| The 5000 series aluminum alloy is the best system of corrosion resistance and mechanical properties of aluminum alloys.Alloying of Zn elements is regarded as an effective way to improve the corrosion resistance and mechanical properties of the alloys.In this paper,the effects of Zn and Mg content on the microstructure and properties of the 5000 series aluminum alloy under the three gradients were investigated.The main research contents and conclusions are as follows:(1)The effect of adding 0.7% Zn on the microstructure and properties of Al-3.5Mg alloy forged material was studied.The results show that 0.7% Zn can improve the mechanical properties and intergranular corrosion resistance of the alloy,the hardness increases by 5.8 HV to 114.2 HV,the tensile strength increases by 22.5MPa to 395.2 MPa,the elongation increases 1.38% to 11.38%,the maximum depth of intergranular corrosion is reduced from 81.09 to 70.51 ?m.The subsequent 300 ?×4 h anneal reduces the dislocation density,hardness and tensile strength increase the elongation at break and intergranular corrosion resistance of alloy.(2)The effect of 4 kinds of alloy adding 1.3-1.6% Zn on the microstructure and properties of low medium Mg content 3.0-4.0%(5086 type)alloy hot rolled was studied.The results show that with the increase of Zn and Mg content,the hardness increases to 92.5-120.43 HV,tensile strength increases to 329.4-367 MPa,the elongation is 11.76-17.53%,the intergranular corrosion depth is reduced from 44.04?m to 111.31-145.22 ?m;1.44%Zn is added to Al-4.0Mg,the hardness is 120.43 HV,tensile strength is 367 MPa,the elongation is 14.12%,the maximum depth of intergranular corrosion is 120 ?m;the hardness and tensile strength of the alloy are reduced in the annealing at 250 ?×2 h,,and the corrosion resistance of the alloy is improved.The corrosion resistance of the alloy is not improved by the addition of Zn after annealing,the grade of intercrystalline corrosion is 3,and the anti peeling corrosion grade is P grade.(3)The effect of 3 kinds of alloy adding 1.6-1.8%Zn on the microstructure andproperties of medium Mg content 4.0-5.0%(5083 type)alloy hot rolled was studied.The results show that with the increase of Zn and Mg content,the hardness increases to 127.35-133.6HV,tensile strength to 392.2-432.8MPa,the elongation is11.18-14.12%,the maximum depth of intergranular corrosion is reduced from 41.62 to 123.5-171 ?m;1.83% Zn is added to Al-4.76 Mg,the hardness is 127.35 HV,tensile strength is 432.8 MPa,the elongation is 14.12%,the maximum depth of intergranular corrosion is 171 ?m.The hardness and tensile strength of the alloy are reduced when annealing at 250 ?×2 h,and the intergranular corrosion resistance is improved.After annealing,the maximum depth of intergranular corrosion is reduced,the improvement effect of anti peeling corrosion resistance is general.(4)The effect of 4 kinds of alloy adding 2.1-2.4% Zn on the microstructure and properties of high Mg content 5.0-6.5%(5A06 type)alloy hot rolled was studied.The results show that with the increase of Zn and Mg content,the hardness increases to 131.54-139.26 HV,tensile strength increases to 407.5-466.9MPa,the elongation is11.18-14.71%,the maximum depth of intergranular corrosion is reduced from 52 to107.53-133.97 ?m;2.3% Zn is added to Al-5.9Mg,the hardness is 139.26 HV,tensile strength is 466.9 MPa,the elongation is 12.35%,the maximum depth of intergranular corrosion is 133.97 ?m.Subsequent 250 ?×2 h annealing reduces the hardness and tensile strength of the alloy and increases the intergranular corrosion resistance to 3.After annealing,the intergranular corrosion depth of the alloy is reduced to 30-55 ?m from 139.26 ?m,the corrosion resistance and electrochemical corrosion properties of the alloy are significantly improvement.In this paper,the corrosion resistance of the alloy has been successfully improved by adding the Zn content,and the mechanical properties are also improved,which provides a scientific basis for the research and development of high corrosion resistance and high strength 5000 series aluminum alloys. |
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