| Considering the development of 7xxx series ultra high strength aluminum alloys in our country, the strengthening of aluminum alloys was studied.With the help of OM, SEM and TEM etc., the effects of small addition of Ag and heat treatment on the alloys microstructure and mechanical properties, such asσb andδunder room temperature, were studied systematically. The mechanism of above effects was analyzed. Results of the study are as follows:1. Small addition of Ag in the Al-4.5Zn-1.0Mg-5.5Cu aluminum alloy enhances the strength of this alloy, but simultaneously reduces the plasticity of this alloy. Small addition of Ag has accelerated the effectiveness for a period of time speed of response, but Ag joined also lengthens the alloy to arrive the intensity peak value the time.2. The strength of alloys increased with the increase of Zn content,, the peak-aged tensile strength of alloy 3 (Al-6.6%Zn-1.08%Mg-5.5 Cu) is 491.7MPa at T6 heat treatment, which is higher about 30MPa than alloy 1 (Al-4.35%Zn-1.05%Mg-5.7%Cu). The elongation of alloy reduced with the increase of Zn content, Due to the reduction is little; it is advisable that increase the Zn content in order to increase the strength of alloys.3. Increased magnesium content can improve the alloy strength, when Mg=1.55%, the tensile strength of alloy 5# (Al-4.45%Zn-1.55%Mg-5.3%Cu) is 461.1MPa, but still 25.5% of the plastic. Hence an appropriate increase in Mg content alloy is to improve the overall performance of an effective way.4. The 6 kinds of alloy after T6 and T8 heat treatment is studied, by mechanical properties, morphology, fracture characteristics analysis that is shows:T8 heat treatment make the organization is relatively fine, and has higher high strength than the alloy which is T8 heat treatment. |
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