掺杂La-TZM合金板材制备及其高温性能的研究

发布时间：2018-03-28 15:04

  本文选题：TZM合金板材　切入点：粉末冶金　出处：《西安建筑科技大学》2016年硕士论文

【摘要】：TZM(0.4%~0.55%Ti,0.06%~0.12%Zr,0.01%~0.04%C,余量为Mo)合金同时具有高熔点、高强度、强抗腐蚀性能和良好的高温性能,是目前应用最为广泛的钼合金之一。本文利用粉末冶金法制备了TZM及掺杂稀土元素镧的La-TZM合金板材,La以硝酸镧或La2O3粉末形式加入,C元素以硬脂酸的形式加入。通过金相观察合金烧结坯与板材的组织,用Gleeble-3800热模拟实验机对合金烧结坯进行热模拟实验,应变速率分别为0.1s-1和0.01s-1,用高温万能拉伸机对合金板材进行高温拉伸实验,用维氏硬度仪进行了硬度测试,用SEM观察微观组织及断口形貌。主要的研究结果如下:掺杂稀土元素La可以细化TZM合金的组织结构,起到第二相细晶强化的作用,液体掺杂硝酸镧的TZM合金晶粒比固体掺杂氧化镧的TZM合金晶粒小。在0.1 s-1和0.01s-1的应变速率下,变形量为50%时,La-TZM合金的抗压强度均随着温度的升高而降低,且其应力-应变曲线均为单峰值流变曲线,经过压缩,组织为纤维状,未出现再结晶,说明试样并未发生软化现象,其开始再结晶温度高于1200℃。在压缩过程中,由于热传导和变形程度不均导致硬度存在明显差异,变形中心区(区域Ⅲ)维氏硬度最高,未变形区(区域Ⅱ)次之,变形区边缘(区域Ⅰ)最低。La2O3-TZM和La(NO3)3-TZM合金板材的高温抗拉强度、高温屈服强度及维氏硬度均随着温度的升高而降低,而La(NO3)3-TZM合金的高温抗拉强度下降速率更快,即La(NO3)3-TZM合金温度敏感性较高。轧制态合金板材随温度升高,材料韧性先升高后降低,1200℃时达到最大值。当温度小于1400℃时,La2O3-TZM与La(NO3)3-TZM合金板材的高温断裂方式主要为穿晶断裂,当温度大于1400℃时,La2O3-TZM与La(NO3)3-TZM合金板材的断裂方式主要为沿晶断裂,故两种La-TZM合金板材的断裂方式在1400℃左右时由穿晶断裂转变为沿晶断裂,即晶粒与晶界的等强温度为1400℃。
[Abstract]:TZM0. 4 and 0. 55 Ti0. 06 and 0. 12. 12. The alloy has a high melting point, high strength, strong corrosion resistance and good high temperature properties, including 0.04C, with a margin of 0. 04C. It is one of the most widely used molybdenum alloys at present. In this paper, TZM and La-TZM alloy sheet doped with rare earth lanthanum were prepared by powder metallurgy method, and La was added in the form of lanthanum nitrate or La2O3 powder to add C element in the form of stearic acid. The microstructure of sintered billet and sheet metal was observed by metallography. The thermal simulation experiment of alloy sintered billet was carried out with Gleeble-3800 thermal simulation machine, the strain rates were 0.1s-1 and 0.01s-1.The high temperature tensile test of alloy sheet was carried out with high temperature universal drawing machine, and the hardness was tested by Vickers hardness tester. The microstructure and fracture morphology of TZM alloy were observed by SEM. The main results are as follows: doped rare earth element La can refine the microstructure of TZM alloy and play the role of second phase fine crystal strengthening. The grain size of TZM alloy doped with liquid lanthanum nitrate is smaller than that of TZM alloy doped with solid lanthanum oxide. At the strain rate of 0.1 s ~ (-1) and 0.01s-1, the compressive strength of La-TZM alloy decreases with the increase of temperature. The stress-strain curves are all single peak rheological curves. After compression, the microstructure is fibrous, and there is no recrystallization. It shows that the sample does not soften, and the recrystallization temperature is higher than 1200 鈩，

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