Depth profile reconstruction of the thermal conductivity of inhomogeneous solids: application to laser-hardened Al alloys

Photoacoustic measurement techniques can be used to determine thermal properties on and below the sample’s surface, thus subsurface thermal inhomogeneities, such as continuous profiles of thermal parameters, become measurable by photoacoustic methods. In this paper, the study is focused on the quantitative characterization of material modifications in subsurface layers of laser-hardened Al alloy samples. The variation of surface temperature is measured by PA technique. Then a new numerical algorithm, carried out by employing the pulsed spectrum technique and the regularization method, is used to reconstruct thermal conductivity depth profiles. The experiment results demonstrate that the experiment and the algorithm are very effective for microstructure depth profile reconstruction by nondestructive method. Received: 18 February 2000 / Accepted: 28 February 2000 / Published online: 30 June 2000