Highlights
•Electropulsing treatment (EPT) was applied in the hot-rolled 7075 Al alloy.
•EPT can make the solid-solution in a very short time in the 7075 Al alloy.
•EPT will not induce the distortion and oxidation of the specimens.
•EPT + AA makes the nearly same mechanical properties compared with the traditional T6 treatment.
Abstract
Electropulsing treatment (EPT) can make the second-phase rapidly dissolve into the matrix in the 7075 Al alloy. Although EPT has the lower degree of supersaturation compared with the traditional solid-solution treatment (SST), the combined effect of the fine precipitates and grains after artificial aging makes the slightly higher strength than that of traditional T6 treatment.
The new solid solution technology—Electropulsing treatment (EPT) can quickly dissolve the second phase in the alloy matrix during the solid solution of the aluminum alloy, and the solution time is only 220ms. This new short-term solution method not only shortens the solution time of the aluminum alloy, but also improves the mechanical properties, and has important engineering value.
7075 aluminum alloy is known as "Aluminum King", and it is favored by the aerospace and automotive industries for its unique high strength and low density. In the existing heating furnace solid solution technology, the process time is about 30 minutes, which seriously restricts the improvement of the production efficiency of high-strength aluminum parts. On the other hand, people who have achieved excellence have always regarded improving mechanical performance as a design material. For 7075 aluminum alloy, a uniform precipitation phase is obtained after artificial aging, and the second phase strengthening can make the alloy have higher strength. It is well known that fine grain strengthening is also an effective method to increase strength. At this stage, the ultrafine grains produced by the large plastic deformation technology have surprisingly improved the strength of alloys. However, in the actual production of aluminum alloys, deformation will be used in conjunction with heat treatment. Mutually exclusive: heat treatment will coarsen the deformed grains. Therefore, how to develop a short-term solution treatment technology can shorten the solution treatment time and improve the mechanical properties of the alloy, which is a problem worthy of study.
In 2015, Xiaofeng Xu of Jilin University proposed the aluminum alloy electric pulse processing technology (EPT). This technology relies on instantaneous high energy input to shorten the solution time of 7075 aluminum alloy to 220ms, which attracted wide attention. Related papers were published on Materials Science & Engineering A with the title "Effect of rapid solid-solution induced by electropulsing on the microstructure and mechanical properties in 7075 Al alloy" to discuss and discuss the dissolution effect of electrical pulse treatment technology on tissue and mechanics in aluminum alloys The impact of performance.
The results show that the electric pulse treatment technology can significantly accelerate the solution process in 7075 aluminum alloy. Although compared with the traditional solid solution method, the supersaturation of the sample treated by pulse current is slightly lower, and the comprehensive effect of grain refinement and precipitation phase refinement caused by pulse current treatment is better. The sample is high. In addition, the process time of the pulse current treatment is less than 1s, which can avoid deformation and oxidation during the heat treatment of the material. Therefore, pulse current processing is a promising method to obtain rapid enhancement.
In this study, the traditional T6 treatment method of SST was used as a comparison. Figure 1 is the optical microstructure of the quenched 7075 aluminum alloy. After SST and EPT, it can be seen from the picture that recrystallization has occurred in the alloy. According to the statistics of grain size, it can be seen that due to the huge difference in heat treatment time, the grain size of the sample treated by pulse current is only 15 μm, while the grain size of the traditional solid solution sample is only 53 μm.
In general, the author proposes a new short-term solution solution, which not only shortens the solution time of aluminum alloy, has important engineering value, but also has improved mechanical properties. In addition, the mechanism of action of pulse current solution technology Also got a new understanding