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首页> 外文会议>CORROSION Annual Conference and Exposition >UTILIZATION OF LOW TEMPERATURE RETROGRESSION AND RE-AGING (RRA) HEAT TREATMENTS TO IMPROVE STRENGTH/SCC PROPERTIES FOR THICK SECTION COMPONENTS OF ALUMINUM ALLOY 7075 FOR AGING AIRCRAFT REFURBISHMENT
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UTILIZATION OF LOW TEMPERATURE RETROGRESSION AND RE-AGING (RRA) HEAT TREATMENTS TO IMPROVE STRENGTH/SCC PROPERTIES FOR THICK SECTION COMPONENTS OF ALUMINUM ALLOY 7075 FOR AGING AIRCRAFT REFURBISHMENT

机译：低温倒置和再老化（RRA）热处理的利用率改善铝合金7075厚截面部件的强度/ SCC性能，用于老化飞机翻新

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Aluminum alloy 7075, a common material in the aerospace industry, is susceptible to intergranular stress-corrosion cracking (SCC) in the T6, or peak-aged temper. The susceptibility of this temper to SCC is alleviated through the use of the T73, or overaged temper that provides SCC resistance, but at a 10-15% strength loss compared to the T6 temper. Experimental test results by Cina and Ranish indicated that retrogress and re-aging (RRA) heat treatments with retrogression performed at 200-280°C for less than 10 minutes reduce the traditional trade-off between T6 strength and T73 SCC resistance. However, the short time heat treatment limited the applicability of RRA to thin sections of material. The primary goal of this effort was to determine if lower retrogression temperatures could be used in the RRA process to extend the applicability of this heat treatment to thick section aircraft components. Tensile, fatigue, fracture toughness, and hardness tests were conducted to characterize the mechanical properties of T6, T73, and various RRA tempers. Alternate immersion (AI) and double-cantilever beam (DCB) tests were conducted to evaluate the SCC resistance of the different tempers. Results verified that the T6 temper exhibits strengths that are ten to fifteen percent higher than the T73 temper, but has crack growth rates that are approximately ten times faster than T73. Furthermore, the T6 temper failed via environmental cracking much more quickly when subjected to 3.5% NaCl in the alternate immersion test. Improvements in properties were demonstrated using RRA heat treatments at lower temperatures and longer times than those previously investigated. In general, the various RRA tempers below 200°C produced strengths similar to that of T6 with lower crack growth rates. The RRA temper with retrogression at 160°C for 660 minutes produced the greatest improvement, with only a 4% reduction in strength below T6. Stress corrosion crack growth rates for the RRA were significantly lower than that of the T6 temper during the double-cantilever beam experiments and times to failure were substantially longer than T6 in the alternate immersion tests. Additionally, heat transfer analysis indicated the RRA tempers with lower retrogression temperatures and longer retrogression times are more viable for use in industry for thick section components.
机译：铝合金7075是航空航天工业中常见的材料，易于在T6中的晶间应力腐蚀裂纹（SCC），或峰值老化。通过使用T73或提供SCC抗性的过度的脾气来缓解该发脾气对SCC的敏感性，但与T6脾气相比，在10-15％的强度损失下。 Cina和Ranish的实验测试结果表明，在200-280°C的倒退中进行了逆级和再衰老（RRA）热处理，少于10分钟，降低了T6强度和T73 SCC电阻之间的传统权衡。然而，短时间热处理限制了RRA对材料薄切片的适用性。这项努力的主要目标是确定是否可以在RRA过程中使用较低的倒退温度，以将该热处理的适用性扩展到厚截面飞机组分。进行拉伸，疲劳，断裂韧性和硬度试验，以表征T6，T73和各种RRA趋势的机械性能。进行替代浸泡（AI）和双悬臂梁（DCB）测试以评估不同趋吐器的SCC电阻。结果证实，T6脾气表现出比T73脾气高的10至15％，但具有比T73快大约十倍的裂缝增长率。此外，当在交替浸渍试验中受到3.5％NaCl时，T6脾气通过环境开裂更快地失效。使用Rra热处理在较低温度下和比先前研究的时间更长的时间来证明性质的改善。通常，在200℃以下的各种RRA趋势产生与具有较低裂纹生长速率的T6类似的强度。 RA调味在160°C下倒置660分钟，产生了最大的改善，低于T6的强度降低4％。在双悬臂梁实验期间，RRA的应力腐蚀裂纹扩展速率显着低于T6调味的速率，并且在交替浸渍试验中，失效的时间基本上长于T6。此外，传热分析表明RRA抑制器具有较低的倒置温度，并且较长的倒置时间对于工业供工业使用更加可行的厚度部分。

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