Study On Microstrucure And Properties Of Magnesium-lithium Alloys By Ultrahigh Pressure Treatment

The development of high-performance,affordable and lightweight structural metals is an important goal to achieve high energy efficiency.Magnesium alloy is currently the lightest structural metal with abundant reserves.At the same time,magnesium alloy also has the advantages of high specific strength,good casting performance,recyclability and biocompatibility,which makes magnesium remarkable talent in automotive,aerospace and biomedical applications.However,the disadvantages of magnesium alloy such as low strength and poor plasticity limit its practical application.Ultra-high pressure treatment is a process specially used to develop new high-strength materials,and it is one of the effective means to regulate the structure and performance of materials.In this paper,the lightest density magnesium alloy Mg-Li alloy is selected to study the effect of ultra-high pressure treatment on the structure and properties of this alloy.In this paper,by ultra-high pressure treatment of Mg-13 Li alloy(wt.%,all compositions given hereinafter in wt.%),a layered double compressed twin structure is obtained.This nano-scale structure has a stable interface,forming a staggered grid structure,which hinders the movement of dislocations.The ultra-high pressure alloy has excellent yield strength(205.32 MPa)at room temperature,which is 3.76 times higher than that of as-cast alloy(43.11 MPa).In order to achieve a better interface strengthening effect,a large number of dislocations are formed by cryogenic rolling in the Mg-13 Li alloy,and then subjected to ultra-high pressure treatment to form a unique layered compressed twin-fault structure.Not only does it effectively avoid the de-twinning process,but also obtains a higher proportion of coherent interfaces.The synergy of twins and stacking faults has a higher strength than the structure with only twins.The yield strength(302.76 MPa)of the cryogenic-rolled ultrahigh-pressure alloy at room temperature has been further improved than that of the as-cast ultrahigh-pressure alloy,which is 6.02 times higher than that of the original as-cast alloy,surpassing the current commercial deformed magnesium alloy.In addition,through ultra-high pressure treatment,the nano-precipitated phases that are completely coherent with the matrix and precipitated at the twin boundaries provide additional pinning effect,and hinder the migration of the twin boundaries,and prevent the twins from widening and make the material Maintain higher strength without reducing the plasticity of the alloy.It can be seen that the ultra-high pressure process is an effective method to control the microstructure of magnesium alloys and improve the mechanical properties of magnesium alloys through interfaces strengthening.