Al-Cu-Mg合金疲劳性能与热稳定性的研究

【作者】 周杰；

【导师】 刘志义；

【作者基本信息】 中南大学 ， 材料学， 2008， 硕士

【摘要】 2524合金属于Al-Cu-Mg系的高强度低比重变形铝合金,在航空、航天部门和其它军工品上应用十分广泛。本课题利用室温常规力学拉伸、热暴露、疲劳裂纹扩展速率测定、透射电镜、高分辨透射电镜、3DAP分析、DSC分析和扫描电镜等测试、分析方法研究了高温短时人工时效、微合金化对Al-Cu-Mg合金的室温力学性能、疲劳性能、热稳定性能、微观组织结构及其变化规律的影响。本实验采用了高分辨透射电镜以及3DAP分析等先进的检测方法,对高温短时人工时效后的2524合金疲劳性能、热稳定性能以及疲劳裂纹尖端循环应力对疲劳裂纹扩展速率的影响进行了研究。实验结果表明:高温短时时效态的2524合金基体中的GPB区尺寸大于T351态的2524合金,且高温短时人工时效可以延缓2524合金在热环境下的组织退化,提高疲劳裂纹扩展阻力,高温短时人工时效获得的合金组织在疲劳裂纹扩展过程中更难发生回溶,并可以有效地阻止应力循环软化的发生,提高了合金疲劳性能。在2524合金中添加微量的Ag,对于不同的初始热处理状态,Ag的作用不同。虽然自然时效和人工时效态的合金中均没有明显的析出相析出,但是合金基体中原子的偏聚状态却是不一样的,这就造成了在后续热暴露过程中合金组织变化的不同。通过改变2524+Ag合金中Cu的含量以及调整Cu/Mg比均有利于合金力学性能及热稳定性的提高。Cu含量降低的0701合金无论是时效态还是热暴露后的力学性能均比2524+Ag合金的性能高,而调整了Cu/Mg比后的0626合金的强度在三个合金中无论是时效态还是热暴露后始终保持最大。更多还原

【Abstract】 Al-Cu-Mg alloys have many excellent performances,such as high strength,high elastic modulus.They are widely used in space flight and aviation as new structural materials.The effects of high temperature-short time aging treatment and micro-alloying on the room mechanical properties、fatigue crack propagation、thermal stability and microstructure evolution have been investigated.The modern analysis(HRTEM and 3DAP analysis)techniques were used to investigate the fatigue crack propagation、thermal stability of high temperature-short time aged 2524 aluminum alloy and the effect of the cyclic stress located in the fatigue tip on the fatigue crack growth rate. The results are:The hardening microstructure-GPB zones size of 2524 aluminum alloy are obtained by high temperature-short time artificial aging treatment(170℃/30min)is lager than that by natural aging treatment.The high temperature-short time artificial aging treatment can restrain the degradation of GPB zones.The fatigue crack growth of high temperature-short time artificial aged samples was decreased.The larger GPB zones obtained by artificial treatment are hard to redissolve,that retard the cyclic softening effect in the alloy.Further more,the fatigue crack propagation resistance is enhanced.Ag has played different roles in the mechanical properties of 2524 aluminum alloy with trace addition of Ag.In the nature aged and artificial aged alloys,there are no distinct precipitates in the matrix,but there are different precipitations in the matrix after thermal exposure treatments because of different solute clusters obtained after different aging treatment.It can enhance the mechanical properties and thermal stabilities of 2524+Ag alloy by changing the Cu content and Cu/Mg ratio.The properties of 0701 alloy which has a lower Cu content are higher than that of 2524+Ag alloy no matter under what heat treated and whether thermal exposed.Even more,the properties of 0626 alloy has a higher Cu/Mg ratio is the best in the three of alloys.更多还原