Effects Of Mg And Rare Earth Element Nd On The Microstructure And Properties Of A380.0 Aluminum Alloy

A380.0 aluminum alloy is the main subject investigated in this paper, and the influnces of Mg and Nd elements seperately on the microstructures and mechanical properties under as-cast and T6 treatment conditions are studied by means of tensile strength,hardness,and elongation of the specimens.,he appropriate amount of Mg or Nd element is pursued. Phases composition,microstructures and fractography are studied by means of XRD,SEM,EDAX, which is heplful to study the interaction of the constituents in the A380.0 aluminumalloywith Mg or Nd element through the microstructures and macro-properties.Results indicate that with the addition of Mg between a certain amount, the phenomenon of grain refinement is obvious, Mg2Si phase is generated and distributed discontinuous in the grain boundary. Solution strengthening of the solid solution of Mg element in theα(Al) matrix,dispersion strengthening of the Mg2Si phase in theα(Al) matrix,precipitation strengthening of the intensified phases which can be under heat treatment,and the decrease of distance between secondary dendritic of the constitutional supercooling function of the enrichment of the Mg element in the interface of the liquid phase,all of these factors dramaticly improve the properties of the matrix alloys jointly. Tensile strength and hardness rise first and attain a peak and then descent according with the increment of Mg element.With the addition of 0.9%(wt)Mg,Tensile strength of the as-cast alloy get to the peak,is 195MPa,improved about 11.43% compared with the A380.0 aluminum alloy; Hardness is 81.9HV with the addition of 1.5% Mg, improved about 19.74% compared with the A380.0 aluminum alloy. After T6 treatment, tensile strength of the alloy is 207 MPa,Hardness is 86.4HV. Tensile strength.and hardness rise first and attain a peak and the descent according with the increment of Mg element,with the amount of 0.9%Mg, tensile strength gets to the peak,is 292MPa,improved about 41.06% compared with the matrix alloy under the same T6 treatment; with the amount of 1.5%Mg,hardness gets to the peak,is 153HV,improved about 77.08% compared with the matrix alloy under the same T6 treatment.With the addition of Nd element, not only did the microstructures of the alloys refined dramatically, but also the morphologies of the eutectic Si, Al9FeSi3 and Al3.21Si0.47 changed a lot, the needle and flake-liked phases changed to rod-liked phases, the edge of the intermetallic compounds changed to a round-liked morphology. The grain boundary scattered with the average arranging intermetallic compounds, all of this descend the stress concentration of the needle and flake-liked phases, which also dramatically rise the tensile strength and hardness of the alloy. With the addition of 0.5%Nd, tensile strength and hardness attain a peak of 217MPa and 99HV, which arise about 24% and 44.74% separately compared with A380.0 alloy. Mechanical properties descend with more Nd element. T6 heat tretment also improves mechanical properties dramatically, the trend of tensile strength and hardness of the alloys with the conditions of as-cast and T6 heat treatment remains the same, rise first and attain a peak and after then,a descent arrives.The active chemical property and the reduction function of the surface tension of the Nd element,which act as a modification effect of the eutectic Si,improve the morphology of the phases in the matrix alloys; On the other hand,the low solid solution of Nd element in theα(Al),which makes the element in the interface of the liquid phase,it prevent the diffusion of the Al atom,and all of this makes the refinement of the grain addition with the constitutional supercooling. Tensile strength and hardness rise first and attain a peak and then descent according with the increment of Nd element. With the addition of 0.5%(wt)Nd, tensile strength and hardness attain a peak,about 217MPa and 99HV respetively,improve 24% and 44.74% compared with matrix alloy.With the increment of Nd,the mechanical properties descend. Properties of the alloys improved dramatically after T6 treatment.Tensile strength and hardness rise first and attain a peak and then descent,with the addition of 0.5%Nd, tensile strength and hardness reached a peak about 301MPa and 197HV respectively, improved about 45.4% and 128%.