In718晶粒尺寸对超声背散射信号的影响及其无损评价方法  

EFFECTS OF IN718 GRAIN SIZE ON ULTRASONIC BACKSCATTING SIGNALS AND ITS NONDESTRUCTIVE EVALUATION METHOD

作　　者：宋永锋[1] 李雄兵[1,2] 吴海平[1] 司家勇[2] 韩晓芹[1] 

机构地区：[1]中南大学交通运输工程学院,长沙410075 [2]中南大学粉末冶金国家重点实验室,长沙410083

出　　处：《金属学报》2016年第3期378-384,共7页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目61271356和51575541;国家高技术研究发展计划项目2012AA03A514;中央高校基本科研业务费项目2014zzts203;中南大学粉末冶金国家重点实验室基金项目2014M562126资助~~

摘　　要：制备晶粒尺寸不同的In718合金试样,采用经验模态分解(EMD)研究超声背散射信号的时频域特征,分析晶粒尺寸对不同频段固有模态函数(IMF)的影响,并探求各IMF信号的功率与晶粒尺寸之间的相关性.结果表明,原始背散射信号和IMF1信号的频带宽受晶粒尺寸变化影响均不显著;IMF2信号频域分布较为集中,峰值频率的幅值随晶粒的增大而增大,其功率与晶粒尺寸相关系数达0.995,显著高于其它模态,EMD过程实质上滤除了与晶粒尺寸无关的成分.以充分反映晶粒散射强度的IMF2成分作为晶粒尺寸评价的特征信号,建立面向In718晶粒尺寸的超声背散射EMD评价模型.晶粒尺寸实测结果显示,本方法的灵敏度是传统背散射法的3.7倍;对2个验证试样的评价误差分别为-3.72%和2.87%,精度显著高于声速法;与衰减法相比,本方法无需厚度信息,评价结果不受测厚误差的影响;此外,相比于金相法具有效率高及无需破坏待测件的优势.Superalloy In718 enjoys wide application in such crucial parts as turbine engine disks due to high strength, great toughness and corrosion resistance in different temperature environment. Since the mechanical properties of superalloy In718 are greatly influenced by the grain size, a nondestructive detection method is studied in order to determine the grain size quickly and effectively. In this work, superalloy In718 samples of different grain sizes were produced and the empirical mode decomposition（EMD） method was employed to find the characteris-tics of the time- frequency domain of the ultrasonic backscattering signals. Then the effects of the grain size over the intrinsic mode function（IMF） of different frequency bands were analyzed to seek the relations between the grain size and the power of the IMF signals. The original backscattering signals and IMF1（the first IMF） signals barely respond to the change of the grain size because of their wide frequency bandwidths; the distribution of the frequency domain of the IMF2 signals is centralized and the amplitude of the peak frequency increases with the grain size, and the correlation coefficient between the power and the grain size is 0.995, much higher than that of other modes. This method eliminates the components irrelative to the grain size and takes the IMF2 components which fully reflect the intensity of the grain scattering as the characteristic signals of the grain size evaluation to build an ultrasonic backscattering EMD model evaluating the grain size of superalloy In718. The actual measurement results of the grain size show that the sensitivity of this method is 3.7 times over the traditional backscattering method; the evaluation errors over the two verification test samples are-3.72% and 2.87%, apparently more accurate than the ultrasonic velocity method; compared with the attenuation method, this method requires no information of the thickness so that the evaluation results are independent of the thickness measuring error;compared with the

关 键 词：In718高温合金 晶粒尺寸 超声无损评价 背散射信号 经验模态分解 固有模态函数 

分 类 号：TG115.21[金属学及工艺—物理冶金] TG115.28[金属学及工艺—金属学]