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，对高温下金属凝固过程的监测提出了很高的要求。EMAT(电磁声学换能器)提供非接触式测量，适用于高温测量。影响EMAT工作温度的主要因素是铁轭的居里温度。在本研究中，我们建议使用空芯线圈作为EMAT的偏置磁源。用该方法测量了铝合金试件在高温下的脉冲回波波形，并估算了试件在各温度下的剪切波速。在从RT到400摄氏度的温度范围内，可以识别回波信号。

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.