单双级时效对7A55铝合金组织及其性能的影响
摘要利用硬度试验、透射电镜、金相显微镜、电导率测试、拉伸试验、剥落腐蚀 实验等研究单/双级时效制度对 7A55 铝合金的组织及其性能的影响。结果表明： 7A55 铝合金的单级时效硬化速率和电导率随时效温度的提高而提高，得到最优 化的单级时效制度为：120℃×24h。经该制度处理后，7A55 铝合金的强韧性和 耐蚀性分别为：抗拉强度 651MPa，屈服强度 583MPa，延伸率 16。8%，剥落腐 蚀等级 EC。7A55 铝合金耐蚀性的提高主要取决于第二级时效制度。第二级时 效温度越高，达到相同性能(电导率和强硬度)所需的时间越短；第二级时效温度 相同，二级时效时间越长，则合金强度越低，但耐蚀性和断裂韧性越高。综合考 虑 7A55 铝合金对强韧性和耐蚀性的要求，得到最优化的双级时效制度为： 120℃×6h+ 160℃×16h。经该制度处理后，7A55 铝合金的强韧性和耐蚀性分别 为：抗拉强度 580MPa，屈服强度 549MPa，延伸率 12%，剥落腐蚀等级 EB。83334
毕业论文关键词：7A55 合金；时效；微观组织；力学性能；腐蚀性能
Abstract The effects of single and double aging on the microstructure and propertie s of 7A55 aluminum alloy were studied by hardness test, transmission electron microscopy, metallurgical microscope, electrical conductivity measurement, tens ile test and corrosion resistance test。 The results showed that, the higher the ag
ing temperature, the higher the hardening rate and electrical conductivity。 The optimized single aging treatment was:120℃×24h。 Under this condition, the tens ile strength, yield strength, elongation and corrosion grade were 652MPa,583M
Pa,16。8% and EC, respectively。 The improvement of corrosion resistance of 7A
55 aluminum alloy mainly depends on the second aging treatment。The higher t he double aging temperature, the shorter the aging time required to achieve the same properties。When the double aging temperature was the same, the longer the aging time, the lower the strength of the alloy, while the higher the corros ion resistance and fracture toughness。 The requirements of strong toughness and corrosion resistance of alloy were comprehensively considered, the optimized
double aging treatment was: 120℃×6h+160℃×16h。 Under this condition,the ten
sile strength,yield strength,elongation and corrosion grade of the studied alloy were 580MPa,549MPa,12% and EB, respectively。
Keywords: 7A55 aluminum alloy; aging; microstructure; mechanical properties; corrosion resistance
目 录
第一章 绪 论 1
1。1 引言 1
1。2 常用 Al-Zn-Mg-Cu 合金简介 3
1。3 7055(7A55)铝合金的应用背景 4
1。5 本文的研究内容 11
第二章 实验材料与方法