| Scandium as the most effective alloying elements in aluminum alloy found so far, Sc alloying make aluminium alloys shows excellent aging strengthening effect, high thermal stability and good mechanical properties. In this paper, the directly electrolytic process of Al-Sc aluminium alloy were investigated to over some problems such as high alloying cost, complicate produce process and so on. The potable electrolytic cell was designed and AI alloys with different Sc content was produced with this cell in the condition of the laboratory. The 2024 alloys with 0.4%Sc and 0.2Zr% were prepared. The solution process, presaging process and aging process were optimized. The effect of solution time, aging temperature, aging time, pre-aging temperature and pre-aging time on the microstructure and properties of 2024-Sc aluminium were investigated by metallographic microscoped, electron microscopy, hardness and tensile tests.Although the vertical bar type cathode electrolyzer in electrolytic experiment has a very simple structure, it has only 27% electrolytic efficiency. By conducting a serious structure redesign and electrolytic experiments, a potable electrolytic cell with suspended cathode electrolyzer was developed. The electrolytic efficiency can be over 80% whither it was used to electrolysis of pure aluminium or Al-Sc alloys. The potable electrolytic cell with suspended cathode electrolyzer is one the best cell structure.By optimizing the solution process using 2h,4h and solution time, a optimal solution process was decided, which is the samples need to be hold for 4 hours at 500℃. The samples treated with this process have the highest hardness.By optimizing the aging process using different aging temperature(170℃180℃,190℃,200℃) and different aging time (8h, 10h,12h,14h,16h,18h,20h), a optimal aging process was decided,which is the samples need to be hold for 18 hours at 190℃after solution treatment. The samples treated with this process have the highest peak hardness. By optimizing the pre-aging process using different aging temperature(110℃, 130℃,140℃) and different aging time (2h,4h,6h,8h), a optimal pre-aging process was decided,which is the samples need to be hold for 18 hours at 190℃before aging treatment and after solution treatment. The samples treated with this process have the highest peak hardness.According above optimization results, the final optimal heat treatment process of 2024 alloys with 0.4Sc% and 0.2Zr% can be determined, which is 500℃×4h+130℃×6h+190℃×18hg. The hardness of alloys treated with the optimal heat treatments is increased to 151HV, which is more then the hardness of alloys supplied with American supplier. |
PDF Full Text Request