Effects Of Solution Process And Interrupted Aging On Microstructures And Mechanical Properties Of 7150 Aluminum Alloy

With the advent and development of industry 4.0 age, the traditional Al-Zn-Mg-Cu alloy was confronted with increasingly stringent requirements and more demanding service conditions from the aerospace industry, automotive industry, machinery industry, consumer electronics industry and so on. Therefore, the fundamental research of Al-Zn-Mg-Cu alloy cannot be relaxed, Further research were urgently needed to the appropriate technology, to make the best coordinate of alloy high-strength, high toughness, corrosion and fatigue resistance.7150 alloy was a high performance alloy of Al-Zn-Mg-Cu alloys. The solution treatment and aging treatment for aluminum alloy at the thickness of 45 mm thick as-rolled plate were studied sufficiently. The performance parameters of a series of alloy solution treatment and aging treatment was obtained by SEM, TEM, EBSD, room temperature tensile test and other methods. The appropriate solution treatment and aging treatment process were satisfactorily achieved by systematic comparing and analysis.The study on 7150 alloy solution treatment showed that, with the solution treatment temperature increasing and time gone by, the volume fraction of the second phase in the alloy matrix decreased and the alloy supersaturation increased. During the solution treatment, the alloy recrystallization fraction increased as the temperature rised and time gone by. When the temperature of isothermal solution treatment is 475℃, alloy recrystallized fraction show the trends of trends with "S" shaped curve. Recrystallization fraction is low within 2h in the beginning of the solution treatment, after more than 2h, alloy recrystallization fraction rapidly increased, reaching 11.87% at the time of 5h. The tensile properties of the alloy is proportional to the solution treatment temperature and time. However, when the temperature reached 475 ℃, the time reached 2h, recrystallization fraction increased, which reduced the strength of the alloy but the elongation still improved. The optimum process of 7150 alloy is 475 ℃ / 2h in single-stage solution treatment.Study on the alloy T6I4 interrupted aging process showed that, the pre-precipitation of the alloy is mainly GP zones at different pre-aging treatment and pre-aging temperature and time can affect the density of the precipitation phase. After a long stage at second-aging treatment, the alloy mainly contained GP zones with the size less than 5nm and η ’phase, and both the sizes approaching. η’ transition generated from the GP zone. The second-aging temperature can influence the peak position and peak aging. When the second-aging temperature was 85℃, the aging peak appeared earlier and the peak intensity was larger. After 65℃ aging treatment, the time that the peak appeared was later, or the peak strength of the alloy after aging 1800 h still raised. The temperature and time of pre-aging and second-aging effected the tensile strength and elongation of the alloy. which resulted that, when the aging treament temperature is 65 ℃ the tensile strength was about 10 MPa lower, but the elongation reached about 15%. Besides, The tensile strength and yield strength of the alloy at all interrupted aging treatment was closed to or exceed T6 state.