Study On Microstructure And Mechanical Properties Of Mg-Li-Al-LPC Alloy

Mg-Li alloy are among the lowest density metallic materials.,It is not only higher the stiffness and the machine work performance,but also has a good damping capacity and anti-particle penetrate property.So,Mg-Li alloys are applicable to aerospace,communication and war industry,which would be likely to become a one of important light,intensity and environmental protection materials in the 21th century.Domestic and foreign experts and Scholars have a lot of studied on Mg-Li alloys at present,but it remains low intensity and poor corrosion resistance shortcomings,so which has greatly restricted the further development.In order to study on improvement of its strength and plastic,the test used the vacuum melting furnace and argon protection melting to prepared Mg-7Li-1Al-xLPC alloy.The effects of La-Pr-Ce mischmetal on the microstructure and mechanical properties of the testing cast Mg-7Li-1Al alloys have been investigated by means of mechanical property measurement,optical microscopy,scanning electron microscopy and X-ray diffractometer.Influence of the aging treatment on microstructure and mechanical properties of the test Mg-7Li-1Al-xLPC alloys have-been studied.Similarly,heat treatment strengthening mechanism of cast Mg-7Li-1Al-xLPC alloy and strengthening mechanism of La-Pr-Ce mischmetal cast Mg-7Li-1Al has also been discussed in depth.The main results are as follows:1.Rare earth compound Al₁₁La₃ is found in matrix when adding La-Pr-Ce mischmetal to Mg-7Li-1Al alloy.Another rare earth compound Mg₃La is found when mischmetal content is more than 3%.2.Plastic of alloy get good raise adding La-Pr-Ce mischmetal to Mg-7Li-1Al alloy.Extension of Mg-7Li-1Al-4LPC alloy reach to 68.5%,which is more 13 times than Mg-7Li-1Al alloy.Alloy plastic improvement depend largely on rare-earth which having good grain refinement role.3.With solution time expand,allα-Mg phase has been dissolved in matrix step by step,but rare earth compound phase hasn't been dissolved,merely a change in shape.4.Aging treatment could increase the strength of Mg-7Li-1Al-xLPC alloys. The lower the mischmetal content of Mg-7Li-1Al-xLPC alloy,the better the effect of strengthening.5.Alloy aging treatment in the early lead to distribute a dispersion of the needle-likeα-Mg precipitation.With aging time expand,the continuousα-Mg phase precipitate in the grain sector.In the latter part of aging,the needle of the original precipitation has obvious rough and even the ball,the mechanical properties of these alloys lead to the rapid decline.6.Mg-7Li-1Al alloy added 0.5%Y,will causeα-Mg phase to congregate.The state of as-cast and heat-treatment mechanical properties is lower than Mg-7Li-1Al-0.5LPC alloy.