| Cryogenic treatment is a new method for modification of materials, and it has a number of distinct advantages compared to other methods, and has been applied more and more widely in the industrial production. But now the studies on the mechanism of cryogenic treatment of non-ferrous metal materials at home and abroad are not very thorough, are unilateral. Therefore this paper study on the cold treatment temperature on the microstructure and properties of aluminum alloy in detail, has a certain theoretical value and practical significance.This paper choose3105aluminum alloy as the research object. Using liquid nitrogen as a refrigerant, the cryogenic treatment of3105aluminum alloy specimen are used by the liquid and gaseous method respectively. The change rule of different cryogenic heat preservation time and cooling off drawing temperature on the mechanical performance and organizational of the specimen in three states (H19, H26, and O) are analyzed by means of room temperature tensile test, hardness test method, as well as optical metallographic microscope, transmission electron microscope and scanning electron microscope analysis methods, etc.According to the discussion and analysis of experimental results, we get the following conclusions:(1) After1h heat preservation, the recrystallization starting temperature of3105aluminum alloy used in the experiment is about325℃, Annealed at this temperature, significant changes have taken place in the mechanical properties of the aluminum plate. The full recrystallization temperature is about400℃, When the annealing temperature reaches or exceeds this temperature, the mechanical properties of the specimens are basically stable. Prolonged the annealing time, the recrystallization temperature will decrease.(2) When the annealing time is kept constant, It can be found that the grain size of3105aluminum alloy has a tendency increased with the increase of annealing temperature. It is is because that the nucleation rate N and nuclei growth rate G are increased when the annealing time is kept constant as the temperature increased. But the tendency of N increase faster than G with the rise of the annealing temperature, resulting in grain refinement.(3) Annealing system of half-annealed H26state of3105aluminum alloy used in the experiment is7h under315℃heat preservation and dead-full annealing is at450℃ for1h.(4) With the decrease of tensile test temperature, annealed aluminum alloy tensile strength are increased gradually, and the three tensile directions has the same change trend. But the elongation rate of O state aluminum alloy increases with the intermediate decreased tensile temperature decreased slightly, then gradually increased, and the elongation rate reaches a maximum at-100℃. The hardness values are increased with the decrease of temperature, and O state increased significantly. Because of the dislocation of the clutter distribution and tiny grain size, the strength and elongation rate of H26state aluminum alloy are improved after cryogenic treatment. After cryogenic treatment, the dislocation between the winding and value-added, small precipitation of the second phase is to improve the performance of the O state alloy.(5) Cryogenic treatment of3105aluminum alloy for different time, the obtained tensile strength and elongation rate show no significant changes. The hardness is to maintain the upward trend with the prolonging of the holding time, O state is the most obvious, she second is H26state, H19state show no significant changes, the rising trend is very small, and hardness value are significantly enhanced After a5min cryogenic treatment. After a certain time of cryogenic insulation, there will be a fiber fragmentation phenomenon in H19and H26state, while this phenomenon will not occur in O state, but there will be a tiny second phase in the interior of the crystal.(6) The deep drawability of O state3105aluminum alloy is better than H26state, and the deep drawability of aluminum alloy is better than the aluminum alloy after a24h cryogenic treatment. |
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