Investigation On Forging Of Mg-Li Alloy

In this paper,the heat treatment system,thermal deformation behavior and forging forming process of Mg-8Li-1Sn alloy are studied respectively.Through the analysis of the as-cast microstructure and properties of Mg-8Li-1Sn alloy,it is found that the microstructure of the cast alloy is not uniform and the mechanical properties are poor.Therefore,the alloy has been studied by heat treatment.Heat treatment system was under the conditions of 3h,5h,8h,12 h and250 ?,300 ?,eight groups in total.After the heat treatment,the mechanical properties of Mg-8Li-1Sn were optimized at 300 ? and 8h after heat treatment.The elongation,tensile strength,yield strength and hardness were 4.68%,95.4 MPa,43.6MPa,46 HB respectively.At the same time,it was found that the ?-Mg striped structure was not completely refined and spheroidized,and some stripes structure were still present.In this paper,the thermal deformation behavior of Mg-8Li-1Sn alloy is studied.The results show that the high temperature flow stress of Mg-8Li-1Sn alloy is characterized by the decrease of the peak stress with the increase of the compression temperature and the increase of the compression rate.At the same time,the constitutive equations of the alloy under various stress conditions are calculated.The results show that the constitutive equation of Mg-8Li-1Sn alloy should be in the form of hyperbolic sine function.In this form,the stress and experimental results and its thermal activation energy is Q = 110.802 KJ / mol.According to the constitutive relation,the power dissipation diagram and the flow-loss diagram of the Mg-8Li-1Sn alloy are superimposed,than we calculated the processing map on the strain of 0.5and 0.7,found that the optimum processing area is 200 ?-225 ?,0.001 s-1-0.01s-1region,about 250 ° C and 275-300 ° C,the rate of 0.1s-1-1s-1 in the two regions,a total of three most suitable processing area.According to the processing map of Mg-8Li-1Sn alloy,different forging processes were developed.It is 250 ?,1-5 passes;300 ?,1-5 passes;350 ?,1-4passes respectively.Found that the mechanical properties of the third pass after the forging are the best,because the(0002)base texture of the alloy after 3 passes is the weakest,and the multi-direction forging can form different deformation zones,forging will weaken the deformation zone,so multi-forging can significantly refine the grain,improve the mechanical properties of the Mg-8Li-1Sn alloy.