【作者】 宋继晓；

【导师】 戴光泽；

【作者基本信息】 西南交通大学 ， 材料科学与工程， 2011， 硕士

【摘要】 铝合金由于密度小、比强度高、优良的导电性、导热性和抗蚀性以及塑性,因此被广泛应用于航空航天、汽车、机械制造、船舶及化学工业等领域。高强铝合金的性能主要取决于它的基体组织和第二相析出物的分布和形态,而第二相析出物的分布和形态则受固溶和时效热处理工艺制度影响,因此只有采用合适的固溶和时效热处理工艺制度,才能获得具有优异综合性能的高强铝合金。本课题研究针对7A04高强铝合金,采用不同的热处理工艺制度进行了固溶、单级时效、双级时效以及三级时效处理。对不同时效工艺热处理后的试样进行拉伸实验、冲击实验、盐雾实验以及晶间腐蚀实验；采用激光共聚焦金相显微镜、透射电子显微镜对不同固溶时效工艺热处理后的组织进行观察分析。研究结果表明,较合理的固溶热处理工艺制度是470℃时固溶1小时,该固溶工艺制度可以较好控制第二相的回溶数量,获得较好晶粒匹配度；试样经三级时效处理后,基体组织中析出细小弥散分布的第二相,具有最优的的综合机械性能,抗拉强度达到642 MPa,屈服强度达到546MPa,延伸率高达13.5%,冲击功提高到14J；拟合抗拉强度和硬度的线性回归方程为：Yi=100.742+2.919Xi,该方程较好反映了7A04高强铝合金抗拉强度和硬度的对应关系；晶间腐蚀试验表明,不同时效工艺处理的7A04铝合金没有明显的晶间腐蚀现象,但是双级时效和三级时效处理的铝合金晶间腐蚀倾向更低；盐雾腐蚀试验结果表明,三级时效处理的铝合金抗盐雾腐蚀性能较好,双级时效处理的铝合金抗盐雾腐蚀性能次之,单级时效处理的铝合金抗盐雾腐蚀性能较差。通过上述对7A04高强铝合金固溶、时效热处理工艺制度的研究,优化出7A04高强铝合金的最佳热处理工艺制度。更多还原

【Abstract】 Aluminum alloy was widely used in aerospace aircraft, automotive, machinery manufacturing, chemical industry and vessel because of its low density, high specific strength, excellent conductivity and thermal conductivity, high corrosion resistance and good plasticity. The properties of the ultra-high strength aluminum alloy are due to its matrix microstructures and morphology and distributions of the second-phase precipitates affected by solution and ageing treatment. In order to obtain the excellent mechanical properties, it must be took the suitable solution-ageing treatment.In this paper, the mechanical properties of the ultra-high strength 7A04 aluminum alloy at different heat-treatment conditions, including solution, single-ageing, two-stage aging and three-stage aging, were investigated by room temperature tensile test, hardness and impact toughness test, neutral salt spray test and intergranular corrosion test. The microstructures were investigated by optical microcopy, laser confocal scanning microscope and transparent electron microscope. The results show that the optimal solution treatment is treated at 470℃for 1 hour. The amount of coarse second phases can be reduced effectively and the size of grain can be controlled. The mechanical properties of aluminum alloy can be greatly improved. The dispersive distribution of the second phases can be abtained by using three-stage aging treatment which has the best mechanical properties. At this condition, tensile strength, yield strength, elongation and impact toughness respectively reach 642MPa, 546MPa,13.5%, and 14J. It has been deduced the linear regression equation which could reflects the corresponding relationship between tensile strength and hardness: Yi=100.742+2.919Xi. Aluminum alloy treated by three-stage aging treatment can obtain the best resistance againt salt spray and intergranular corrosion, and aluminum alloy treated by single-ageing treatment the single-ageing treatment obtain the worst resistance againt salt spray and intergranular corrosion.After the results were analyzed and discussed theoretically, the heat-treatment processes were optimized.更多还原