Abstract

The existence of long period stacking ordered (LPSO) strengthening phases greatly improves the mechanical properties of Mg alloys, such as tensile strength, compressive strength and ductility. Therefore, volume fraction detection of LPSO phases plays an important role in understanding the properties of the alloy. Aiming at the traditional volume fraction detection of LPSO phases in Mg alloys destroys the tested material, a nondestructive testing method based on acoustic attenuation signal is proposed. In order to improve the sensitivity of the signal to the LPSO phases content, the dual-tree complex wavelet packet transform (DTCWPT) is used to extract the feature frequency band. Regarding Mg alloys with different volume fractions of LPSO phases as the research specimens, the feature frequency bands are extracted by DTCWPT. The fitting equation between the energy attenuation coefficient of the feature frequency band signal and the volume fraction of LPSO phases is established, and is used to calculate the LPSO phases content of the testing specimen. The results show that the proposed method is able to reliably calculate the volume fraction of LPSO phases, the absolute error of the phases volume fraction of testing specimens are 2.5 and 3.1%, which are 1.2 and 0.8% less than the absolute error 3.7 and 3.9% calculated by WPT method, and also 2.3 and 1.6% less than the absolute error 4.8 and 4.7% calculated by the original signal. Therefore, the volume fraction detection method of LPSO phases based on DTCWPT is a better method, which opens up a new nondestructive detection method of volume fraction of LPSO phases in Mg alloys.

中文翻译：

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基于双树复小波包变换的镁合金长周期堆积有序相体积分数检测

摘要

长周期堆积有序（LPSO）强化相的存在大大提高了镁合金的拉伸强度、压缩强度和延展性等力学性能。因此，LPSO 相的体积分数检测在了解合金的性能方面起着重要作用。针对传统镁合金中LPSO相体积分数检测会破坏被测材料的问题，提出了一种基于声衰减信号的无损检测方法。为了提高信号对LPSO相位内容的敏感度，采用双树复小波包变换（DTCWPT）提取特征频带。以不同体积分数的LPSO相镁合金为研究样本，通过DTCWPT提取特征频段。建立特征频带信号能量衰减系数与LPSO相体积分数的拟合方程，用于计算试样的LPSO相含量。结果表明，该方法能够可靠地计算出LPSO相的体积分数，试件相体积分数的绝对误差分别为2.5%和3.1%，比绝对误差3.7和3.9分别小1.2%和0.8%。 WPT方法计算的%，也比原始信号计算的绝对误差4.8%和4.7%小2.3%和1.6%。因此，基于DTCWPT的LPSO相体积分数检测方法是一种较好的方法，开辟了镁合金LPSO相体积分数无损检测的新方法。