论文标题:电解含钛铝合金的疲劳性能研究
Study of the Fatigue Property of Electrolytic Titanium-contained Aluminum Alloy
论文作者 徐以锋
论文导师 翁永刚,论文学位 硕士,论文专业 凝聚态物理
论文单位 郑州大学,点击次数 48,论文页数 74页File Size5750k
2003-05-01论文网 http://www.lw23.com/lunwen_373722492/ 电解低钛铝合金;电解铝硅钛合金;晶粒细化;S-N曲线;疲劳门槛值;疲劳裂纹扩展
electrolytic low content titanium alloy;electrolytic Al-Si-Ti alloy;grain-refining;fracture toughness;S-N curve;fatigue threshold;fatigue crack propagation
电解低钛铝合金和电解铝硅钛合金是两种新型工艺生产的铝合金，对以二者和纯铝为基本原料制备的应用铸造合金的力学疲劳性能进行综合的对比研究，将会对客观评价这两种新材料的性能、在工业生产上推广新工艺，具有非常重要的现实意义和参考价值。 文章首先考察了含钛铝合金当前在工业上的发展状况，以及我国在这方面与发达工业国家之间存在的差距，介绍了传统工艺方法生产含钛铝合金的局限性，以及两种新型工艺生产电解含钛铝合金的研究进展情况，强调了材料的疲劳性能在现代工程应用上的重要性。 为研究铝合金中所含钛和电解加钛方式对铝合金疲劳性能的影响，分别利用电解低钛铝合金、电解铝硅钛合金和纯铝制备成三种铝硅系合金中重要的常用铸铝ZL101A和ZL101，测试其疲劳性能以及相关力学性能，并进行对比研究。微观组织分析结果表明，相对于不含钛的ZL101，微量的钛可以使电解低钛铝合金制备的ZL101A(AlTi101A)和电解铝硅钛合金制备的ZL101A(AST101A)的α(Al)相的晶粒细化，晶粒大小分布均匀，但对它们的Si粒子尺寸和形貌影响不大。 以上述三种试验铝合金为对象，首先对比研究了不同的成分和组织对合金拉伸性能和断裂韧性的影响。结果表明，Ti对晶粒的细化可以大幅提高试验合金的抗拉强度、延伸率和断裂韧性，但对合金的屈服强度影响不大。AST101A中微量的Fe元素对合金的弹性模量会有所影响，对合金的抗拉强度和屈服强度影响很小，但会大大降低合金韧性和塑性。 通过高周疲劳测试方法研究了AST101A和AlTi101A抵抗疲劳裂纹萌生的性能，把最大似然法和相关系数法结合起来处理不完全疲劳寿命数据，给出了AST101A的S—N曲线、P—S—N曲线和疲劳极限，讨论了加载历史、缺陷等对疲劳寿命的影响。 对比研究了上述三种合金的化学成分对微观组织结构，及其所引起的材料疲郑州大学硕士论文电解含钦铝合金的疲劳性能研究劳裂纹扩展性能和疲劳门槛值的显著差异。结果表明，AST101A、AITi101A和ZL101中51粒子的浓度、大小和形貌对材料疲劳门槛值的高低有一定的作用，脆性的富Fe相是疲劳门槛值降低的另一个重要原因。随着疲劳裂纹扩展速率从近门槛值区向Paris区过渡，细小的a(A1)晶粒会加速疲劳裂纹的扩展。三种试验合金在Paris区的扩展没有明显的差别，表现出裂纹扩展速率在Paris区时，疲劳裂纹扩展对微观组织结构的不敏感性。但随后的扩展会受富Fe相和si粒子的大小和形貌的共同影响，致使ASTIOIA的扩展速率最大，而AITi101A的最小。 本文较全面地测试和对比研究了以电解低钦铝合金和电解铝硅钦合金这两种新型电解含钦铝合金为原料制备的铸造合金ASTIOIA和AITi1OIA的疲劳性能以及相关力学性能。结果表明，电解低钦铝合金制备的AITi IOIA具有良好的拉伸性能、断裂韧性和抵制裂纹扩展的能力，电解铝硅钦合金中较高含量的Fe降低了AST 1 01A的疲劳性能以及相关的力学性能指标，因此降低电解铝硅钦合金中的铁含量，或使合金中的铁变质将会提高AST101A的疲劳性能和相关力学性能。
Electrolytic low content titanium aluminum alloy and electrolytic Al-Si-Ti alloy are two new alloy materials produced by new technique of production. It"ll have very important practical value and referential significance in evaluating the properties of the two new materials and generalizing the new technique of production in industry to study and compare the fatigue properties and relevant mechanical properties of the applied cast alloys made from them and pure aluminum comprehensively.In this paper, current development of the titanium-contained aluminum alloys in industry and the gap between our country and advanced industrial counties were introduced first. The shortage of traditional technique for producing the titanium-contained aluminum alloy and the current research of the two new titanium-contained aluminum alloys produced in new technique were analyzed in detail. Then the significance of material"s fatigue property in current engineering application was emphasized particularly.In order to study the influence of the existence and adding ways of trace titanium on the fatigue properties of aluminum alloys, three important common-used standard cast alloys ZL101A and ZL101 were prepared with electrolytic low content titanium aluminum alloy, electrolytic Al-Si-Ti alloy and pure aluminum respectively. The fatigue properties and relevant mechanical properties of these three cast alloys were tested and compared comprehensively. The analyses of their microstructure showed that comparing with ZL101 that contained no titanium, the trace amounts of titanium in alloys caused grain refining of Al-l%Si in ZL101A prepared from electrolytic low content titanium aluminum alloy (i.e. AlTi101A) and ZL101A prepared from electrolytic Al-Si-Ti alloy (i.e. AST101A), and the grain size distribution became more even, whereas the trace amounts of titanium have little influence on the size andshape of Si particles in these alloys.This paper studied the influence of different chemical components and microstructure in above aluminum alloys on their tensile properties and fracture toughness. The results showed that the grain refining by the trace amounts of titanium could improve the tensile stress, percentage elongation and fracture toughness, but had little influence on their yield stress. The trace amounts of iron hi AST101A could affect its elastic modulus, but not its tensile stress and yield stress, at the same time decrease its plasticity and fracture toughness notably.The abilities of resisting the incubation of fatigue crack in AST101A and AlTi101A were tested with the high-cycle fatigue method. A method combining the maximum likelihood estimation method with the correlation coefficient method was suggested to analyze the fatigue life experimental data some of which were incomplete. The S-N curve and P-S-N curves were presented, and the influence of the loading history and the defects in specimen on fatigue life was discussed.The remarkable differences of the fatigue crack propagating rates and the fatigue threshold among the above three alurninum alloys were studied and compared, which were caused by the microstructure based on alloys" chemical components. The results showed that the concentration, size and shape of Si particles in AlTilOlA, AST101A and ZL101 had some effects on the fatigue threshold, and the irregular shaped brittle phase of Fe intermetallics caused the fatigue threshold decreased. The fining grains of Al-l%Si could accelerate the fatigue crack propagation from the near threshold zone to Paris zone.The fatigue crack propagating rates of the above aluminum alloys in Paris zone had no remarkable differences. It was showed that fatigue crack propagating rates had little susceptivity to the microstructure of the above alloys in Paris zone. In contrast, the size and shape of Si particles and the phase of Fe intermetallics could affect the fatigue crack propagating rates beyond the Paris zone. The fatigue crack propagating rate of AST101A was the highest, and that of AlTilOlA was the lowest
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