| Aimed at the national 973 project, the effects of elements and heattreatment on microstructure and mechanical properties, such as o b, and6 under room temperature were studied systematically by means of OM, TEMand SEM. The mechanism of above effects was analyzed. Results of the studyare as follows:(1) The microstructure of as-cast Al~9.OZn-2.5Mg-l.lCu-0.15Zr alloy containing 0. 12% Sc is equiaxial grain. The grain size of the alloy 2* is finer than that of the alloy 1*. After extruded, solutionized and aging, its grain structure is fiber structure. Obviously, containing 0. 12%Sc can enhance the temperature of recrystallization. The mechanical properties of the alloy 2* are higher than that of the alloy 1* at various heat treatment. Increase of o ?is 39. 4MPa, 28. 6 MPa at RRA, T76 respectively. Increase of 8 is unconspicuous. The electric conductivity and stress corrosion susceptibility can be increased because of the addition of 0. 12% Sc.(2) The tensile strength and elongation of the alloy 4* with 0. 20%Sc is much higher than that of the alloy 2* with 0. 12%Sc. Strengthening caused by increase of the content of Sc mainly comes from fine-grain strengthening and Al3(Sc, Zr) particle precipitation strengthening.(3) Enhancing the content of Zn can increase the strength and reduce elongation of Al-9. OZn-2.5Mg-l. 2Cu~0. 15Zr alloy. Increase of o b of the alloy 3" with 9. 38% Zn is 45. 5MPa, 15. 3 MPa, 23. 5MPa at solutionized, T6, T76 respectively. Reduction of 5 of the alloy 3* is 4. 23%, 1.79%, 0.53% at solutionized, T6, T76 respectively. After strengthening solution and T6, ob of the alloy 2", 3* is 829. 4MPa, 818. 6MPa respectively, 6 of the alloy 2", 3* is 5.68%, 5.38%. Obviously, strengthening solution can make the alloy obtain good combination properties. Enhancing the content of Zn can reduce the electric conductivity and stress corrosion susceptibility of Al-9. OZn-2. 5Mg-l. ICu-O. 15Zr alloy.(4) The increase of strength of alloys is accompanied with the decrease of elongation percentage with extendion of single aging time. But, thechange of strength and elongation is reverse after 22h. The strength of alloys reach peak while elongation is mininum at 22h. At the condition of T6 (120X22h), ob of the alloy l, 2, 3, 5 is 733. 2MPa, 763. 7MPa, 778. 4MPa, 812. 4MPa respectively, 8 of the alloy I, 2, 3, 5 is 5.28%, 5.68%, 3.79%, 5.60% respectively.(5) After aging at 160 for 16h which is the second aging of two-step aging, the alloy 2* obtains good combination properties, o b is 535. 9MPa,6 is 10.20% and the electric conductivity is 23.9 Ms/m.(6) When retrogression of RRA is 180 X30min, the alloy 2obtains good combination properties, ob is 733.4MPa, 5 is 5.4% and the electric conductivity is 21.8 Ms/m. |
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