The Research Of Discipline Of Grain Size And The Second Phase Of Magnesium Alloy AZ80on Mechanical Properties

Magnesium and magnesium alloy is the lightest metal material to this day, which densityis only1.74g/cm3, and it has high specific stiffness and strength, good cushioning ability,good heat conductivity and so on. Because of lots of advantages it is widely used in aviation,aerospace, automotive, computer, communications and home appliances and other industries,which was hailed as “21st century green engineering structure materials”. wroughtmagnesium alloys will be important structural materials in the area of air and land transport ormilitary project. In addition, the casting products can not replace wrought magnesium alloyslike plate, rod, tube.This paper used thermal treatment to change the performance of wrought magnesiumalloy AZ80. And it was also did the other experiments that were metallographic experiment,XRD diffraction analysis, and mechanical property test. The result showed that:（1） yield strength of magnesium alloy AZ80decreases with the increasing of averagegrain size, and through the verification, yield strength and grain size have a good linearrelationship, that conforms to Hall-Petch, and calculates k^（1）=373.41, σ₀^（1）=94.11, but therelationship between the tensile strength, hardness and grain size was not applicable toHall-Petch. In addition, elongation rate increases with the increasing of gain size, and studiedout the linear relationship δ=σ₀^d+pd², that to analyze, elongation rate and grain size aresignificantly linear correlation, and calculates p=0.007，σ₀^d=5.08.（2） when the temperature of aging treatment of AZ80magnesium is lower than160℃, βphase like graininess distribute on α-Mg substrate, it was named “T6-1”, when thetemperature of aging treatment is higher than160℃, β phase will gather on the substrate asstrips or slices, and occupies most of grain, it was named “T6-2”.（3） In “T6-1”, both yield strength and tensile strength decrease with the increasing ofaverage spacing of the second phase. And through the verification, yield strength and the spacing have a good linear relationship, that conforms to σ=σ₀+kλ^-1, and calculatesk^（5）=19.39，σ₀^（5）=150.76. tensile strength and the spacing are significantly linear correlation,which conforms to σ=σ₀+kλ^-1,and calculates k^（6）=43.07，σ₀^（6）=248.93. but hardness was notapplicable to σ=σ₀+kλ^-1. In addition, elongation rate increases with the increasing of thespacing, and studied out the linear relationship δ=σ₀^λ+mλ, that to analyze, elongation rate andthe spacing are significantly linear correlation, and calculates m=1.69，σ₀^λ=9.56. In “T6-2”,through the analysis of the effect of between mechanical properties and hardness and thevolume fraction of second phase, the linear equation σ=σ₀+kζ^1/2is studied out. The result wasshown tensile strength was fit for σ=σ₀+kζ^1/2, and calculates k^（10）=6.22，σ₀^（10）=278.84, butyield strength and hardness were not. Finally, elongation rate decreases with the increasing ofthe volume fraction, and studied out the linear relationship δ=σ₀^ζ+nζ^-1/2, which to analyze,elongation rate and volume fraction was fit for δ=σ₀^ζ+nζ^-1/2, and calculates n=9.98，σ₀^ζ=6.67.The result takes a good effect on the research about the linear correlation between grainsize, the spacing of the second phase and volume fraction of the second fraction andmechanical properties of magnesium alloy AZ80, and has certain guiding significance aboutpractical application in the future.