Wilson John W, Jolfaei Mohsen A, Fletcher Adam D, Slater Carl, Davis Claire, Peyton Anthony J
Department of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, UK.
Warwick Manufacturing Group, University of Warwick, Coventry CV4 7AL, UK.
Sensors (Basel). 2024 Sep 20;24(18):6077. doi: 10.3390/s24186077.
Although much information can be gained about thermally induced microstructural changes in metals through the measurement of their thermophysical properties using a differential scanning calorimeter (DSC), due to competing influences on the signal, not all microstructural changes can be fully characterised this way. For example, accurate characterisation of recrystallisation, tempering, and changes in retained delta ferrite in alloyed steels becomes complex due to additional signal changes due to the Curie point, oxidation, and the rate (and therefore the magnitude) of transformation. However, these types of microstructural changes have been shown to invoke strong magnetic and electromagnetic (EM) responses; therefore, simultaneous EM measurements can provide additional complementary data which can help to emphasise or deconvolute these complex signals and develop a more complete understanding of certain metallurgical phenomena. This paper discusses how a DSC machine has been modified to incorporate an EM sensor consisting of two copper coils printed onto either side of a ceramic substrate, with one coil acting as a transmitter and the other as a receiver. The coil is interfaced with a custom-built data acquisition system, which provides current to the transmit coil, records signals from the receive coil, and is controlled by a graphical user interface which allows the user to select multiple excitation frequencies. The equipment has a useable frequency range of approximately 1-100 kHz and outputs phase and magnitude readings at a rate of approximately 50 samples per second. Simultaneous DSC-EM measurements were performed on a nickel sample up to a temperature of 600 °C, with the reversable ferromagnetic to paramagnetic transition in the nickel sample invoking a clear EM response. The results show that the combined DSC-EM apparatus has the potential to provide a powerful tool for the analysis of thermally induced microstructural changes in metals, feeding into research on steel production, development of magnetic and conductive materials, and many more areas.
尽管通过使用差示扫描量热仪（DSC）测量金属的热物理性质，可以获得许多关于热诱导金属微观结构变化的信息，但由于对信号存在多种相互竞争的影响，并非所有微观结构变化都能通过这种方式得到全面表征。例如，由于居里点、氧化以及转变速率（进而转变幅度）导致的额外信号变化，合金钢中再结晶、回火以及残余δ铁素体变化的准确表征变得复杂。然而，已表明这些类型的微观结构变化会引发强烈的磁和电磁（EM）响应；因此，同步进行的EM测量可以提供额外的补充数据，有助于突出或解卷积这些复杂信号，并更全面地理解某些冶金现象。本文讨论了如何对DSC仪器进行改装，以集成一个EM传感器，该传感器由印刷在陶瓷基板两侧上的两个铜线圈组成，一个线圈用作发射器，另一个用作接收器。该线圈与定制的数据采集系统相连，该系统向发射线圈提供电流，记录接收线圈的信号，并由图形用户界面控制，该界面允许用户选择多个激励频率。该设备的可用频率范围约为1 - 100 kHz，以每秒约50个样本的速率输出相位和幅度读数。对镍样品在高达600°C的温度下进行了同步DSC - EM测量，镍样品中可逆的铁磁到顺磁转变引发了明显的EM响应。结果表明，组合式DSC - EM仪器有潜力为分析金属中的热诱导微观结构变化提供强大工具，可应用于钢铁生产研究、磁性和导电材料开发以及更多领域。
