NiAl-28Cr-6Mo共晶合金组织热稳定性研究
发布时间：2018-08-02 12:36
【摘要】：在众多NiAl基高温合金材料中,NiAl-28Cr-6Mo共晶合金的综合性能最佳,但其高温强度不足和高温组织热稳定性差等缺陷,仍制约着该合金的发展和应用。因此,本文采用真空感应熔炼制备出NiAl-28Cr-6Mo(at.%)母合金,并通过定向凝固制备出不同抽拉速率(2.5-160 μm/s)的该合金,研究其组织热稳定性的变化规律和失稳机制,结论如下:在2.5-10μm/s的低速率下,合金的固液界面形貌为平界面,横截面组织为平行相间的黑色NiAl相和灰白色Cr(Mo)相构成;在15-160μm/s的高速率下,合金固液界面形貌为胞界面或带有二次枝的枝界面,横截面组织为大小不一的共晶胞。通过对合金层片间距的测量,结果发现随着抽拉速率的增大,合金组织中的层片间距逐渐减小,且抽拉速率同层片间距近似呈反比例关系。通过对不同层片间距的NiAl-28Cr-6Mo共晶合金进行1150℃的高温热处理,研究了层片间距对该合金的组织热稳定性的影响。结果发现该合金在抽拉速率为2.5 μm/s,层片间距为3.69 μm时,组织热稳定性较好;当抽拉速率增至160 μm/s时,层片间距为0.57μm,合金在高温热处理后组织完全失稳。在浅腐蚀下组织失稳主要呈现为层片夹断和球化,经进一步的深腐蚀研究发现,合金组织失稳的真实情况是层片局部溶解和圆柱化。并得出该合金的组织失稳机制为:终端迁移机制、粗化长大机制和圆柱化机制。通过对不同层片间距的NiAl-28Cr-6Mo共晶合金进行900-1100℃的高温热处理,研究了温度对该合金组织热稳定性的影响。结果发现在平界面速率下(2.5-7.5μm/s),温度对该合金组织热稳定性影响不大,组织中仅发生少量局部溶解,合金组织发生变化是由终端迁移机制控制的;在胞界面速率下(15-160μm/s),温度对该合金组织热稳定性影响显著,随着热处理温度的升高,组织逐渐粗化,甚至圆柱化,导致胞界面速率下合金组织发生显著变化是由于终端迁移机制、颗粒长大机制和圆柱化机制的共同作用。因此,通过本文的研究,得到影响定向凝固制备的NiAl-28Cr-6Mo层片共晶合金的组织热稳定的主要因素为层片间距和温度。随着抽拉速率的增大,层片间距的减小,该合金的组织热稳定降低;随着热处理温度的增加,该合金的组织热稳定性显著降低。
[Abstract]:The comprehensive properties of NiAl-28Cr-6Mo eutectic alloy are the best among many NiAl based superalloy materials, but the defects such as insufficient high temperature strength and poor thermal stability of high temperature structure still restrict the development and application of the alloy. In this paper, NiAl-28Cr-6Mo (at.%) master alloy was prepared by vacuum induction melting, and different drawing rates (2.5-160 渭 m / s) were prepared by directional solidification. The changes of thermal stability and the mechanism of instability of the alloy were studied. The conclusions are as follows: at the low rate of 2.5-10 渭 m / s, The morphology of the solid-liquid interface of the alloy is flat, the cross section of the alloy is composed of black NiAl phase and gray-white Cr (Mo) phase with parallel phase, and at a high rate of 15-160 渭 m / s, the morphology of the solid-liquid interface of the alloy is a cellular interface or a branch interface with secondary branches. The cross section structure is a eutectic cell of different size. By measuring the interlamellar spacing of the alloy, it is found that with the increase of the drawing rate, the lamellar spacing in the alloy structure decreases gradually, and the pulling rate is approximately inversely proportional to the lamellar spacing. The effect of interlaminar spacing on the microstructure thermal stability of NiAl-28Cr-6Mo eutectic alloy with different interlamellar spacing was investigated by high temperature heat treatment at 1150 鈩，
本文编号：2159457
[Abstract]:The comprehensive properties of NiAl-28Cr-6Mo eutectic alloy are the best among many NiAl based superalloy materials, but the defects such as insufficient high temperature strength and poor thermal stability of high temperature structure still restrict the development and application of the alloy. In this paper, NiAl-28Cr-6Mo (at.%) master alloy was prepared by vacuum induction melting, and different drawing rates (2.5-160 渭 m / s) were prepared by directional solidification. The changes of thermal stability and the mechanism of instability of the alloy were studied. The conclusions are as follows: at the low rate of 2.5-10 渭 m / s, The morphology of the solid-liquid interface of the alloy is flat, the cross section of the alloy is composed of black NiAl phase and gray-white Cr (Mo) phase with parallel phase, and at a high rate of 15-160 渭 m / s, the morphology of the solid-liquid interface of the alloy is a cellular interface or a branch interface with secondary branches. The cross section structure is a eutectic cell of different size. By measuring the interlamellar spacing of the alloy, it is found that with the increase of the drawing rate, the lamellar spacing in the alloy structure decreases gradually, and the pulling rate is approximately inversely proportional to the lamellar spacing. The effect of interlaminar spacing on the microstructure thermal stability of NiAl-28Cr-6Mo eutectic alloy with different interlamellar spacing was investigated by high temperature heat treatment at 1150 鈩，
本文编号：2159457
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