Visualization of Solidification Process of Metals by Super High Temperature Electromagnetic Acoustic Transducer Array

了解金属凝固过程是提高金属加工可靠性的关键问题，因此对高温下金属凝固过程监测的传感器有很高的需求。EMAT（电磁声换能器）提供非接触式测量，适用于高温下的测量。限制EMAT工作温度的主要因素是铁轭的居里温度。在这项研究中，我们提出了采用空心线圈作为EMAT的偏置磁源。用EMAT测量了铝合金试样在高温下的脉冲回波波形，并计算了各温度下试样的横波速度。反向回波信号可以在温度范围从RT到400℃进行识别。

Understanding of the metal solidification is a key issue to increase the reliability of the metal processing, and the sensors for monitoring such process at high temperature is highly required. EMAT (Electromagnetic Acoustic Transducer) provides non-contact measurements, and it is suitable for measurements in high temperature. The main factor to limit working temperature of this EMAT is the Curie temperature of iron yoke. In this study we proposes to use air-cored coil as the bias magnetic source of EMAT. The pulsed-echo waveforms of an aluminum alloy specimen are measured by the present EMAT in high temperatures and shear wave velocity of the specimen at each temperature is evaluated. Back-echo signals can be identified at the range of temperature from RT to 400 degrees C.