity in the alloy is weaker than that of the conventional magnesium alloys.With the increase of the rolling reduction rate,the texture intensity first becomes stronger and then stable.The rolling pass and rolling temperature can’t change the texture type of the alloys,but have some influence on the texture intensity.