Microstructure And Mechanical Properties Of Mg-Al-Zn-Nd Alloy Prepared By Solid State Synthesis

In the trend of "lightweight of material",magnesium alloy has been being widely used in the fields of aerospace,aviation,automotive,home appliances,communications and so on.With the application of magnesium alloy going up,more leftovers and offcut come out.Common smelting recovery methods cost too much,and smelting will arouse abundant wastage,garbage and poisonous gases,which would pollute the environment.This paper adopts the method of solid state synthesis to make magnesium alloy for the solutions that can realize the sustainable development of magnesium industry.This paper takes the most common AZ31B chips wrought mag'nesium alloy and AZ91D chips cast magnesium alloys as raw materials,makes use of the method of solid state synthesis separately make Mg-Al-Zn-Nd with Mg-Nd interalloy leftovers.The concrete crafts are cold-pressed compact and extruded heatedly.This paper studies the components of the alloy,the evolution rules of the structure,mechanical properties of the alloy and fracture behavior,as well as discussing the strengthening mechanisms and fracture mechanism of the alloy in the condition of solid state synthesis.This paper studies the basic trans-shaped features of AZ31B magnesium leftovers and Mg-Nd interalloy leftovers in the process of solid state synthesis.The study results show:in accordance with the proportion of containing Nd quality are 2%,2.5%,3%and 3.5%to make solid state synthesis with AZ31B magnesium chips,when Nd content is 3%,the solid state synthesis sample has good comprehensive mechanical properties with 3.85%of percentage elongation and 235MPa of tensile strength.Even Mg-Al-Zn-Nd in component and form comes out of five times of solid state synthesis with 3%of Nd content sample.As the pressed times increase,Mg-Nd interalloy chips are pressed more and more tiny and scattered,the squeezing linear becomes more and more disorderedly and tiny,the dynamic recrystallization is more and more entire,the percentage elongation and tensile strength become bigger.The addition of the rare earth element Nd causes changes in the crystal structure and stacking fault energy of the alloy,and improves the plastic deformation ability of the magnesium alloy.The continuous dynamic recrystallization increases the barrier effect of the grain boundary on the dislocation,which makes the dislocation unable to move,causing a large number of dislocations to accumulate near the grain boundary.The fine master alloy particles distributed on the grain boundaries also promote the accumulation of dislocations near the grain boundaries.At the same time and go up the top value in the fourth process with 12.01%of percentage elongation and 333MPa of tensile strength.The effect mechanism of solution treatment and aging treatment on the microstructure and mechanical properties of Mg-Al-Zn-Nd alloy synthesized by solid phase synthesis in 5 passes was studied.After analysis,it is concluded that after solution treatment,?-Mg17Al12 phase can be dissolved into ?-Mg matrix,and only more than half of Mg-Nd master alloy particles are dissolved.The master alloy particles are not distributed much on the grain boundaries,and more than 2/3 have been dissolved into the grains.The short rod-shaped and needle-shaped A12Nd compound and the granular AlMn phase are not dissolved in the?-Mg matrix.After solid solution at 540 ? ×24h and aging at 250? × 16h,fine and dispersed precipitation phase Mg12Nd is distributed on the fracture.These precipitated relative dislocations play a role in pinning,so that the dislocation and slip energy can interact,thereby Improve its mechanical properties and produce better aging strengthening effects.This paper studies the bars after five phases of solid state synthesis based on the blending the AZ91D magnesium alloy chips and Mg-Nd interalloy chips in accordance with 3%of Nd content.The paper analyses the breaking rules and strengthening mechanisms of the interalloy chips in the process of five phases of solid state synthesis.The result shows:after five phases of solid state synthesis,Mg-Nd interalloy chips are broken,cut and separated into tiny and round particles,which are evenly along the squeezing linear with a more serious broken extent than AZ31B.The phase of ?-Mg17Al12 scattered lumpily on the crystal boundary,is gradually attenuated,decreasing the breaking force on the ?-Mg kinetosome.The interalloy particles after five phases of solid state synthesis are in the shape of balls with smooth surface,closely combined with the ?-Mg kinetosome to realize atomic metallurgical bonding.The small particles of Mg-Nd master alloy have good plasticity,good compatibility with matrix magnesium,similar elastic modulus,and insensitive to interfaces and defects in the material.When the material receives a load,it will not be the first to undergo plastic deformation at the interface,but first plastic deformation occurs at the magnesium alloy matrix and absorb a large amount of energy.The stress at the interface is released or partially released.When the load is transferred to the particles,the interface It is not easy to be destroyed,so that the strength of the material is improved.This paper studies the corrosion of AZ31B-3Nd after four phases of solid state synthesis and analyzes the influence mechanisms on corrosion aroused by the corrosion process and Nd.3.5%concentration of NaCl solution is adopted as the corrosion solution,and compared with the AZ31B ingot primary extruded sample,AZ31B chips primary squeezed sample and AZ91D-3Nd leftovers squeezed sample for five times.The conclusion is reached:The corrosion micro-morphology of the AZ31B-3Nd magnesium alloy sample after four phases of solid state synthesis has the lowest corrosion rate and has typical pitting corrosion characteristics,from the initial partial areas pitting to form the feature of network,and partial areas corroded to form the deep pits.Rare earth Nd is a surface active element,which can increase the electrode potential of the substrate and improve the corrosion resistance of magnesium alloys.Rare earth Nd will form a very stable rare earth oxide film during the corrosion process.These rare earth oxide films will cover the surface at the early stage of corrosion,acting as a protective layer and preventing the corrosion from extending to a deeper bottom layer.The comprehensive analysis result holds on the belief that the corrosion resistance of this sample is the best one.