Acoustic Emission of Pure Iron and Low-level Iron-Carbon Alloys During Plastic Deformation.

The acoustic emission (AE) of pure iron during plastic deformation increases with increasing plastic strain acceleration. Hence the AE is a function of the velocity and density of dislocations and of their time derivatives. The AE of quenched iron and iron-carbon specimens increases with grain size. Higher quenching temperatures reduce the AE during a subsequent tensile test. The reduction is greater for iron than for alloys. Within the limits of experimental error, the AE of Fe-C alloys is independent of the carbon content up to 200 ppm. Below room temperature, a very strong AE is caused by inhomogeneous deformation. Single crystals, especially those with edge orientation, have a stronger AE than polycrystals.