Transient conductance measurements and heat-flow analysis of pulsed-laser-induced melting of aluminum thin films

We report time-resolved electrical-resistance measurements during pulsed-laser melting of a metal, aluminum. The resistances are correlated with the thresholds for partial and full melting. We describe a semi-analytic solution, based on an impulse-response function, for the response, to a heating pulse, of a thin film of good thermal conductor supported by an infinite substrate. The results agree well with the resistance measurements, and confirm our interpretation of the data. In addition, time-resolved reflectance measurements establishing that, in this geometry, melting and solidification proceed via the motion of a well-defined, planar liquid/solid interface, whose position can be deduced from the resistance measurements. These measurements permit the first real-time determinations of melt-depths and quenching histories during rapid-solidification processing of metals.