基于热机械疲劳试验,建立IN718高温合金感应加热过程中电磁场和温度场耦合的数学模型,对试样在循环加热条件下的非稳态温度场进行仿真,采用电子背散射衍射技术对试样上的晶粒尺寸进行检测并对其数据进行统计分析.结果表明:综合传热系数和风机电压呈正相关的关系;试样径向上存在温度梯度且随时间变化,最大温差为5℃左右,符合试验要求;低周疲劳试样径向上不同点的平均晶粒尺寸均有所增长,且增长幅度基本相同;由于温度梯度的影响,热机械疲劳试样径向上的晶粒尺寸分布不均匀,中心位置和表面位置的平均晶粒尺寸增长幅度分别为16.94%和5.3%.
A mathematic model describing the induction heating process of IN718 superalloy was developed by coupling the electromagnetic field with the temperature based on the thermomechanical fatigue (TMF) test. The transient temperature fields of the specimen under cyclic heating condition were simulated. After the fatigue test, the grain size of the specimen was measured by electron backscattered diffractometry and the data were analyzed. The results indicate that the comprehensive heat transfer coefficient increases with the increase of the fan voltage. The temperature gradient in the radial direction of the specimen changes with time and the maximum of temperature difference is about 5℃, which meets the requirements of the test standard of TMF. The grain sizes of specimen in the radial direction increase at almost the same rate after the low cycle fatigue test. However, the grain sizes of specimen in the radial direction distribute unevenly after the thermomechanical fatigue test, meanwhile the average grain size at the center and the surface increases by 16.94% and 5.3%, respectively.
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