Microstructure And Mechanical Properties Of Mg-Al-Ca-Mn Alloy Wires

The development trend of automobile industry in the future is lightweight.With the increase of automotive electronic equipment,the proportion of automotive wiring harness in automotive parts increases gradually,so the lightweight of automotive wiring harness becomes more and more important.As the lightest structural material available in industrial production,magnesium alloy is an ideal material for automobile weight reduction.Therefore,it is of great significance to develop lightweight and high strength magnesium alloy materials.In this paper,the initial material is Mg-0.98Al-0.15Ca-0.3Mn(at%)magnesium alloy ingot.The wire with diameter of 0.95 mm was prepared by extrusion,hot drawing and cold drawing with low alloying and high strength and toughness.In order to obtain Mg-Al-Ca-Mn magnesium alloy wires with good comprehensive mechanical properties,the effects of microstructure,heat treatment process and intergranular coordination on local strain were systematically studied.The results show that the grain boundary segregation occurs obviously,which not only helps to refine the grain,but also affects the dynamic recrystallization mechanism and weakens the texture.At the same time,a large number of nanoscale precipitates are dispersed in the matrix,which hinders the movement of dislocations and leads to dislocation entanglement.Therefore,the fine grain strengthening,grain boundary segregation strengthening and dislocation strengthening make the strength(?_0.2=394MPa,?_b=431 MPa)of?2.40 mm wire is higher than that of other wrought magnesium alloys reported.With the increase of annealing temperature or annealing time,the recrystallized grains grow gradually.The significant evolution of texture indicates that the grains with<2(?)(?)0>orientation grow preferentially.In addition,the homogeneity of recrystallized grains is improved and the grain orientation is gradually random.Uniform distribution of grains is beneficial to uniform plastic deformation,while random orientation of crystals is beneficial to coordinate plastic deformation and improve plasticity.Different solution processes have influence on the effect of age hardening.Under the heat treatment process of solution(500?/10 min)and aged(200?/45 min),the magnesium alloy wire has the best strength and plasticity matching.Due to the precipitation in the G.P region and the weakening of the basal texture,the yield strength of the wire increases and the ductility can be maintained after peak aging treatment,which is different from the general strength plasticity relationship.The results show that{10(?)2}tensile twins are formed when the aged wire is stretched at room temperature.The small grain size limits the formation of twins,so twinning is not the main deformation mechanism.The starting of the slip system is related to the Schmid factor and the geometric compatibility factor.The local strain distribution is inhomogeneous during the deformation process.With the increase of macro strain,the local strain distribution inhomogeneity first increases and then decreases.In order to coordinate the intergranular deformation,the basal-pyramidal slip transfer occurs,and the slip transfer is the main mechanism to coordinate the intergranular strain,and the orientation difference on both sides of the grain boundary has a significant effect on the slip transfer.