THERMAL-STABILITY OF ZR-BASED GLASSY ALLOYS EXAMINED BY ELECTRICAL-RESISTANCE MEASUREMENT

The effects of the thermal histories during the sample preparation and in measuring the physical properties on thermal stabilities of glassy Zr60Al15Ni25 and Zr60Al15Ni7.5Co2.5Cu15 alloys were examined mainly b y the electrical resistance measurement. As long as the present experi ments are concerned, the glass transition and crystallization temperat ure were not significantly affected by the thermal histories as for as -quenched samples. The temperature derivative of the electrical resist ance dR/dT exhibited a negative value below the glass transition tempe rature. In the contrast, dR/dT was turned to a positive value in the s upercooled liquid region. Although dR/dT showed an almost constant val ue for glassy Zr60Al15Ni25 ahoy, an apparent two step change was obser ved for glassy Zr60Al15Ni7.5Co2.5Cu15 alloy in the supercooled liquid region. It was found out that the dR/dT in the supercooled liquid regi on was significantly affected by the thermal history, especially the a tmosphere in measuring the electrical resistance. Even for the sample where the oxide layer of the surface was taken away by mechanical peri shing and the resistance measurement was carried out in the vacuum, th e dR/dT retained a small positive value in the supercooled liquid regi on.