Analysis of Acoustic Emission Signals during Tensile Deformation of Fe-Si Steels with Various Silicon Contents

A systematic investigation was performed on the deformation mechanism of Fe-Si steels with various silicon contents (2, 3, and 4.5 wt pct Si) by analyzing frequency distribution of acoustic emission (AE) coupling with fracture surface observation. AE signals were recorded during tensile tests at room temperature (RT) and at an elevated temperature of (473 K) 200 °C. The results showed that both yield strength and tensile strength of Fe-Si steels increased with increasing silicon contents, whereas failure strain decreased. Increasing silicon content also increased the brittle fracture mode of the steels, especially at RT. In contrast, all specimens failed by ductile fracture mode at 473 K (200 °C). Frequency analysis showed that AE signals generated during tensile deformation were mainly distributed into two ranges, i.e., low (250 to 550 kHz) and high (550 to 750 kHz) frequency ranges. These generated AE signals were correlated with various types of observed deformation mechanisms. The low and high frequency signals corresponded to breaking and/or debonding of inclusions and twinning/cleavage fracture.