| Al-Zn-Mg-Cu alloy has the characteristics of excellent comprehensive performance,and is widely used in aerospace,weaponry and other fields.And the Si Cw reinforced aluminum matrix composite material with the aluminum alloy as the matrix usually also has good comprehensive performance.In this paper,five kinds of aluminum alloy components were designed independently,and Si Cw reinforced aluminum matrix composites were prepared by squeeze casting using the self-made aluminum alloy as the matrix.The preparation and processing technology,the microstructure and properties of aluminum alloy and aluminum matrix composites were studied.The main research contents and corresponding results are as follows:(1)The effects of alloy composition(Zn/Mg ratio and Ti content)and three aging systems(T6,T6I4 and RRA)on the microstructure and properties were studied about Al-3.5Mg-x Zn-1.22Cu-0.2Zr-y Ti.The research shows that after the solution treatment at 450 ? × 2 h + 460 ? × 2 h + 470 ? × 2 h + 475 ? × 2 h,when the Zn/Mg ratio of the alloy increases from 3.55 to 3.85,the grains of the alloy increase,the undissolved phases increase,the dislocation strength decrease,and the intergranular corrosion resistance all decrease.The hardness and electrical conductivity of the alloy under the three agings generally decrease first and then increase.The room temperature compressive strength also decreases first and then increases.When the Zn/Mg ratio is 3.85,the hardness and compressive strength reach the maximum.compressive strength of the alloy reach to maximum.When Zn/Mg is constant,as the content of Ti increases(0-0.88 wt.%),the recrystallization degree of the alloy increases,the undissolved phase increases,and the dislocation density and dislocation strengthening gradually decrease,and the intergranular corrosion resistance gradually decreases.The hardness and conductivity of the alloy under the three types of aging gradually decreased,and the compressive strength also gradually decreased.When the aging system changes from single-stage T6 to intermittent T6I4 to three-stage RRA,for alloys containing Ti,the hardness and compressive strength increase first and then decrease.The alloy aged at T6I4 stage has the maximum value and the maximum compressive strength is 738.42 MPa.For the three alloys that do not contain Ti,their hardness and compressive strength first decrease and then increase,reaching the maximum value under T6 aging,and the maximum compressive strength is 815.23 MPa.(2)The process of preparing Si Cw-reinforced aluminum matrix composite materials by squeeze casting(mainly including preform preparation,sintering and squeeze casting processes)was studied.Studies have shown that the use of mixed colloids of aluminum phosphate and sodium silicate when preparing the preform solution can ensure the low temperature and high temperature adhesion of the preform at the same time.The multi-stage sintering process can gradually increase the temperature of the preform during sintering to prevent the preform from cracking.During the squeeze casting process,the preheating temperature of the mold cannot be lower than 300 ? to avoid the rapid solidification of the aluminum liquid caused by the temperature being too low,causing the preformed parts to not be penetrated during squeeze casting.The squeeze pressure of squeeze casting should be 100-150 MPa,and the holding time is 2-5min,in order to ensure the performance of the composite material and make the mold demold smoothly.(3)The microstructure of aluminum matrix composites and the effects of different aging systems T6-1(121?×5h)? T6-2(121?×2.5h)? T6I4-1(121?×2h(watercooling)+65?×48h)and T6I4(121?×4h(water-cooling)+65?×48h)on the performance of aluminum matrix composites were studied.The results show that after solution treatment of 450 ? × 2 h + 460 ? × 2 h + 470 ? × 2 h + 475 ? × 2 h,compared with the matrix,the aluminum matrix composite prepared by squeeze casting has smaller grain size,denser structure and higher dislocation strength.After aging treatment,the hardness of the aluminum-based composite material is also higher than that of the base alloy,and the electrical conductivity is lower than that of the base alloy.When the aging changes from T6-2 to T6-1,the composite's electrical conductivity gets decreased,the hardness increases,and the compressive strength at room temperature increases from 583.68 MPa to 728.77 MPa.When the aging T6I4-1 becomes T6I4,the composite's electrical conductivity gets increased,the hardness decreases,and the compressive strength at room temperature decreases,from 816.15 MPa to 631.80 MPa.Compared with the four aging systems in general,it is found that the mechanical properties of aluminum matrix composites are the best under the aging of T6I4-1,the hardness is 319.5HV,and the compressive strength at room temperature is 816.15 MPa.In summary,this article finds that for Al-3.5Mg-x Zn-1.22Cu-0.2Zr-y Ti aluminum alloy,when the Zn/Mg ratio varies from 3.55 to 3.85 and the Zn/Mg ratio is 3.85,the compressive strength at room temperature is as high as 815.23 MPa.Innovatively,Si Cw reinforced aluminum matrix composite material with 7000 aluminum alloy as the matrix was successfully prepared by squeeze casting.Its microstructure and performance were obviously superior to its matrix alloy. |
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