固溶时效工艺对Mg-7Y-1Nd合金组织和耐蚀性能的影响
发布时间：2018-11-12 12:06
【摘要】：镁合金轻量化的特点使其在结构材料、功能材料和生物材料等方面具有巨大的应用前景,被成为二十一世纪最有发展空间的"绿色工程材料",然而耐蚀性差却使得其优异的性能难以充分发挥出来。合金化和热处理,可以有效提高镁合金的高温性能和耐蚀性能,是解决镁合金应用瓶颈的有效方法。试验材料为自制WE系列Mg-7Y-1Nd合金,选用热处理方法,优化工艺参数,旨在提高Mg-7Y-1Nd合金的耐蚀性能。论文主要通过浸泡失重试验和极化曲线测试、电化学阻抗谱分析等电化学方法,并辅以合金表面形貌分析、成分分析、物相分析等手段,研究了固溶处理(T4)和固溶+时效处理(T6)对Mg-7Y-1Nd合金耐蚀性能的影响。试验结果表明铸态Mg-7Y-1Nd合金中组织中有不规则骨骼状相沿晶界分布,颗粒状相在晶内分布。固溶温度535℃比515℃的第二相溶解得更彻底,当固溶工艺参数为535℃×12h时,Mg-7Y-1Nd合金的固溶效果最好。当固溶温度为535℃时,随着固溶时间的延长,晶界处不规则骨骼状相逐渐溶入基体。铸态和固溶态中第二相主要有Mg24Y5和Mg41Nd5,颗粒状相主要为富Y化合物,骨骼状相主要为富Nd化合物。时效态Mg-7Y-1Nd合金组织中析出相有Mg24Y5、Mg41Nd5和少量Mg12Nd,其形态有方形颗粒状、棒状、针状及骨骼状相。时效温度越高,时效态Mg-7Y-1Nd合金中颗粒相越粗大,且较易出现聚集长大现象;时效时间的延长,使稀土的扩散越充分,第二相颗粒分布越弥散,但时效时间过长会引起第二相聚集长大,对合金综合性能造成不良影响。最终确定时效温度225℃,时间14 h左右,T6态Mg-7Y-1Nd合金组织最为细致,第二相颗粒细小且弥散分布。研究发现固溶温度为535℃的固溶处理可以有效改善铸态Mg-7Y-1Nd合金在3.5%NaCl溶液中的耐蚀性能。随着固溶时间的延长,Mg-7Y-1Nd合金的耐蚀性呈现先提高后降低的趋势。固溶处理后Mg-7Y-1Nd合金的开路电位稳定在-1.66V左右。时效温度和时间T6态Mg-7Y-1Nd合金的耐蚀性均有影响。根据耐蚀性确定Mg-7Y-1Nd合金最佳热处理工艺参数为:535℃×12h+225℃×14 h。铸态Mg-7Y-1Nd合金的腐蚀失重速率、腐蚀电流密度和平衡电位分别为0.080 g·cm-2·d-1、1.0732×10-3 A·cm-2、-1.7526 V,采用最佳热处理参数处理后Mg-7Y-1Nd合金的腐蚀失重速率、腐蚀电流密度和平衡电位分别为0.0122 g·cm-2·d-1、2.8018×10-4A·cm-2、-1.6382 V。通过电化学阻抗谱及腐蚀形貌分析,分别建立了 T4态和T6态Mg-7Y-1Nd合金腐蚀原理图,固溶态合金的腐蚀类型主要为点蚀,时效态合金腐蚀的主要类型为点蚀和电偶腐蚀。固溶态Mg-7Y-1Nd合金的腐蚀产物由Mg(OH)2、MgO组成,而时效态合金腐蚀产物中出现了Mg41Nd5和Mg24Y5相。
[Abstract]:Due to its lightweight characteristics, magnesium alloys have great application prospects in structural materials, functional materials and biomaterials, and have become the most promising "green engineering materials" in the 21 century. However, the poor corrosion resistance makes it difficult to give full play to its excellent performance. Alloying and heat treatment can effectively improve the high temperature and corrosion resistance of magnesium alloy, and it is an effective method to solve the bottleneck of magnesium alloy application. The test material is WE series Mg-7Y-1Nd alloy. The corrosion resistance of Mg-7Y-1Nd alloy is improved by selecting heat treatment method and optimizing process parameters. In this paper, immersion weightlessness test, polarization curve test, electrochemical impedance spectroscopy and other electrochemical methods were used to analyze the surface morphology of the alloy, composition analysis, phase analysis and so on. The effects of solution treatment (T 4) and solution aging treatment (T 6) on the corrosion resistance of Mg-7Y-1Nd alloy were studied. The results show that there are irregular skeletal phases in the microstructure of as-cast Mg-7Y-1Nd alloys along the grain boundaries and granular phases in the grains. The solution temperature of 535 鈩，
本文编号：2327061
[Abstract]:Due to its lightweight characteristics, magnesium alloys have great application prospects in structural materials, functional materials and biomaterials, and have become the most promising "green engineering materials" in the 21 century. However, the poor corrosion resistance makes it difficult to give full play to its excellent performance. Alloying and heat treatment can effectively improve the high temperature and corrosion resistance of magnesium alloy, and it is an effective method to solve the bottleneck of magnesium alloy application. The test material is WE series Mg-7Y-1Nd alloy. The corrosion resistance of Mg-7Y-1Nd alloy is improved by selecting heat treatment method and optimizing process parameters. In this paper, immersion weightlessness test, polarization curve test, electrochemical impedance spectroscopy and other electrochemical methods were used to analyze the surface morphology of the alloy, composition analysis, phase analysis and so on. The effects of solution treatment (T 4) and solution aging treatment (T 6) on the corrosion resistance of Mg-7Y-1Nd alloy were studied. The results show that there are irregular skeletal phases in the microstructure of as-cast Mg-7Y-1Nd alloys along the grain boundaries and granular phases in the grains. The solution temperature of 535 鈩，
本文编号：2327061
本文链接：https://www.wllwen.com/kejilunwen/jiagonggongyi/2327061.html
