Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy René N4: Part II. Low cycle fatigue behavior
Orientation and temperature dependence of some mechanical properties of the single-crystal nickel-base superalloy René N4: Part II. Low cycle fatigue behavior
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DOI：
10.1007/bf02643956
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
T. Gabb;J. Gayda;R. Miner
中科院分区：
文献类型：
--
作者：
T. Gabb;J. Gayda;R. Miner
研究了单晶镍基高温合金René* N4在760 ° C和980 °C空气中的低周疲劳（LCF）性能。在0.1 Hz的频率下，在完全反向、总应变控制的LCF测试中，对晶体学取向接近[001]、[01 l]、[111]、[023]、[236]和[145]的样本进行测试。在760 °C下，该合金表现出屈服的取向依赖性拉伸-压缩各向异性，其继续失效。此外，在760 °C下，主要表现为单滑移的方向在许多循环中表现出锯齿状屈服。在980 °C下，屈服行为的取向依赖性较小。尽管拉伸-压缩各向异性，循环应力范围-应变范围的行为是没有强烈的取向依赖于任一测试温度。在760 ° C和980 °C下，基于总应变范围的疲劳寿命高度依赖于取向，并且主要与弹性模量相关，低模量取向具有更长的寿命。在760 °C时，（111）平面上的第I阶段裂纹扩展占主导地位，而第II阶段裂纹扩展发生在980 °C。裂纹萌生通常发生在近表面微孔处，但偶尔发生在980 °C试验中的氧化峰值处。
The low cycle fatigue (LCF) properties of a single-crystal nickel-base superalloy, René* N4, have been examined at 760 and 980 °C in air. Specimens having crystallographic orientations near [001], [01l], [111], [023], [236], and [145] were tested in fully reversed, total-strain-controlled LCF tests at a frequency of 0.1 Hz. At 760 °C, this alloy exhibited orientation dependent tension-compression anisotropies of yielding which continued to failure. Also at 760 °C, orientations exhibiting predominately single slip exhibited serrated yielding for many cycles. At 980 °C, orientation dependencies of yielding behavior were smaller. In spite of the tension-compression anisotropies, cyclic stress range-strain range behavior was not strongly orientation dependent for either test temperature. Fatigue life on a total strain range basis was highly orientation dependent at both 760 and 980 °C and was related chiefly to elastic modulus, low modulus orientations having longer lives. Stage I crack growth on (111) planes was dominant at 760 °C, while Stage II crack growth occurred at 980 °C. Crack initiation generally occurred at near-surface micropores, but occasionally at oxidation spikes in the 980 °C tests.