<title>Experimental study of temperature dependence of reflectivity and heat capacity of steels and alloys at continuous wave Nd:YAG laser heating</title>

Abstract

A new method based on a combination of pyrometer and integrating sphere is proposed, allowing an express registration of temporal dependences of temperature, T(t), reflectivity, R<SUB>lambda</SUB>(t), and absorptivity, A<SUB>lambda</SUB>(t), of heat-conducting samples, when heated by continuous wave laser radiation. Computer-controlled acquisition and processing of these signals gives a possibility to obtain temperature dependences R<SUB>lambda</SUB>(T) and A<SUB>lambda</SUB>(T). In addition, a processing recorded by this method T(t) signal at cyclic heating and cooling of the 'thermally thin' sample (when laser beam is chopped periodically) allows us to find a temperature dependence of heat capacity C<SUB>p</SUB>(T). Thus both the A<SUB>lambda</SUB>(T) and C<SUB>p</SUB>(T) dependences have been obtained simultaneously during the same laser heating in the range of temperatures beginning from the initial (room) temperature up to melting point or even above for iron, steels and other alloys, when heated by cw Nd:YAG laser radiation with wavelength lambda equals 1064 nm in vacuum, air and inert gas atmosphere at heating rates in the range 10<SUP>3</SUP> divided by 10<SUP>4</SUP> K/s. Experimental set-up and the proposed experimental technique are described. An analytical estimation of laser overheating of front surface compared with rear surface of the sample is given to prove a validity of the proposed method of heat capacity measurement.