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7050铝合金材料淬透性的末端淬火研究
【作者】 张勇;
【导师】 邓运来;
【作者基本信息】 中南大学 , 材料加工工程, 2008, 硕士
【摘要】 7050铝合金是20世纪七十年代,在7075合金基础上通过以Zr代替Cr、Mn和调整Zn、Mg含量研制出的高强铝合金,该合金厚板主要用于现役各种大型飞机的主承力构件。淬透性控制是制备7050合金厚板必须解决的难题,而高强铝合金的淬透性鲜见报道,因此开展7050铝合金厚板材料的淬透性研究不仅可以丰富铝合金淬透性研究的内容,而且能为高性能铝合金厚板的组织、性能均匀性及其淬火残余应力控制技术提供依据。本文设计、制作了一套适合于铝合金材料的末端淬火试验装置,对7050铝合金热轧厚板的淬火过程进行了模拟与试验研究,通过淬透性曲线测试,结合OM、SEM和TEM观察研究了不同冷却特性淬火介质对该合金厚板材料淬透性的影响,得到以下结论:(1)建立了水作为淬火介质时末端淬火试样喷淋表面换热系数与温度的非线性关系,据此用有限元模拟计算末端淬火试样的冷却温度场符合实测温度场,建立了一套测试—数值解析相结合求解末端淬火喷淋表面换热系数与温度场的方法。(2)20℃水,10 wt-%盐水和有机聚合物(PAG)溶液分别作为末端淬火喷淋介质,T6时效处理,7050铝合金热轧厚板材料末端淬火试样硬度下降到HV3=175(约10%)的淬透深度分别约为60mm、60mm和45mm,喷射PAG溶液时淬透性曲稳定性最好。(3)MgZn2平衡相脱溶,晶界、亚晶界的迁移和无沉淀析出带均受淬火冷却速率的控制。MgZn2相脱溶的淬火临界平均冷却速率为40~60℃/s。
【Abstract】 7050 aluminum alloy is an Al-Zn-Mg-Cu-based high strength alloy developed by replacement of dispersoid-forming Cr and Mn with Zr and changing contents of Zn and Mg in the 7075 aluminum alloy in the 1970s. Typical applications for 7050 Al alloy thick plate are fuselage frames and bulkheads in active service large airplanes.It is a key to control penetration as quenching(hereafter hardenability)because of its quench sensitivity.However,there is few literature quantitatively reports the hardenability about 7000 series aluminum alloy.In fact,the quantitative hardenability is very important to maximize magnitude properties and uniformity of microstructures and minimize residual stress in quenched high strength aluminum alloy thick plate.In present paper,a demonstration quenching testing system of Jominy End Quench method adapts to aluminum alloy materials is established. Hardenability of samples cut from a 7050 Al alloy hot-rolled thick plate is investigated by testing the hardenability curves after being quenched by spraying various reagents.The microstructures of different cooling rates are characterized by optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).As a result,the conclusions can be gotten:(1)The demonstration method of non-linear relationship between surface heat-transfer coefficient and temperature of the sample has been established.This non-linear surface heat-transfer coefficient by spraying water at 20℃is used to simulate the temperature-field of the quenched sample.The simulated result is consisted with the measured one.(2)The hardenability curves of the 7050-T6 samples are determined by spraying water,10-wt%brine and PAG regent at 20℃,respectively, the depths corresponding to HV3=175(hardness approximately decrease by 10%)are 60mm,60mm,45mm,respectively.The most stable hardenability curve is contributed by spraying PAG reagent.(3)The precipitation of.(MgZn2)phase,remotion of grain or/and subgrain boundaries,and precipitation free zone(PFZ)are affected by the cooling rates.The critical average cooling rate of precipitating phase is about 40~60℃/S.
【Key words】 7050 aluminum alloy; Thick plate; Quench sensitivity; Hardenability; heat-transfer coefficient; Microstructure;
- 【网络出版投稿人】 中南大学 【网络出版年期】2009年 01期
- 【分类号】TG166.3
- 【被引频次】30
- 【下载频次】931