Studies On Microstructures And Mechanical Properties Of Super-light LA141 Mg-Li Alloy

Magnesium-lithium alloys have been regarded as the most promising green engineering material in the 21st century due to its rich raw materials and excellent comprehensive performance.In recent years,magnesium-lithium alloys have been increasingly applied to aerospace,nuclear-power project,automobile and medical equipment.In those areas,magnesium-lithium alloys often appear in the form of complicated thin-walled component,usually obtained by superplastic forming methods because the methods of casting or machining often cannot satisfy the requirement.Therefore,through a certain heat treatment and deformation methods and developed a magnesium-lithium alloy with ultra-light super-plasticity and high strength,which has very important significance.This research choose the LA141 magnesium-lithium alloy as the material,and carry out of different temperature of aging treatment and equal channel angular pressing?ECAP?from1 pass to 4 passes were analyzed by OM,SEM and XRD,and the mechanical properties were tested at room temperature with strain rate of 1.5×10^-3S^-1,study the effect of different temperature,different extrusion times and different paths for microstructure and mechanical properties of magnesium-lithium alloy,sum up magnesium-lithium alloy strengthening mechanism,the following conclusions are obtained:?1?The original LA141 alloy mainly composed of?-Mg and?-Li and Mg₂Al₃,whose tensile strength was 152.28MPa,and the elongation rate was 11.91%.After aging treatment of different temperature,it is found that the aging can refine the alloy grain,and a new phase of LiMgAl₂ is produced,which increases the strength of the alloy.With the increase of aging temperature,the elongation of the alloy decreases.Considering the strength and plasticity,the best aging temperature of LA141 alloy is 225?.?2?After 1 pass of ECAP,the grain size of the sample was refined and the preferred orientation appeared,and the grain had a tendency to elongate along the extrusion direction.At this time,the alloy tissue is mainly composed of?-Li,?-Mg,Mg₂Al₃ and Al₁₂Mg₁₇.After 1pass of ECAP,the tensile strength and elongation of the sample were significantly increased,and the tensile strength increased from 152.2MPa to 171.4MPa,which increased by about13%,while the elongation increased from 11.9%to 13.2%and increased by about 11%.?3?With the increase of extrusion passes,the tensile strength and elongation of the alloy were both increased first and then decreased and then increased.Under A path,the tensile strength of the alloy was increased from 152.2MPa to 198.6MPa,with an increase of about31%,and the elongation rate increased from 11.91%to 18.63%,increasing by about 57%.Under the Bc path,the tensile strength of the alloy was increased from 152.2MPa to179.85MPa,with an increase of about 18.2%,the elongation rate increased to 18.05%,and the increase was about 52%.It can be seen that ECAP extrusion can significantly improve the mechanical properties of LA141 alloy.?4?The analysis and comparison of A and Bc,C three kinds of extrusion path,we can find that the grain refinement effect is obvious when the path A is pressed,and the grains and grain boundaries are seriously distorted after repeated extrusion;Bc path extrusion Since each pass extrusion weakens the effect of the previous pass shear deformation and restores the cell topography,the grain deformation under the Bc path is relatively uniform,but the grain refinement effect is weaker than the A path;the C path extrusion is used.At the same time,the grain refinement effect is obviously weaker than that of the A path.However,since the C direction has a change in the direction of each pass,the ability of the C path to obtain equiax grains is better than that of the A path.As a whole,the alloy sample squeezing effect is best under the Bc path.