Research On Microstructure And Machanical Properties Of Mg-Mn-RE Extruded Alloys

Since entering the 21st century,resources and the environment has become the priority issues of sustainable development for human.Therefore,to save energy,resources that the production of green industrial has become the trend of the current world.At the same time,the rapid development of the automobile industry,making the research and development of light casting for vehicle has become an important area of research and development direction.Magnesium alloy is the lightest structural metal materials in the practical application now,which has many excellent unique features ,such as low density,high strength and stiffness,good properties of shock absorber damping,machining,casting and excellent properties of thermal conductivity,electromagnetic shielding,recovery of the advantages of renewable.therefore,a growing number of magnesium alloy products have been used in cars,communication equipment,aviation and aeroapace industry.Magnesium alloy material also become the most development and potential application of"green"engineering materials in this century.In the magnesium alloy,WE54 alloy has widely used on the aviation out of good general properties,but recently because of the long-term place in high temperature of 150℃lead to unacceptable plastic.Aviation has already used WE43 replaced WE54 alloy.WE43 alloy containing low content of the Y element and enhance the content of the Nd element in the mixed rare earth. This paper analyzed the influence of adding the Nd element and increases the Y element to the Mg-Mn-Y base alloy Cast structure. Adding the Nd element and increases the Y element have the refined grain function to the casting alloy; At the same time the paper used the extrusion craft to carry on distortion processing to the cast condition alloy. Discussed the influence of increase the Y element or the adding Nd element to the organization of the extruded alloy. The result indicated that increased the Y element can cause the alloy to have the obvious refinement, the crystal grain from 10μm reduce to 5μm, the compound quantity had the increase tendency in the alloy and the compound distributing along the extruded direction. Regarding the extrusion alloy of adding the Nd element, the grain refining around to 1μm, the compound had the tendency which increased obviously, the size in 2μm below, distributing along the extrusion direction, through XRD might determine that this compound was Mg12Nd and Mg41Nd 5 phase.The paper to extruded the alloy to carry on the variable speed pulling test under the different temperature.The result indicated the extrusion alloy of increasing the Y element has demonstrated the obvious strengthened effect contrast the base alloy on the room temperature,but the plasticity actually had remarkable reduction.The room temperature fracture presented the obvious cleavage fracture.This was because the increase of the solid solubility of the Y element suppresses the non-basic plane slipping to urge;The extrusion alloy of adding the Nd element demonstrated the moderate strengthened effect on the room temperature.The yield strength of the room temperature about 220MPa,but had demonstrated the acceptable plasticity.The elongation ratio of the room temperature in 25%(real strain)above.The fracture presented the massive isometry strong nest shape,compared the strong nest with the base alloy tiny even.The yield strength alloy with adding or increasing the rare earth element has the large scale enhancement under the room temperature and the high temperature.For the extrusion alloy which increases the Y element has higher intensity under the room temperature and the high temperature than the extrusion alloy which adding the Nd element.However,the yield strength of the extrusion alloy which increases the Nd element to be higher than other alloys when the distortion's temperature above 200℃.This indicated that the Nd element has the good effect on thermostable performance to the magnesium alloy.Three kinds of alloy's high temperature performance demonstrated that along with strain the stress appeared softened phenomenon.Especially for the extrusion alloy which adding the Nd element in the true stress strain curve still presented the characteristic of the word hardening when the test under 100℃. This alloy presented the denticle stress phenomenon when the pulling under 200℃.The stress sensitivity presented the negative value.It possible due to the dynamic strain aging,namely the melting alloying element proliferated to the slip dislocation region lead to hardened and the dislocated reply softened interaction under the high temperature and the stress fuction urged.When 300℃test that the true stress strain curve presented the phenomenon which the stress softened,which because of the crystal boundary slipping urged.Namely the dislocation which increased by the alloy distortion process was absorbed by the crystal boundary lead to the stress softened behavior to be higher than the strengthened behavior to create.This article studies the Mn-Mn-Y base extruded distortion magnesium alloy not only had the very tensile strength under the room temperature,and the limit yield strength has also achieved 180MPa.This alloy has displayed the very good plasticity under the room temperature and the hot conditions.Passes through to the frame and the camber beam intensity examination,proved that the passenger train sleeping berth which makes for the materials satisfies the use completely by B1 extruion magnesium alloy.Therefore overall evalustion factors of material's performance and cost,we use B1 alloy to produce the passenger train sleeping berth's main body material.