Acoustic emission from structural steels and Fe–C alloys

The acoustic emission released during the tensile testing of two structural steels (BS 4360 grades 50D and 50DM) and a series of Fe–C alloys (carbon contents in the range 0·1–1·3 wt-%) has been monitored using equipment with facilities for measuring the ringdown count, the event count, the rms voltage, and the amplitude distribution. The microstructure and the cracking of brittle phases were studied by light and scanning electron microscopy and correlated with the acoustic data. In particular, it was found that the inclusions in the steels and the grain-boundary proeutectoid cementite in the hypereutectoid alloys were responsible for these materials being more copious emitters than the hypoeutectoid alloys.