变形与热处理组合工艺对6061铝合金组织和性能的影响

发布时间：2018-07-10 01:14

本文选题：6061铝合金 + 变形　；参考：《江苏大学》2017年硕士论文

【摘要】：6xxx系铝合金因为具有低密度、高比强度和较好的耐腐蚀性,被广泛应用于航空航天、汽车制造等领域。随着对材料性能要求的提高,人们开始探索新的材料处理方式,以期获得良好的综合性能。本文以6061铝合金为研究对象,经不同变形与热处理组合工艺处理,研究变形、预时效和中间热处理方式对6061铝合金硬度、拉伸性能、电导率和耐腐蚀性等的影响,并从金相组织、断口扫描、XRD、透射电镜等方面对变形与热处理组合工艺处理后的试样进行微观组织结构分析,得出以下结论:(1)6061铝合金固溶处理(540℃、3h)后在时效温度为180℃、时效时间为4h时硬度最大,时效前的变形不仅能提高试样峰值时效的硬度和强度,还能减少到达峰值时效的时间,且形变量越大,硬度和强度越高,到达峰值时效的时间越短,但塑性降低;在形变量都为50%的条件下,变形前不经预时效处理的试样最终的硬度为129.6HV,抗拉强度为368.32MPa,延伸率为22.10%,变形前经预时效处理的试样最终的硬度为136.7HV,抗拉强度为385.82MPa,延伸率为22.21%,可以看出变形前的预时效不仅能提高试样的硬度和强度,还改善了6061铝合金的塑性;在总变形量相同的条件下,中间经过峰值时效的试样最终的硬度和强度最高,但塑性最差,中间经过再结晶处理的试样塑性最好,但强度较低,中间经过回复处理的试样最终的硬度、强度和延伸率介于两者之间。(2)固溶处理后的变形会降低6061铝合金的电导率,且变形量越大,降低越严重;变形后的时效过程中6061铝合金的电导率会随着时效时间的延长逐渐提高,回复和再结晶处理都能提高6061铝合金的电导率,且再结晶的作用更大。(3)时效前的变形能提高6061铝合金的耐腐蚀性,且变形量越大合金的耐腐蚀性越好;变形量相同的条件下,变形前的预时效会降低6061铝合金峰值时效后的耐腐蚀性;变形后经回复和再结晶处理的试样的耐腐蚀性要好于峰时效处理的试样,且再结晶处理的作用更显著,不同的中间热处理方式对6061铝合金最终的耐腐蚀性影响不同。(4)时效前的变形处理会使晶粒拉长,且变形量越大,晶粒拉长越明显,变形后的再结晶处理会细化晶粒;时效前的变形不仅影响时效后衍射峰的强度,还会使衍射峰的位置发生偏移,变形后的热处理方式只会影响6061铝合金最终衍射峰的强度,而对衍射峰的位置影响不大。(5)不同变形与热处理工艺下6061铝合金的拉伸断口都为韧性断裂,变形、预时效和中间热处理方式都会影响6061铝合金最终的断口形貌,时效前的变形量越大,断口处大韧窝的数量越少,韧窝越浅,塑性越差;变形前的预时效可以改善6061铝合金峰值时效后的塑性;变形后经过再结晶处理的试样晶粒细化,再经变形时效后,断口韧窝均匀分布,大韧窝的数量较多且韧窝较深,塑性较好。(6)时效前的变形会产生大量的位错,形变量越大,位错缠结越严重,且分布不均匀,变形量为50%时,产生形变亚结构;变形前经预时效处理的试样产生的形变亚结构更明显,且尺寸更均匀,塑性更好;变形后经回复处理,晶体中的位错密度略微降低,空位大量消失;变形后经再结晶处理,位错基本消失,再经变形又产生位错缠结,合金强度升高。
[Abstract]:Because of its low density, high specific strength and good corrosion resistance, 6xxx aluminum alloy has been widely used in aerospace, automobile manufacturing and other fields. With the improvement of the material performance, people began to explore new material treatment methods in order to obtain good comprehensive performance. This paper is based on 6061 aluminum alloy, through different deformation and deformation. The effects of deformation, pre aging and intermediate heat treatment on the hardness, tensile properties, electrical conductivity and corrosion resistance of 6061 aluminum alloy were studied by the combined heat treatment process. The microstructure of the specimens after the combination process of deformation and heat treatment was analyzed from metallographic structure, fracture scanning, XRD, transmission electron microscope and so on. Conclusion: (1) the hardness and strength of peak aging of 6061 aluminum alloy after solid solution treatment (540 C, 3H) at aging temperature of 180 and aging time is 4h, and the time of peak aging can not only be increased, but also the greater the shape variable, the higher the hardness and strength, the shorter the time to peak aging, but the more the time, but the time of the peak aging is shorter. When the shape variables are 50%, the final hardness of the specimen without pre aging treatment is 129.6HV, the tensile strength is 368.32MPa, the elongation is 22.10%, the final hardness is 136.7HV, the tensile strength is 385.82MPa, and the elongation is 22.21% before deformation. It can be seen that pre deformation before deformation can not only be seen. It can improve the hardness and strength of the sample, and improve the plasticity of the 6061 aluminum alloy. Under the same total deformation, the final hardness and strength of the sample with peak aging is the highest, but the plasticity is the worst, the middle after recrystallization is the best plastic, but the strength is low, the final hardness of the sample retreated in the middle is the final. The strength and elongation are between the two. (2) the deformation of the solid solution will reduce the conductivity of the 6061 aluminum alloy, and the greater the deformation, the more serious. The electrical conductivity of the 6061 aluminum alloy will increase gradually with the aging time, and the electrical conductivity of the 6061 aluminum alloy can be increased by the recovery and recrystallization, and the electrical conductivity of 6061 aluminum alloy can be improved. The effect of crystallization is greater. (3) the deformation before aging can improve the corrosion resistance of 6061 aluminum alloy, and the greater the amount of deformation, the better the corrosion resistance of the alloy. Under the same deformation quantity, the pre aging of the deformation will reduce the corrosion resistance of the 6061 aluminum alloy after the peak aging; the corrosion resistance of the specimen treated by recovery and recrystallization is better than that of the specimen treated after the deformation. The effect of the recrystallization treatment is more significant. The effect of different intermediate heat treatment on the final corrosion resistance of 6061 aluminum alloy is different. (4) the deformation treatment before aging makes the grain elongate, and the larger the deformation, the more obvious the grain length is, the recrystallization will refine the grain after the deformation; the deformation before aging is not only the shadow. The intensity of the diffraction peak will also offset the position of the diffraction peak, and the heat treatment after deformation only affects the strength of the final diffraction peak of 6061 aluminum alloy, but has little effect on the position of the diffraction peak. (5) the tensile fracture of 6061 aluminum alloy under different deformation and heat treatment process are all ductile fracture, deformation, preaging and intermediate heat. The shape of 6061 aluminum alloy will affect the final fracture morphology of aluminum alloy. The greater the deformation amount before aging, the less the number of dimples at the fracture surface, the shallower of the dimple and the worse the plasticity; the predeformation before the deformation can improve the plasticity after the peak aging of the 6061 aluminum alloy; the grain refinement after the recrystallization, and then the fracture toughness after deformation aging, is toughened. The nests are evenly distributed, the number of large dimples is more and the ductility is deeper and the plasticity is better. (6) the deformation will produce a large number of dislocation, the larger the shape variable, the more serious the dislocation entanglement, the unevenly distributed, the deformation substructure when the deformation amount is 50%, and the deformation substructure is more obvious and the size is more uniform before the deformation of the pretreated sample. After the deformation of the crystal, the dislocation density in the crystal is slightly reduced and the vacancy disappears. After recrystallization, the dislocation basically disappeared, and then the dislocation entangled and the strength of the alloy increased.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.21;TG166.3

【参考文献】