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Currently cryogenic technology, especially cryogenic technology has been widely used in industrial production, the main purpose of this study is the use of cryogenic treatment process to improve AlMnFe alloy microstructure and mechanical properties, in order to expand its field of use, extending its life. Experiments with liquid nitrogen as the refrigerant, the use of gas and liquid method AlMnFe method of aluminum alloy sheet sample cryogenic treatment. By tensile test, microhardness testing, XRD, TEM, SEM and other means of detection, study of different cold temperatures, cryogenic sample holding time on the properties and microstructure of aluminum sheet impact, identify and optimize AlMnFe alloy cryogenic process parameters, in addition also studied the deep cold pretreatment on aluminum sheet annealing organizational change and changes in tensile properties, while the low temperature performance AlMnFe alloy changes and anisotropy of some discussion. According to the experimental results of discussion and analysis, the following conclusions: (1) (deep) cold treatment temperature on AlMnFe alloy cryogenic after the performance and organization of the main problems: When cryogenic processing time is 1h, temperature of -196 ℃ when, AlMnFe alloy H18 , H26 aluminum sheet sample state tensile strength and elongation at room temperature and -50 ℃ lower than the temperature of the cold treatment has improved to some extent, indicating that this experiment should be optimal cryogenic temperature -196 ℃, but the study found AlMnFe O status alloy aluminum sheet mechanical properties before and after cryogenic treatment did not change significantly, more stable performance. This follow-up study for cryogenic treatment time on the properties of the alloy AlMnFe provide some experimental support; additionally state H26 aluminum sheet sample after cryogenic treatment -196 ℃ dislocation microstructure was messy like distribution inside the crystal, and the same Untreated aluminum sheet samples showed no obvious dislocation cells appear, and another black granular second phase precipitates, but relatively limited amount of precipitates concentrated. (2) cryogenic processing time on the AlMnFe insulation properties and microstructure of alloys is as follows: 0.1 mm thick AlMnFe alloy alloy sheet His -196 ℃ for 5 min after cryogenic treatment, a substantial increase in strength, ductility little change after 24h cryogenic , the strength increased to 265 MPa, elongation rate rose to 4.0%, are up to the maximum, optimum process for the cryogenic insulation 24h; cryogenic treatment can promote AlMnFe H18 alloy second phase precipitates, second phase precipitation can increase aluminum sheet hardness; cryogenic insulation 24h cause AlMnFe fibrous sheet aluminum alloy His state grain fragmentation, fragmentation after fine grain size in between 0.3 ~ 2.5μm; 0.1mm state of AlMnFe H26 alloy aluminum sheet through short-term cryogenic treatment, strength is also increased, an increase of around 7%, with the cryogenic holding time, strength is more stable; elongation with cryogenic treatment holding time, little change in the overall trend, but in the cryogenic heat 1h, the elongation larger increase by about 24%; H26 aluminum sheet by the state long after cryogenic treatment also appears H18 status similar situation, namely the phenomenon of broken crystal fiber, shredded fine equiaxed after size in 100 ~ 200 nm, while its grain morphology mostly quadrilateral or polygon. O status cryogenic sample after long grain fining does not appear the phenomenon, and its mechanical properties before and after treatment changed little. (3) pretreatment on AlMnFe cryogenic aluminum sheet annealed microstructure and properties of mainly as follows: When the aluminum sheet after 330 ℃ heat 3 ~ 7 h, the deep cold pretreatment their organizations more significant impact on the emergence of recrystallization delay the process of the phenomenon, and this phenomenon is pretreated with cryogenic more obvious extension of time; while mechanical properties of aluminum sheet pretreated by cryogenic impact, tensile strength, elongation and hardness has been changed . In addition, pretreatment can cause cryogenic aluminum sheet internal grain orientation changed greatly, when the aluminum sheets were incubated 7h 330 ℃ annealing process, Al grains in the (220) crystal plane orientation as cryogenic holding time extend substantially weakened, while in (111), (200), (311) crystal face orientation, etc. gradually strengthened. (4) AlMnFe alloy temperature performance mainly as: AlMnFe alloy sheet tensile strength and elongation of the overall trend is down with stretching temperature is increased, but the elongation at -50 ℃ ~ 100 ℃ between the minimum value, Subsequently rise and higher than room temperature elongation values. In addition to the low-temperature tensile fracture morphology of aluminum were compared and found that low temperature tensile fracture dimple organizations to increase. On the low temperature performance advantages of a preliminary theoretical analysis, the lower the temperature, the more difficult inside the crystal dislocation cross-slip phenomenon occurs, work hardening exponent increases, while cryogenic causes fibrous grain fining also one of the important factor.
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