The creep deformation and fracture behaviors of nickel-base superalloy M951G at 900 °C
The creep deformation and fracture behaviors of nickel-base superalloy M951G at 900 °C
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DOI：
10.1016/j.msea.2017.09.066
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发表时间：
2017-11
期刊：
影响因子：
6.4
通讯作者：
Luqing Cui;Huhu Su;Jin-jiang Yu;Jinlai Liu;T. Jin;Xiao-feng Sun
中科院分区：
文献类型：
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作者：
Luqing Cui;Huhu Su;Jin-jiang Yu;Jinlai Liu;T. Jin;Xiao-feng Sun
研究了M951G合金在900℃、240 ~ 400 MPa应力范围内的蠕变行为，并采用多种技术研究了M951G合金断裂后的变形机制和断裂行为。结果表明，变形机制和断裂行为都与外加应力有关。透射电镜观察表明，随着外加应力的增加，主要变形机制由基体通道位错的滑移和爬升联合过程转变为γ′相位错的剪切和基体通道位错的交叉滑移。利用光学显微镜（OM）和扫描电镜（SEM）对M951G合金的断裂行为进行了表征，随着外加应力的增加，断裂行为由沿晶向穿晶转变。在低外加应力下，M951G合金由于晶界微孔的聚并导致沿晶破坏。然而，在较高的外加应力下，微裂纹始于晶粒内部的碳化物断裂，最终导致穿晶断裂。此外，蠕变应变速率通过影响晶界和晶内相应的等强度温度，对蠕变断裂模式的转变也起着关键作用。低应力区和高应力区的表观应力指数分别为5.14和11.13，这是由于随外加应力的增加，变形机制和断裂模式发生了变化。
The creep behaviors of M951G alloy were carried out under stress ranging from 240 MPa to 400 MPa at 900 °C, and the corresponding deformation mechanisms and fracture behaviors after rupture had been investigated by various techniques. Results showed that both the deformation mechanisms and fracture behaviors were dependent on the applied stress. According to the transmission electron microscope (TEM) observations, the dominant deformation mechanism changed from a combined process of slip and climb of dislocations in matrix channel to shearing of dislocations in γ′ precipitates and cross-slip of dislocations in matrix channel with the applied stress increasing. Fracture behaviors of M951G alloy were characterized using optical microscope (OM) and scanning electron microscope (SEM), which changed from intergranular to transgranular with the increase of applied stress. At low applied stress, M951G alloy was failure in the form of intergranular owing to coalescence of micropores along the grain boundaries. However, at higher applied stress the microcracks initiated at broken carbides in the grain interior, and finally resulted in transgranular fracture. Additionally, creep strain rate also played a key role in determining the transition of creep fracture modes by effect the corresponding temperature of equal strength for grain boundary and grain interior. The values of apparent stress exponent at low and high stress regions were calculated to be 5.14 and 11.13 respectively, which was due to the change of deformation mechanisms and fracture modes with the increase of applied stress.