Investigation of Precipitation Hardening of LM22 by Nondestructive Methods

Apart from traditional application of nondestructive eddy current technique for determination of discontinuities, the method has been recently used to study aging process of 319aluminum alloys manufactured by casting. In this paper, the application of eddy current and conductivity methods for characterization of aging process has been investigated. A relation between mechanical properties and various parameters such as impedance, phase angle and voltage has been established. This study shows that the best results (R2 = 0.784) can be achieved using 110kHz frequency which leads to reversely relationship between Vickers hardness and normalized impedance, in other words maximum value in hardness-time curve coincide to minimum value in impedance-time curve. Results of hardness, conductivity and transmission electron microscope images are in agreement with this result.

Keywords:

Precipitation hardening , Eddy current method , Normalized impedance , Conductivity , Aluminium 319