Mg-10Gd-3Y-xNd-0.5Zr耐热镁合金组织与性能的研究

发布时间：2018-04-10 13:33

  本文选题：Nd + 镁合金　； 参考：《河南科技大学》2017年硕士论文

【摘要】：镁-稀土系(Mg-RE)合金具有良好的室温和高温力学性及优异的抗蠕变性能,广泛应用于汽车和航空航天工业中。近年来关于Mg-Gd-Y-Zr系耐热镁合金的研究日益增多,但其力学性能还有进一步提升的潜力。本文以Mg-10Gd-3Y-0.5Zr合金为基础,加入不同含量(0、1wt.%、2wt.%、3wt.%、4wt.%)的Nd,研究Nd对合金显微组织和力学性能的影响。研究结果表明:铸态Mg-10Gd-3Y-0.5Zr合金组织由α-Mg基体和Mg5(Gd,Y)相组成,添加Nd后出现了新相Mg41Nd5。加入适量Nd能改善合金组织,提高合金强度,当Nd添加量为2%时,合金的抗拉强度和屈服强度达到最大值,分别为216MPa、209MPa,此时伸长率为2.6%。铸态Mg-10Gd-3Y-2Nd-0.5Zr合金经固溶535℃×6h处理后,晶界上绝大部分析出相溶入基体,然后在225℃时效,随着时效时间的增加,合金的布氏硬度值先增大后减小,在14h处达到峰值,因此最佳热处理工艺确定为:固溶:535℃×6h;时效:225℃×14h。Nd的适量添加使时效态Mg-10Gd-3Y-xNd-0.5Zr系合金的低温(室温~200℃)力学性能略有降低,但提高了合金的高温(250~350℃)力学性能。随着Nd含量的增加,合金高温耐热性能逐渐升高;同种成分合金随拉伸温度的升高,抗拉强度和屈服强度先增大后减小,出现了强度反常温度效应。伸长率随Nd含量增多逐渐减小,随拉伸温度的升高逐渐增大。时效态Mg-10Gd3Y-xNd-0.5Zr系合金主要强化相为β"相、β'相及具有18R结构的长周期有序结构(LPSO)相。时效态Mg-10Gd-3Y-xNd-0.5Zr系合金具有优异的室温及高温力学性能。Mg-10Gd-3Y-2Nd-0.5Zr合金在200~300℃范围下抗拉强度保持在280MPa以上,250℃为309.5MPa,特别是350℃拉伸时合金抗拉强度仍高达195MPa,表现出优异的耐高温性能,远超商用耐热镁合金WE54。时效态Mg-10Gd-3Y-2Nd-0.5Zr合金在(200℃、250℃、300℃)/(50MPa、70MPa、90MPa)下具有优异的高温抗蠕变性能,明显优于商用耐热镁合金WE54。250℃蠕变后β'相转变成β相,300℃蠕变后β相明显长大。随着蠕变温度和应力的升高,蠕变控制机制由扩散及晶界滑动机制逐渐向位错滑移、位错攀移机制转变。
[Abstract]:Mg-RE-based magnesium-rare earth alloys have good mechanical properties at room and high temperatures and excellent creep resistance. They are widely used in automotive and aerospace industries.In recent years, the research of Mg-Gd-Y-Zr series heat resistant magnesium alloy is increasing day by day, but its mechanical properties still have the potential to improve further.Based on Mg-10Gd-3Y-0.5Zr alloy, the effect of ND on microstructure and mechanical properties of the alloy was studied by adding Nds with different content of 01wt. and 2wt.and 3wt.and 4wt.k.). The effect of ND on the microstructure and mechanical properties of the alloy was studied.The results show that the microstructure of as-cast Mg-10Gd-3Y-0.5Zr alloy is composed of 伪 -Mg matrix and Mg5 + GdGdY) phase, and a new phase Mg41Nd5 appears after addition of ND.The addition of proper amount of ND can improve the microstructure and strength of the alloy. When ND addition is 2, the tensile strength and yield strength of the alloy reach the maximum value, which is 216MPa and 209MPa, respectively, and the elongation of the alloy is 2.6%.After treated with solid solution at 535 鈩，

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